JP4826907B2 - Winding type vacuum deposition method and apparatus - Google Patents

Description

  The present invention relates to a winding-type vacuum deposition method and apparatus for forming a thin film on a film substrate that is wound by a heating evaporation method using an electron beam.

  2. Description of the Related Art In recent years, development of films in which various functions are provided by forming a thin film on the surface of a flexible base material such as plastic has been actively performed. In particular, when a thin film made of a metal oxide such as AlOx, SiOx, or MgO is formed on a base film under optimum conditions, the transparency and gas such as oxygen and water vapor can be obtained without impairing the flexible performance of the film. The film has a blocking function, and is used in a wide range of fields such as food packaging materials, electronic material packaging materials, and medicine packaging.

FIG. 4 is a schematic cross-sectional view showing a take-up vacuum deposition apparatus that heat-deposits on a flexible film substrate with an electron beam.
In FIG. 4, the evaporating material can be heated and evaporated by irradiating the evaporating material 2 inserted into the crucible 1 made of a material having a large heat resistance and heat capacity with an electron beam of high energy. The film substrate 4 unwound from the unwinding roll 3 is conveyed to the film forming drum 5. In the film forming chamber 6, the evaporation material 2 is thinly laminated on the film substrate 4 in the film forming chamber 6, and is taken up by the take-up roll 7 after leaving the film forming drum 5. The film forming drum 5 has a normal temperature of 0 ° in order to prevent the base material from being deformed by the release gas generated by the heat generated in the evaporation process from the film base material 4 and the heat rays radiated from the crucible 1 and the evaporation material 2. Cooling is adjusted to around C to -20 ° C. Furthermore, a ceramic thin film of oxide or nitride can be formed by introducing a reactive gas such as oxygen or nitrogen during evaporation in the film formation chamber during the evaporation process.

In general, a substrate deposited by an electron beam loses energy when an electron beam emitted from an electron gun collides with a crucible, but some of the electrons recoil and scatter and strike the film substrate. It is. For this reason, the electrostatic force acts when the film substrate 4 is charged and peeled off from the film forming drum 5. If the take-up tension overcomes this force, the film substrate 4 is peeled off from the film-forming drum 5 and can be wound. However, if it cannot be overcome, the film is wound around the film-forming drum and cannot be wound.
Even when the film can be wound, a discharge corresponding to the electrostatic force occurs at the interface between the film forming drum 5 and the film base 4 at the time of peeling, and the film base 4 is damaged such as a discharge mark (pinhole). In addition, since the winding tension becomes unstable, it is extremely difficult to wind the formed film without applying stress such as wrinkles. In particular, when the thin film to be produced is a metal oxide, it becomes a dielectric, so that electric charges are likely to accumulate, causing further winding troubles.

In order to cope with such a problem, many methods have been devised to reduce the electrostatic force at the peeling site on the film formation drum 5, but in order to improve this problem, recoil / scattering that causes charging. It is necessary to neutralize the electrostatic force by suppressing the charge or by ejecting the ionized particles in a state where the charge is drawn to the film surface by reducing the electrostatic capacity of the film forming drum (see, for example, Patent Document 1). The role of these ions is to alleviate the electrostatic force by neutralizing electrons that cause charging before reaching the film substrate or on the film substrate.
JP 2000-313953 A

However, the method of neutralizing the electrostatic force by injecting ionized particles requires a discharge device for generating ions, and there is a problem that increases the cost of the device and increases the size. Since the optimal conditions for neutralization change, there is a problem that countermeasures must be taken.
In general, an inert gas such as ionized argon gas or neon gas is used as an introduction gas necessary for the discharge device so as not to cause a chemical reaction with the film formation surface, but these gases are discharged, This is a gas necessary for alleviating the electrostatic force, and is exhausted by the exhaust pump without being reacted or adsorbed, which causes a significant pressure increase in the film formation atmosphere.
As a countermeasure for avoiding this, a method of separating gas by providing a partition plate, an intermediate chamber, or the like between the peeling site and the winding chamber 10 and the film forming chamber 6 has been proposed. And forced remodeling of existing equipment.

  Therefore, the present invention suppresses the charging trouble of the film base as much as possible when performing electron beam evaporation while avoiding problems such as the above-mentioned significant modification of the existing equipment, increase in equipment cost, and large scale, and stable without damage. An object of the present invention is to provide a winding type vacuum deposition method and apparatus capable of performing a typical film forming operation.

In order to achieve the above-described object, the winding-type vacuum deposition method of the present invention unwinds a film substrate in a vacuum, deposits a metal oxide on the film substrate traveling on a film forming drum, and A winding-type vacuum deposition method for winding the film substrate on which oxide is deposited, wherein a permanent magnet is installed inside the film formation drum in the vicinity of the film substrate being peeled from the film formation drum, The counter electrode of the film forming drum is a chamber outer wall, and a high frequency potential of 40 kHz to 100 kHz is applied to the film forming drum.
Further, the winding type vacuum deposition apparatus of the present invention unwinds a film substrate in a vacuum, deposits a metal oxide on the film substrate running on a film forming drum, and deposits the metal oxide on the film. A take-up vacuum deposition apparatus for winding a substrate, wherein a permanent magnet is installed inside the film-forming drum in the vicinity of the film substrate being peeled from the film-forming drum, and a counter electrode of the film-forming drum is The outer wall of the chamber is characterized in that a high frequency potential of 40 kHz to 100 kHz is applied to the film forming drum.

According to the winding type vacuum evaporation method and apparatus of the present invention, a permanent magnet is provided inside the film forming drum in the vicinity of the peeling site in order to remove the electric charge adhering to the base material after film forming and easily peel it off. By applying a high frequency to the film forming drum, the drum is made into a cathode, and a magnetron discharge is generated in the vicinity of the film forming drum so that the film can be irradiated with plasma immediately after leaving the film forming drum. Thus, it is possible to perform a stable film-forming operation without damage without causing problems such as a large remodeling of an existing facility, an increase in apparatus cost, and an increase in scale.
In particular, by applying a high frequency potential of 40 kHz to 100 kHz to the film forming drum, a high frequency potential can be applied to the film forming drum by stable continuous discharge. In addition, by setting the pressure band where the film base material peels from the film forming drum to 10 ⁻¹ Pa or less, maintaining an appropriate discharge and keeping the film forming pressure low and maintaining an environment free from impurities. Is possible.

Hereinafter, embodiments of the present invention will be specifically described.
FIG. 1 is a schematic sectional view showing an example of a winding type vacuum vapor deposition apparatus according to an embodiment of the present invention. In addition, the same code | symbol is attached | subjected and demonstrated for the structure which is common in the prior art example shown in FIG.
In FIG. 1, a take-up vacuum deposition apparatus 8 has upper and lower chambers of a take-up chamber 10 and a film forming chamber 6, and an upper take-up chamber 10 has an unwind roll 3, a take-up roll 7, and a film forming drum. 5 is arrange | positioned and the film base material 4 is drive | moving between them. Since the film forming drum 5 is installed due to factors such as cooling and rotation, it often has an installation potential for discharge.
On the other hand, the vapor deposition material 2 disposed in the lower film formation chamber 6 is heated and evaporated by the electron beam 9 generated from the electron gun 14. In addition, the winding chamber 10 and the film forming chamber 6 are each evacuated by an exhaust pump 11.
A permanent magnet 13 is disposed inside the film forming drum 5 in the vicinity of the peeled portion of the area 12 where the film substrate 4 that has traveled after forming a thin film in the film forming chamber 6 is separated from the film forming drum 5. Is fixed so as not to rotate with the rotation of the film forming drum 5.
The film forming drum 5 (cathode) as a counter electrode is only required to be high-frequency grounded with a copper plate or the like. As a suitable means, the chamber outer wall 20 and the cover 19 separated from the film forming drum 5 by a certain distance are used. By disposing, the discharge state can be further stabilized.

  Next, the permanent magnet will be described. As the material of the magnet, a neodymium-iron-boron or samarium-cobalt ferromagnetic material is used, and samarium-cobalt is more preferable in consideration of thermal stability. Further, the magnetic field intensity on the surface of the film forming drum is set to 200 to 450 gauss, and the magnetic yoke material used for separating the magnets is preferably a nonmagnetic stainless material or aluminum.

Usually, in an environment without a magnetic field, an inert gas is introduced into a position where the film substrate 4 is peeled from the film forming drum 5 and the pressure in the vicinity of the peeled position is temporarily increased, whereby Paschen's law V = f ( p × d) (V is the discharge start voltage [V], f is a function determined by the pressure p [Pa] and the inter-discharge distance d [m]), and the discharge start voltage V can be reduced.
Since the discharge start voltage V is a law that takes the minimum value as the product of the pressure p and the inter-discharge distance d, if it is assumed that the inter-discharge distance d is constant, the discharge start voltage V is determined only by the pressure p. By reducing V, the voltage can be lowered to a level that does not damage the film substrate 4 or the thin film, and discharge can be caused, and discharge at an energy that causes charging failure can be suppressed. However, when an inert gas is introduced into the vacuum apparatus, the pressure inside the vacuum chamber rises and a load is applied to the exhaust pump, and at the same time, the process film forming environment is adversely affected.

Therefore, the present embodiment is characterized in that the discharge can be continued by the gas staying in the electron vacuum chamber by the magnetic field without introducing the inert gas introduced for the discharge.
This is because a permanent magnet is arranged inside the film forming drum 5 and a high frequency potential of 40 to 100 kHz is applied to the film forming drum 5 so that the film forming drum 5 becomes a cathode, its magnetic field lines are closed, and a part of the magnetic field lines are formed. Since it is parallel to the roll surface of the film drum 5, the gas staying in the vacuum device in the vicinity of the peeling site is ionized and turned into plasma, and so-called magnetron discharge in which the current is closed by trapping electrons in the magnetic field is sustained. Because.
In addition, since this discharge repeatedly collides efficiently with electrons and ions, the discharge can be continued even in the pressure range where the mean free path is large: 10 ⁻² Pa, so that the film forming process pressure is not affected. . In addition, as another alternative method, an apparatus having a mechanism for relaxing charging attached to the film by arranging a discharge electrode and a gas introduction system in the vicinity of the film forming drum 5 has been developed. It must be arranged on the front and back of the film substrate, and the effect cannot be exhibited because the electrode cannot be arranged at the peeling location.
In this embodiment, the pressure at which the discharge can be started is kept low, the film is not rubbed by the discharge electrode, and the glow discharge can be stably caused at the peeling site. Winding is possible in a state where no charging failure occurs.

The film base 4 used here is polyolefin (polyethylene, polypropylene, etc.), polyester (polyethylene terephthalate, polyethylene naphthalate, etc.), polyamide (nylon-6, nylon-66, etc.), polystyrene, ethylene vinyl alcohol, poly Examples thereof include, but are not limited to, vinyl chloride, polyimide, polyvinyl alcohol, polycarbonate, polyethersulfone, acrylic, and cellulose (such as triacetyl cellulose and diacetyl cellulose). Evaporation material 2, various metals (e.g. Al, Cu, Ti, Si, etc.), _{or, TiO 2, MgO, SiO 2} , SiO, Al 2 O 3, ZrO 2, although ceramics ZnS and the like, especially No limitation.

Next, the reason why a high frequency of 40 to 100 KHz is desirable for the voltage applied to the film forming drum 5 in the present embodiment will be described.
In general separation, there are discharge using a high frequency of 100 KHz or more (hereinafter referred to as high frequency discharge) and discharge at a frequency lower than that (hereinafter referred to as low frequency discharge).
Low-frequency discharge is a discharge maintained by electron impact ionization (α effect) in the discharge space and secondary electron emission (γ effect) caused by collision of charged particles at the electrode. In order to show a changing direct current discharge behavior, a discontinuous discharge state may occur in a remarkably low frequency discharge (40 KHz or less) (see, for example, Yoshinobu Kawai latest plasma generation technology (IPC) P62).
Therefore, a complicated matching circuit is not required in the high frequency band of 40 to 100 KHz.

On the other hand, when the angular frequency of the electric field is increased, in a high frequency discharge that does not allow heavy ions (positive ions) to follow the rapid electrolysis change, the ions cannot reach the electrode and reciprocate in the discharge space. Since the discharge is maintained by the displacement current between the plasmas, it is necessary to consider the plasma space as one load (impedance). In addition, since the behavior (radiation) of radio waves cannot be ignored at high frequencies, and the load status changes every moment, it is necessary to constantly monitor the load status and allow the maximum current to flow from the power source. A device that matches the impedance of the power supply and the impedance of the power supply side (same values) is necessary and complicated (for example, see Brian N. Chapman, Plasma Processing Basics (Electrical Shoin) P139-141).
As a result, in the present embodiment, a high frequency of 40 to 100 KHz is used as the voltage applied to the film forming drum 5.

Next, in this Embodiment, the pressure zone of the location where a film base material peels from a film-forming drum shall be 10 < ^-1 > Pa or less. The reason will be described (for example, see Tsutsui Nobuto, Plasma Basic Engineering (Uchida Otsukuru), P38-40).
First, when the interval between two parallel electrodes is d, the internal pressure is P, and a voltage Vs is applied between the electrodes, the voltage at which discharge is started has a minimum value with respect to the term P × d. . This is because if the P is lowered, the electron mean free process becomes longer, the acceleration due to the electric field is larger, and impact ionization becomes more prominent. Since the number of collisions decreases, collision ionization becomes inactive and the discharge start voltage rises again.
In general, in a discharge using a magnetron, electrons are trapped between electrodes by the effect of a magnet, so that the number of collisions increases and the discharge can be maintained even when the pressure is low.
In general, in order to form a high-density film in the vapor deposition process, it is necessary to maintain an environment in which the deposition pressure is kept low and impurities are not mixed, so that it is as low as possible in the peeling discharge suppression process adjacent to the vapor deposition process. Discharge under pressure is desirable.

Examples of the present invention will be specifically described below together with comparative examples.
First, as Example 1, a PET (polyethylene terephthalate) film having a thickness of 12 μm was selected as a film base material, and an oxygen mass was irradiated with an electron beam with an acceleration voltage of 40 kV and 12 kW to melt and evaporate oxygen. A gas was introduced to form an alumina thin film on the film substrate at a speed of 60 m / min.
As shown in FIG. 2, the permanent magnet 13 made of samarim-cobalt alloy is arranged on the film forming drum in such a manner that the internal S pole 17 is surrounded by the N pole 16 via the yoke 18, and the film forming drum is arranged. Film formation was performed while applying a high frequency of 40 kHz. Here, when the magnetic force in the vicinity of the surface of the film forming drum was measured with a gauss meter, it was about 200 gauss.

Next, as a comparative example 1, a PET (polyethylene terephthalate) film having a thickness of 12 μm is selected as a film base material, and an aluminum beam is irradiated with an acceleration voltage of 40 kV and 12 kW to melt and evaporate in an environment. Oxygen gas was introduced to form an alumina thin film on the film substrate at a speed of 60 m / min.
A PET tube having a diameter of 6 mm fixed so as to be sprayed toward the peeling surface is disposed in an area between the film running surface (deposition back surface) and the film forming roll, and 2 from the gas ejection holes having a diameter of 1 mm and a pitch of 10 mm. Film formation was performed while introducing argon gas of × 10 ⁻⁴ m ³ / min.
Further, as Comparative Example 2, film formation was performed and evaluated using the same apparatus as Comparative Example 1 on the condition that water vapor and argon gas were not introduced into the liquid vapor injection port.

Next, evaluation of Example 1 and Comparative Examples 1 and 2 will be described.
(1) Aluminum oxide layer oxygen permeability: The film is measured in an atmosphere of 40 ° C.-90% RH using an oxygen permeability meter (MOCON OXTRAN) manufactured by Modern Control.
(2) Pinhole of aluminum oxide layer: A strong penetrating liquid is sprayed from the thin film surface side, permeated, and visually observed to see if it exudes to the back surface.
(3) Film winding shape: The wound web is visually observed, and the amount of winding deviation caused by wrinkles caused by wrinkles and winding caused by winding tension instability is measured with a ruler.
(4) Scratch on the back surface of the film: The raw film on which the film has been wound is wound off, and vertical scratches in the winding direction of the film on which the film has been formed are visually observed.
(5) Pressure during alumina film formation: A hot cathode ionization gauge (ion gauge) is used to observe the pressure in the film formation chamber and the winding chamber during alumina deposition.

FIG. 3 is a list showing the evaluation results of Example 1 and Comparative Examples 1 and 2.
When a strongly permeable liquid was sprayed on each AlOx thin film having a thickness of 80 to 120 nm, almost no oozing was confirmed in Example 1 and Comparative Example 1, but in the Comparative Example 2, the liquid oozed over a wide range. It was confirmed that there were very many pin poles. Further, in Example 1 and Comparative Example 1, a gauge band due to film wrinkles that normally occurs during winding is not seen, the amount of winding deviation is as good as about ± 1 mm, and further, the film is wound on the back surface of the wound film. Longitudinal wounds were not observed. However, in Comparative Example 2, many vertical flaws derived from the liquid vapor injection holes were observed, and the film was caught in the tube, resulting in poor winding.

Further, when the peeled surface during film formation was observed, glow discharge that emitted light thinly was observed around the peeled surface in Example 1 and Comparative Example 1, and the film after film formation was peeled off without contacting the gas injection holes. In Comparative Example 2, it was confirmed that the film was in contact with the flexible tube in which the film and the gas injection holes were arranged, and strong discharge luminescence was seen along the peeling surface, and the peeling portion was It was in an unstable state of moving back and forth.
This is due to the fact that the electrostatic force accumulated in large quantities is accompanied by a strong discharge emission and releases the energy instantaneously at a time to loosen the film. It is thought that wrinkles occurred.

  In addition, in the oxygen barrier property, it was confirmed that there was an effect of suppressing winding defects and reducing pinholes by introducing an inert gas to perform discharge. It was confirmed that Comparative Examples 1 and 2 were inferior to 1. As a cause of this, there is a tendency to reduce the pressure in the film forming chamber as much as possible in order to improve the film properties (especially water vapor barrier properties) of the metal oxide, and the above-mentioned tendency is confirmed also in this evaluation result. Compared to the case where easy separation is realized by introducing only a large amount of inert gas and lowering the discharge start voltage, the pressure increase in the deposition chamber is further suppressed by reducing the minimum gas flow required for discharge. It is possible that the gas shutoff performance has been improved.

As described above, according to the present embodiment, in a winding type vacuum deposition method in which a thin film is formed by heating and evaporation with an electron beam on a film substrate that is wound and traveled, scattered electrons and secondary electrons generated from the electron beam are used. This can improve the problem that extremely high electrostatic energy is released which damages the film when the film enters the film substrate and the substrate film is peeled off from the film forming drum.
In general, in order to release the accumulated electrostatic energy without difficulty, it is necessary to increase the pressure in the vicinity of the area to be peeled to a level of several Pa. However, if a normal inert gas is introduced, the pressure in the film forming chamber also increases, which greatly affects the film forming environment (in general, when the pressure in the film forming chamber increases, the average of evaporated molecules The free process becomes smaller, the energy that collides with the substrate film becomes smaller, the adhesion failure to the substrate occurs, and the function of the membrane may be lost because the film becomes sparse (porous). Many).

However, in this embodiment, in order to remove the electric charge adhering to the base material after film formation and easily peel, a permanent magnet is provided inside the film formation drum in the vicinity of the separation point, and a high frequency is applied to the film formation drum. When applied, the drum becomes a cathode, and a magnetron discharge is generated in the vicinity of the film-forming drum, so that plasma irradiation can be performed immediately after the film leaves the film-forming drum. In addition, it is possible to perform ionization by using the gas (gas such as oxygen or water vapor) remaining and adsorbed in the vacuum chamber without introducing an inert gas compared to the conventional method. Glow discharge can be maintained without affecting the pressure.
Furthermore, there is no need for a gas introduction pipe or a cylindrical discharge electrode, which was conventionally necessary for removing the charge on the back surface of the film, thereby suppressing the back surface of the film from rubbing and causing significant scratches. It becomes possible.

It is a schematic sectional drawing which shows an example of the winding type vacuum evaporation system by embodiment of this invention. It is sectional drawing which shows the detail of the permanent magnet arrange | positioned in the film-forming drum of the winding type vacuum evaporation system shown in FIG. It is a list which shows the evaluation result of Example 1 and Comparative Examples 1 and 2 of the present invention. It is a schematic sectional drawing which shows an example of the winding type vacuum evaporation system by a prior art.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Crucible, 2 ... Deposition material, 3 ... Unwinding roll, 4 ... Film base material, 5 ... Film-forming drum, 7 ... Winding roll, 8 ... Winding type vacuum evaporation apparatus, 9 ...... Electron beam, 10 …… Winding chamber, 11 …… Exhaust pump, 13 …… Permanent magnet, 14 …… Electron gun, 20 …… Chamber outer wall.

Claims (6)

A roll-up vacuum deposition method in which a film substrate is unwound in vacuum, a metal oxide is deposited on the film substrate traveling on a film formation drum, and the film substrate on which the metal oxide is deposited is wound up. There,
A permanent magnet is installed inside the film forming drum in the vicinity of the film base material peeling from the film forming drum, and the counter electrode of the film forming drum is used as an outer wall of the chamber.
A high frequency potential of 40 kHz to 100 kHz is applied to the film formation drum.
A winding type vacuum vapor deposition method characterized by the above. The winding type vacuum vapor deposition method according to claim 1, wherein the pressure band where the film substrate peels from the film forming drum is 10 ^-1 Pa or less. A roll-up vacuum deposition apparatus that unwinds the film substrate in a vacuum, deposits a metal oxide on the film substrate traveling on the film formation drum, and winds up the film substrate on which the metal oxide is deposited. There,
A permanent magnet is installed inside the film formation drum in the vicinity of the film base material peeling from the film formation drum, and the counter electrode of the film formation drum is a chamber outer wall,
A high frequency potential of 40 kHz to 100 kHz is applied to the film formation drum.
A wind-up type vacuum evaporation apparatus characterized by that. The winding type vacuum deposition apparatus according to claim 3, wherein a pressure zone where the film base material peels from the film forming drum is 10 ⁻¹ Pa or less.   The winding-type vacuum deposition apparatus according to claim 3, wherein the permanent magnet is fixed so as not to rotate with the rotation of the film forming drum.   A crucible in which an evaporation material is inserted, an electron gun for irradiating the evaporation material with an electron beam, a film formation chamber in which the crucible and the electron gun are disposed, the film formation drum, an unwinding roll, and a winding roll; The winding type vacuum deposition apparatus according to claim 3, further comprising: a winding chamber disposed; and an exhaust pump for evacuating the film forming chamber and the winding chamber.

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