JP4380360B2 - Winding type vacuum evaporation system - Google Patents

Description

  The present invention relates to a take-up vacuum deposition apparatus for forming a thin film by heating and evaporating with an electron beam on a roll-up base, particularly a plastic film base.

  2. Description of the Related Art In recent years, film development has been actively conducted in which a thin film is formed on the surface of a base material such as plastic to provide functionality. As a typical example, a gas barrier film is added and applied to food packaging materials. A thin film made of a metal oxide such as AlOx, SiOx, MgO is formed on the film, and these are used because they are transparent and have gas barrier properties such as oxygen and water vapor. FIG. 2 shows the simplest conceptual diagram of a wind-up type vacuum deposition apparatus by electron beam heating for a film substrate represented by plastic.

  The evaporation material 18 is put in a crucible 17 having heat resistance, and is heated and evaporated by collision of high energy electrons with the evaporation material. The film substrate 12 unwound from the unwinding roll 13 is sent to the film forming roll 14. The film substrate 12 is vapor-deposited on the evaporation material 18 in the film forming chamber, and is taken up away from the film forming roll 14 to become a winding roll 15. The film forming roll 14 is cooled to reduce the floating of the film base 12 due to heat generated in the evaporation process. Furthermore, an oxide thin film or the like can be formed relatively easily by introducing a reactive gas such as oxygen during evaporation in the film formation chamber in this process, and is generally called reactive vapor deposition.

  When the film base 12 is unwound and a series of operations such as film formation and winding are performed, a tension to be peeled between the film base 12 and the film formation roll 14 is applied at the exit position of the film formation roll 14. However, a force that causes the film base 12 and the film forming roll 14 to adhere to each other due to electrostatic force acts in the opposite direction. If (tension> static force), the film base 12 is peeled off from the film forming roll 14 and wound up. At that time, the interface between the film forming roll 14 and the film substrate 12 generates a discharge corresponding to the electrostatic force and gives an impact to the film substrate 12. The impact causes inconveniences such as damage to the film substrate 12 or the thin film and unstable tension. With (tension <electrostatic force), the film base 12 is not peeled off from the film forming roll 14, and is not sent out from the film forming roll 12, so that the film base 12 can be wound up to the entrance of the film forming roll 14. In order to deal with such a problem, many methods have been considered to reduce the electrostatic force at the peeling site on the film forming roll 14. This electrostatic force is considered to be that scattered electrons, recoil electrons, etc. reach the film substrate 12 from the upper part of the evaporation material 18 by the electron beam. This can be expected from the fact that the electrostatic force is rapidly increased by irradiating the evaporation material with an electron beam. Furthermore, since a thin film to be generated is a dielectric when it is a metal oxide, scattered electrons and recoil electrons accumulate.

Patent documents are described below.
JP, 2000-313953, A It is conventionally considered to reduce electrostatic force by neutralization by ion (for example, refer to patent documents 1). The role of these ions is to reduce the electrostatic force by neutralizing electrons that cause charging such as charging before reaching the film substrate or on the film substrate. However, there is a problem that the optimum condition for ion neutralization varies depending on the necessity of an apparatus for generating ions and the film forming conditions.

  The present invention has been made in order to avoid the above-described problem, and eliminates the charging trouble of the film base material when performing electron beam evaporation, and can perform a stable film formation without damage. It aims at providing a vapor deposition apparatus.

To achieve the above objective,
The invention of claim 1 is a vacuum vapor deposition apparatus in which vapor deposition using an electron beam as a heating source can be performed on the substrate while conveying the substrate by winding.
The crucible containing the evaporation material is made of a dielectric, and a means for applying a positive potential from an external power source to the crucible charged to a negative potential by an electron beam is provided in the film formation chamber, and plasma is generated in the crucible and the film formation chamber. It is a winding type vacuum deposition apparatus characterized by being generated and maintained.

  The invention according to claim 2 is the winding type vacuum evaporation apparatus according to claim 1, wherein the potential of the crucible decreases when the plasma is generated by the means for applying the positive potential.

A third aspect of the present invention is the take-up vacuum deposition apparatus according to the first or second aspect, wherein the crucible is made of a ceramic sintered body.
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  A fourth aspect of the present invention is the take-up vacuum deposition apparatus according to the third aspect, wherein the ceramic sintered body contains aluminum oxide.

Invention of Claim 5 is a winding-type vacuum evaporation apparatus of any one of Claims 1-4,
A roll-up vacuum deposition apparatus characterized in that a base material transfer chamber and a film formation chamber are separated by winding, and the pressure in the base material transfer chamber is higher than the pressure in the film formation chamber.

Invention of Claim 6 is the winding-type vacuum evaporation apparatus of any one of Claims 1-5,
A wind-up type vacuum vapor deposition apparatus is characterized in that glow discharge is performed by a means for applying a positive potential to a crucible charged to a negative potential.

The invention of claim 7 is the winding type vacuum evaporation apparatus according to any one of claims 1 to 6,
In the film forming chamber, the means for deflecting the electron beam by the magnetic field simultaneously has a function of confining the plasma.

  According to the present invention, in a winding-type vacuum deposition apparatus for forming a thin film by heating and evaporating with an electron beam on a substrate for winding and traveling, particularly a plastic film substrate, the film in winding is reduced by reducing the potential increase in the crucible. Therefore, good characteristics can be obtained without damaging the deposited film. A simple device with a direct current power source and electrodes reduces the potential difference between the crucible and the film forming roll, so that the effect of reducing charging can be obtained. Further, since the abnormal discharge of the crucible is suppressed, the crucible can be prevented from being damaged by the abnormal discharge, so that the durability is improved. In addition, managing the potential of the crucible can be used to determine whether or not there is a charging failure.

Hereinafter, an embodiment of the present invention will be described. FIG. 1 is a cross-sectional view showing an example of a take-up vacuum deposition apparatus of the present invention. In the vacuum tank 11 of the wind-up type vacuum evaporation apparatus, a winding unit comprising a film forming roll 14 in addition to the winding roll 13 and the unwinding roll 15, a place where the film substrate 12 runs on the film forming roll 14 There is a thin film forming section called a film forming chamber. In order to put them in a vacuum environment, a vacuum pump 10 is provided for evacuating the winding unit and the thin film forming unit. In the part where the film substrate 12 that has traveled along the thin film forming section is separated from the film forming roll 14. Since the film forming roll 14 is often grounded due to factors such as cooling and rotation, it can always be a ground electrode against discharge. The thin film forming portion has an evaporation source composed of the evaporation material 18 and the crucible 17 and can be heated and evaporated by the electron beam 19 to form a thin film. The electron beam 19 is generated by an electron gun 16, and a general electron gun such as a thermionic emission type can be used as the electron gun 16. As described above, charging failure of a dielectric substrate such as a plastic film substrate, which is a problem due to conventional electron beam evaporation, is prevented.

As the film substrate 12, known materials can be used. For example, polyolefin (polyethylene, polypropylene, etc.), polyester (polyethylene terephthalate, polyethylene naphthalate, etc.), polyamide (nylon-6, nylon-66, etc.), polystyrene , Ethylene vinyl alcohol, polyvinyl chloride, polyimide, polyvinyl alcohol, polycarbonate, polyethersulfone, acrylic, cellulose-based (triacetylcellulose, diacetylcellulose, etc.) and the like are not particularly limited. Examples of the evaporation material 18 include various metals (for example, Al, Cu, Ti, Si, and the like), ceramics such as TiO ₂ , MgO, SiO ₂ , SiO, Al ₂ O ₃ , ZrO ₂ , and ZnS, but are not particularly limited. .

  Thus, when forming a thin film by the apparatus shown in FIG. 1, the film base 12 is placed like the unwinding roll 13, the evaporation material 18 is placed in the crucible 17, and the upper and lower vacuum chambers are vacuumed to an appropriate pressure. The pump 10 is evacuated. When the pressure capable of being irradiated with the electron beam 19 is reached, the electron gun 16 is operated to heat the evaporation material 18 until it evaporates, and the film base 12 is run on the film forming roll 14 to form a thin film of the evaporation material 18. Can do. Thereafter, the film substrate 12 is wound up like the winding roll 15. At this time, in addition to the evaporation material 18, scattered electrons and secondary electrons are incident on the film substrate 12, and an electrostatic force is applied when the film is peeled off from the film forming roll 14. At this time, paying attention to the energy that the electron beam 19 heats the evaporation material 18, the electron energy that reflects and diffuses, and the energy that charges the crucible, the film forming roll 14 that is equal to the ground potential from the charged potential of the crucible We thought that an electric field was formed toward the outer wall. Therefore, even a relatively low energy electron such as a reflected electron or a diffused electron repels the negatively charged crucible and accelerates toward the film substrate 12 on the film forming roll 14. The potential charged to the crucible is related to the acceleration voltage of the electron beam. An electron beam used in normal vacuum vapor deposition is about −10 kV to −40 kV, and is expected to be at least −several kV.

For this reason, in consideration of efficiently discharging negative charges, a positive potential is applied to the discharge electrode 22 placed around the crucible. Then, when the electron beam is incident, the discharge is started only by supplying a positive voltage of several tens of volts to the discharge electrode 22 from the DC power source 21. This discharge is glow plasma, and the current from the DC power source 21 maintains the plasma. Due to the stable glow plasma, the electric potential of the crucible is reduced, and the acceleration of the reflected electrons and scattered electrons from the crucible to the film forming roll 14 is suppressed. If the crucible is a ceramic sintered body, it is preferable because it has excellent thermal characteristics and high hardness as a crucible, but is charged because it is a dielectric. With the above contents, it is necessary to lower the crucible potential. Among ceramic sintered bodies, a crucible containing aluminum oxide as a component is a crucible having a relatively low dielectric constant (relative dielectric constant of about 10), high electrical insulation, and difficult to form an alloy with an evaporation material. More preferred. The reason why the pressure is increased on the winding chamber side in the film forming chamber and the winding chamber is to reduce the voltage of the peeling discharge when the charged film is separated from the film forming roll 14. The beam surface of the electron gun 16 and the surface of the evaporation material 18 are shifted by 90 °. Therefore, an electron beam deflection coil 20 is installed to deflect the beam surface by 90 °. The electron beam deflection coil 20 has an action of confining plasma generated by the crucible and the discharge electrode 22 in order to generate a strong magnetic field. The electrons rotate in the magnetic field, thereby deflecting the electron beam by 90 °. Similarly, the electrons in the plasma also rotate in the same direction. Therefore, it is preferable that collision with electrons is actively performed in the plasma space, so that more stable glow plasma is generated.

  Hereinafter, an embodiment of the present invention will be specifically described.

A PET (polyethylene terephthalate) film with a thickness of 25 μm as a film base, Al as an evaporation material, an electron beam with an acceleration voltage of 40 kV and 12 kW are generated from an electron gun, oxygen gas is put into the Al evaporation, and reactive deposition is performed An AlOx thin film was formed on a PET film running on a film forming roll at 60 m / min. The pressure was 2.0 × 10 ⁻¹ Pa in the film forming chamber and 1.5 Pa in the winding chamber. As shown in FIG. 3, the crucible was fixed by filling alumina powder as ceramic powder inside the crucible case. A 5 cm square stainless steel electrode (thickness: 0.3 mm) was put in the alumina powder, and taken out of the chamber by a lead wire protected with an insulator. The potential was measured with a voltmeter. Moreover, the film surface potential with an electrometer was measured at the place where the film was separated from the film forming roll. 150 V was applied from a direct current power source during film formation. The barrier performance was evaluated by measuring the potential of the crucible, the surface potential of the film, the film formed and its water vapor transmission rate. The water vapor transmission rate measurement was performed using a measuring apparatus: PERMATRAN 3/31 manufactured by Modern Control Co., Ltd .: 40 ° C.-90% RH.

  In order to compare the effect of the present invention with the same apparatus as in Example 1, voltage application from a DC power source was not performed, and Example 2 as a comparative example was evaluated in the same manner as Example 1. The results are shown below.

  In Example 1 of the present invention, the crucible potential and the surface potential of the film were applied with a stable potential at a small potential within 0.1 kV and ± 1.5 kV, respectively. However, in Example 2 as a comparative example, the electric potential varied widely, and there was a portion where the potential of the crucible reached -30 kV to -10 KV and the potential of the film reached -60 kV.

  In Example 1 of the present invention, a thin light emission was observed around the peeled surface, but the film was peeled off from the film-forming roll without any problem, and no wrinkles were found on the wound film. However, in Example 2 as a comparative example, strong discharge light emission was seen along the peeled surface, and the peeled portion moved back and forth. The electrostatic force released energy when a strong discharge luminescence was visible, causing wrinkles to loosen the film.

When the water vapor transmission rate in Example 1 of the present invention was measured, it showed a good barrier performance of 1.8 g / m ² -24 hr, but in Example 2 as a comparative example, 19.5 g / m ² -24 hr. As a result, barrier performance hardly appeared.

It is explanatory drawing which shows an example of the winding type vacuum evaporation system of this invention. It is explanatory drawing which shows the simplest structure of the conventional winding type vacuum evaporation system. It is explanatory drawing which shows an example of the crucible potential measurement of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Vacuum pump 11 ... Vacuum tank 12 ... Film base material 13 ... Unwinding roll 14 ... Film-forming roll 15 ... Winding roll 16 ... Electron gun 17 ... Crucible 18 ... Evaporating material 19 ... Electron beam 20 ... Electron beam deflection coil 21 ... DC power supply 22 ... Discharge electrode 23 ... Voltmeter 24 ... Crucible case 25 ... Ceramic powder

Claims (7)

In a vacuum deposition apparatus capable of performing deposition using an electron beam as a heating source on the substrate while conveying the substrate by winding,
The crucible containing the evaporation material is made of a dielectric, and a means for applying a positive potential from an external power source to the crucible charged to a negative potential by an electron beam is provided in the film formation chamber, and plasma is generated in the crucible and the film formation chamber. A wind-up type vacuum deposition apparatus characterized by being generated and maintained.   2. The winding type vacuum deposition apparatus according to claim 1, wherein when the plasma is generated by the means for applying the positive potential, the potential of the crucible decreases.   The winding type vacuum deposition apparatus according to claim 1 or 2, wherein the crucible is made of a ceramic sintered body.   The winding type vacuum vapor deposition apparatus according to claim 3, wherein the ceramic sintered body contains aluminum oxide. In the winding type vacuum deposition apparatus according to any one of claims 1 to 4,
A take-up vacuum deposition apparatus characterized in that a substrate transport chamber and a film forming chamber are separated by winding, and the pressure in the substrate transport chamber is higher than the pressure in the film forming chamber. In the winding type vacuum deposition apparatus according to any one of claims 1 to 5,
A wind-up type vacuum vapor deposition apparatus, characterized in that a discharge is performed by means for applying a positive potential to a crucible charged to a negative potential is glow discharge. In the winding type vacuum evaporation apparatus according to any one of claims 1 to 6,
A winding type vacuum vapor deposition apparatus characterized in that means for deflecting an electron beam by a magnetic field in a film forming chamber simultaneously has an action of confining plasma.

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