JP2013036104A - Method and apparatus for forming thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a thin film, in which a direct-current voltage is stably applied to a cooling roller to sufficiently cool the film to thereby prevent the thermal deformation of the film, in a film forming method of continuously feeding an insulating film in a reduced pressure atmosphere and vapor-depositing the thin film on the insulating film.SOLUTION: In the method for forming a thin film, a liquid having a volume resistivity of 1 MΩ-m or more and a kinetic viscosity in the range of +25 to -30°C of 200 mm/s or less is used as a coolant introduced into the cooling roller, thereby stably applying the voltage to the cooling roller and bringing the film into intimate contact with the cooling roller by electrostatic attraction to form the thin film.

Description

  The present invention relates to a thin film forming method and a thin film forming apparatus for continuously feeding an insulating film in a reduced-pressure atmosphere, depositing a thin film on the film while closely contacting the film with a cooling roller and cooling the film.

While winding a long raw material film continuously drawn out from an unwinding roll around a cooling roller, the evaporation material from the evaporation source disposed opposite to the cooling roller is vapor-deposited on the raw material film, and the raw material film after vapor deposition 2. Description of the Related Art A thin film forming apparatus that winds a film with a winding roller is known. (For example, see Patent Document 1)
In this type of thin film forming apparatus, in order to prevent thermal deformation of the film at the time of vapor deposition, the film forming process is performed while the film is in close contact with the peripheral surface of the cooling roller and cooled. The cooling roll circulates a cooling medium (refrigerant) in order to constantly cool the film. Therefore, in order to prevent thermal deformation of the film, how to ensure the adhesion of the film to the cooling roller is an important issue.

  Therefore, in the thin film forming apparatus described in Patent Document 1, an auxiliary roller that is in contact with the film-forming surface of the film is disposed between the cooling roller and the take-up roll, and a DC voltage is provided between the auxiliary roller and the cooling roller. A method is disclosed in which the film is electrostatically adhered to the cooling roller by applying. As a result, the adhesion of the film to the cooling roller is obtained, so that thermal deformation of the film during vapor deposition is effectively prevented. Patent Document 2 describes that ethylene glycol or silicone oil is used as a refrigerant to be introduced into the cooling roller.

JP 2006-152448 A JP 2010-242217 A

  However, in order to achieve the configuration described in Patent Document 1, it is necessary to electrically insulate the cooling roller and the auxiliary roller from the ground potential of the support housing. However, since the cooling roller cools the film, it is necessary to circulate the refrigerant. Even if the cooling roller is mechanically insulated and supported, an electric current flows to the ground through the refrigerant circulating through the inside and the piping equipment, It becomes difficult to apply a DC voltage stably to the cooling roller. For example, ethylene glycol, which is a refrigerant material described in Patent Document 2, is generally widely used as an antifreeze solution, but is mainly used in a state where the viscosity is lowered by diluting with water. (If not diluted, the viscosity is high and circulation is difficult). However, since the water-ethylene glycol solution is a conductive fluid, when it is used as a refrigerant for the cooling roller, if a voltage is applied by connecting a DC power source between the cooling roller and the auxiliary roller, the ethylene glycol solution inside the cooling roller Current flows through the metal pipes and metal joints toward the earth, and the current becomes ground-down and the voltage becomes 0V.

In order to prevent this problem, there is a method to insulate the refrigerant circulator and metal piping path itself together with the cooling roller and electrically disconnect it from the ground. It is not realistic because it requires constraints and excessive insulation equipment structure. Therefore, in order to apply a voltage to the cooling roller and the auxiliary roller, an insulating fluid refrigerant has been desired. The higher the volume resistance of the refrigerant, the better. The lower the volume resistance, the more current flows from the cooling roller through the refrigerant to the ground, and when the amount of current reaches the current capacity of the DC power supply, the applied voltage drops. Initially, the adhesive force gradually decreases and thermal deformation occurs in the deposited film. In this case, it is necessary to change to a DC power supply with a large current capacity that can withstand the current output loss. However, since the DC power supply with a large capacity is required as the volume resistance decreases, the power supply cost becomes very high. End up. Therefore, a refrigerant having a high resistance of 1 MΩ · m or more that can use a small DC power source has been desired.
In addition, the cooling capacity of the refrigerant is mainly determined by the thermal conductivity and the amount of circulation. However, when the refrigerant requires insulation, water cannot be mixed, and therefore, the viscosity is often high at low temperatures. The circulation of the high-viscosity refrigerant has a problem in that the load of the refrigerant circulator pump becomes excessive, and the circulation rate is reduced to lower the cooling efficiency. Therefore, in the range of + 25 ° C. to −30 ° C., which is a refrigerant temperature normally required for film cooling, a low viscosity refrigerant having insulating properties has been desired.

  For example, the silicone oil described in Patent Document 2 is an insulating fluid, but has a large viscosity increase at low temperatures and many problems with cooling performance at low temperatures. Had the problem of causing thermal deformation. Therefore, the present invention has been made in view of the above problems, and it is an object to form a thin film by preventing a thermal deformation of the film by applying a DC voltage stably to a cooling roller with simple equipment and sufficiently cooling the film. To do.

The present invention achieves the above object and is a thin film forming method for forming a thin film on an insulating film,
A vacuum chamber, transport means for transporting the film inside the vacuum chamber, a cooling roller for closely cooling the film in close contact with the film, and a thin film formed on the film disposed opposite to the cooling roller Forming film forming means, an auxiliary roller for contacting the film forming surface of the film to guide the film traveling, and a voltage applying means for applying a DC voltage between the cooling roller and the auxiliary roller. In the insulating film thin film forming means, the cooling roller is held in a state electrically insulated from the vacuum chamber by a support member, and has a volume resistivity of 1 MΩ · m or more in the roller, from + 25 ° C. A liquid cooling medium having a kinematic viscosity of 200 mm ² / s or less in a range up to −30 ° C. is circulated. The cooling medium is a liquid mainly composed of polysiloxane.

  As described above, since the cooling roller can be insulated with a simple structure by the thin film forming method of the present invention, a DC voltage can be applied stably at a low cost, and the film heat can be obtained by sufficiently cooling the film. It becomes possible to form a film while preventing deformation.

The figure which shows the structure of the thin film formation method in this invention, and the connection structure of DC bias power supply. The figure which showed about the cross-sectional structure of the roller for cooling, and the circulation path | route of a refrigerant | coolant in the state seen from the orthogonal | vertical direction toward the unwinding side roller from the center of FIG.

  Embodiments of the present invention will be described below with reference to the drawings. In the present embodiment, a general thin film forming method in which an evaporation source of vapor deposition material is used as a film forming source as the thin film forming means will be described as an example.

  FIG. 1 is a schematic configuration diagram of a thin film forming apparatus 1 of the present embodiment. The thin film forming apparatus 1 includes a vacuum chamber 10, an unwinding roll 11 that is a transporting means for the film 13, a transporting roller 14, a cooling roller 15, an auxiliary roller 18, and a winding roll 12. Further, an evaporation source 16 for vapor deposition material, which is a film forming means for forming a thin film on the film, is provided. The internal space of the vacuum chamber 10 is partitioned by a partition plate 19 into a chamber in which the unwinding roller 14 and the auxiliary roller 18 are installed, and a chamber in which the evaporation source 16 is disposed. Both chambers are each connected to a vacuum pump 50 and evacuated to a predetermined degree of vacuum.

  The film 13 is made of a long insulating film cut to a predetermined width. In the present embodiment, a PP (polypropylene) film, a PET (polyethylene terephthalate) film, a PPS (polyphenylene sulfide) film, a nylon film, a polyimide film, etc. A plastic film is used, but other insulating films, paper sheets, and the like are applicable.

The film 13 is unwound from the unwinding roll 11 and is wound on the winding roll 12 via a plurality of conveying rollers 14, a cooling roller 15, and an auxiliary roller 18.
FIG. 2 shows a configuration when viewed from a direction perpendicular to the respective rollers from the vicinity of the center in FIG. The vacuum chamber 10 is in close contact with the movable carriage 30 and sealed with a seal member 23 to form a vacuum closed space inside. The moving carriage 30 is provided with the unwinding roll 11, the conveying roller 14, the cooling roller 15, the auxiliary roller 18 (not shown), and the winding roll 12 (not shown) shown in FIG. It is supported freely. The movable carriage 30 is in close contact with the vacuum chamber 10 at the time of film formation, and can move in a direction away from the vacuum chamber 10 during the return to atmospheric pressure after completion of film formation. After the movement, the unwinding roll 11 and the winding roll 12 are moved. Can be removed and installed. FIG. 2 shows the internal structure of the cooling roller 15. The cooling roller 15 is a double-structured cylinder having an outer cylinder 24 outside the inner cylinder 25, and is made of a metal such as iron or stainless steel. The moving carriage 18 is provided with a refrigerant circulator 26. The refrigerant supply pipe 20 is connected from the refrigerant circulator 26 to one end of the inner cylinder 25, and the refrigerant is introduced into the inner cylinder 25 of the cooling roller 15. . The refrigerant introduced into the inner cylinder 25 circulates from the other end to the outer cylinder 24 side, and cools the surface of the cooling roller 15. The circulated refrigerant is discharged from the outer cylinder end on the introduction end side, returns to the refrigerant circulator 26 through the refrigerant discharge pipe 21. Inside the refrigerant circulator 26, a heat exchanger (not shown), a circulation pump 27, and a motor 28 for driving the circulation pump 27 are installed, the returned refrigerant is re-cooled to a predetermined temperature, and again from the refrigerant supply pipe 20. Discharge. Thus, the surface temperature of the cooling roller 15 is cooled to a predetermined temperature and adjusted by repeatedly circulating the refrigerant to the cooling roller 15.
The evaporation source 16 shown in FIG. 1 or FIG. 2 includes a mechanism for containing a vapor deposition material and heating and evaporating the vapor deposition material by a known method such as resistance heating, induction heating, or electron beam heating. The evaporation source 16 is disposed below the cooling roller 15, and deposits vapor of the vapor deposition material on the film 13 on the opposing cooling roller 15 to form a film. As the deposition material, not only a single metal element such as Al, Co, Cu, Ni, Ti, but also two or more kinds of metals such as Al—Zn, Cu—Zn, Fe—Co, or multi-component alloys are applied. One evaporation source 16 may be provided, or a plurality of evaporation sources 16 may be provided. Moreover, it is preferable that the both-ends edge with respect to the running direction of the film 13 forms an undeposited part so that the vapor deposition film formed on the film 13 and the cooling roller 15 are not electrically short-circuited. The undeposited width is preferably about 5 to 10 mm.
The cooling roller 15 and the auxiliary roller 18 are insulated and supported from the moving carriage plate and the end support plate 31 by the insulating support member 51 shown in FIG. 2, and both rollers are electrically separated from the ground potential as a mechanical structure. . The material of the insulating support member 51 is preferably an insulating ceramic or engineering plastic, and in particular, nylon resin, polyacetal resin, fluororesin, or the like is preferable. By using the insulating refrigerant of the present invention, the cooling roller 15 can be easily insulated simply by incorporating the insulating support member 51 without insulating the refrigerant discharge pipe 21 and the refrigerant circulator 26 on a large scale.

  Further, as shown in FIGS. 1 and 2, a DC bias power source 17 as a voltage applying means is connected between the cooling roller 15 and the auxiliary roller 18, and a DC voltage is applied between both rollers. For example, FIG. 2 shows a state where the DC bias power supply 17 is electrically connected to the cooling roller 15 via the brush 29. Although the auxiliary roller 18 is not shown, the electrical connection is the same as that of the cooling roller 15, and one polarity of the DC bias power source 17 is connected. The cooling roller 15 may be connected to the positive electrode side or the negative electrode side, but it is preferable to connect to the positive electrode side. Therefore, it is preferable to connect the auxiliary roller to the negative electrode side, and it is preferable to connect to the ground potential from the viewpoint of stability of the bias potential level, but the auxiliary roller can be used without being connected to the ground potential. When the film 13 is formed by vapor deposition material that flies from the evaporation source 16, the film 13 is electrically generated by electrostatic attraction generated between the voltage applied to the cooling roller 15 and the film formation surface that contacts the auxiliary roller 18. It is adsorbed and adhered to the surface and cooled. The DC bias power supply 17 may be either a fixed output type or a variable output type. In order to maintain the voltage applied to the cooling roller 15, it is necessary to maintain the insulation state of the cooling roller 15 itself. The coolant circulated from the coolant circulator 26 to the cooling roller 15 is generally a water-soluble antifreeze. However, since the water-soluble antifreeze is conductive, the coolant supply pipe 20 and the coolant discharge pipe 21 are not shown from the water-soluble antifreeze. Current leakage occurs to the ground side through a pipe metal joint or the like, and the voltage applied to the cooling roller 15 cannot be maintained. Therefore, in the present invention, the insulating property of the cooling roller 15 is ensured by using an insulating fluid refrigerant. The insulation of the refrigerant preferably has a volume resistivity of 1 MΩ · m or more, and if it is lower than 1 MΩ · m, a current flows to the ground through the refrigerant when a voltage is applied to the cooling roller 15, and the DC bias power supply 17 is connected. It becomes necessary to use a power supply with an excessively large current capacity. Further, the refrigerant supply pipe 20 and the refrigerant discharge pipe 21 are pipes made of an insulating material such as a rubber hose. By connecting the insulation pipe to the refrigerant circulator 26, there is a problem even if the liquid contact part of the refrigerant circulator 26 is at ground potential. The effects of the present invention can be obtained.

As for the viscosity of the refrigerant, if the viscosity is high at low temperature, the load of the motor 28 is excessive, the flow rate of liquid fed by the circulation pump 27 is reduced, and the cooling efficiency to the film is lowered. It is preferable to use it as an insulating fluid. Dimethylpolysiloxane is represented by (C ₂ H ₆ OSi) n, and those having a siloxane bond of 2000 or less exhibit oil properties, but the lower the molecular weight, the lower the viscosity, the refrigerant used in the present invention. It is preferable to use one having a kinematic viscosity of 200 m ² / s or less. This is because the film cooling is insufficient as described above, and the film is thermally deformed.

Example 1
The vapor deposition machine having the configuration shown in FIGS. 1 and 2 was used, and Barrel silicone field M-2 (a refrigerant mainly composed of dimethylpolysiloxane) manufactured by Matsumura Oil Co., Ltd. was used as the refrigerant material of the refrigerant circulator 26. The volume resistivity of the refrigerant was measured using a liquid electrode LP-05 manufactured by Kawaguchi Electric Mfg. Co., Ltd. and found to be 1 TΩ · m at a temperature of 25 ° C. The viscosity was measured using a capillary viscometer compliant with JIS K-2283 and JIS Z-8803 manufactured by Kusano Kagakusha, and the kinematic viscosity was calculated from the refrigerant density. As a result, 2.0 mm ² / s at −25 ° C., − It was 6.5 mm ² / s at 30 ° C. The refrigerant was circulated into the cooling roller 15 using this refrigerant, and the temperature of the refrigerant circulator 26 was controlled so that the surface temperature of the cooling roller 15 was −30 ° C. The temperature of the refrigerant circulator 26 is controlled by installing a temperature sensor in the refrigerant discharge pipe 21 so that the refrigerant temperature at this position becomes −30 ° C. The DC bias power supply 17 was connected using a DC power supply KX-100H (100 W) manufactured by Takasago Seisakusho, and +100 V was applied to the cooling roller 15. The film is an OPP (stretched polypropylene) film (trade name Treffan manufactured by Toray Industries, Inc.) having a thickness of 3 μm, and the aluminum is evaporated from the evaporation source 16 while being conveyed at a speed of 400 m / min. Went. As a result, the film could be formed with good quality without thermal deformation. The voltage display value of the DC bias power supply 17 was 100 V, and the current display value was 0.01 A or less. In addition, the current value of the motor 28 of the circulation pump 27 of the refrigerant circulator 26 was measured, and the load factor of the motor was confirmed by using current value / maximum allowable current value × 100 = load factor (%). In addition, since the refrigerant circulation temperature was stable at −30 ° C., it was confirmed that the refrigerant circulator 26 was able to operate well with little decrease in the refrigerant flow rate.

(Example 2)
In order to confirm the lower limit of the insulation resistance of the refrigerant, carbon powder was added to the refrigerant of Example 1. When 22 wt% of carbon black # 3030B manufactured by Mitsubishi Chemical Corporation was mixed into barrel silicone field M-2, the volume resistivity was 1 MΩ · m. This refrigerant was introduced into the refrigerant circulator 26, and an aluminum thin film was formed under the same conditions as in Example 1. As a result, although slight thermal deformation was observed in the film, the film was formed to satisfy the required quality level. The voltage display value of the DC bias power supply 17 was 100 V, and the current display value was 0.1 A. The motor load factor of the refrigerant circulator 26 and the refrigerant circulation temperature were also the same as in Example 1.

(Example 3)
A burrel silicone field M-50 manufactured by Matsumura Oil Co., Ltd. was used as the refrigerant material, and the other conditions were the same as in Example 1. The refrigerant material is the same dimethylpolysiloxane as in Example 1 and the volume resistivity is the same, but the kinematic viscosity is 50 mm ² / s at 25 ° C. and −30 ° C. as measured by the same method as in Example 1. Then, it was about 200 mm ² / s. As a result of film formation, although slight thermal deformation was observed in the film, the film formation satisfied the required quality level. The voltage display value of the DC bias power supply 17 is 100 V, and the current display value is 0.01 A or less. However, the motor load factor of the refrigerant circulator 26 is about 90%. I was concerned. Since the refrigerant circulation temperature fluctuated while hunting from −30 ° C. to about −20 ° C., it was determined that the refrigerant circulation operation was performed with the refrigerant flow rate slightly reduced.

(Comparative Example 1)
When carbon powder was added to the refrigerant of Example 1 up to 23% by weight, the volume resistance decreased to 100 kΩ · m. This refrigerant was introduced into the refrigerant circulator 26, and an aluminum thin film was formed under the same conditions as in Example 1. As a result, linear thermal deformation parallel to the film running direction was observed at the center of the film, and the required quality level was not satisfied. The voltage display value of the DC bias power supply 17 was 79V, and the current display value was 1.26A. The motor load factor of the refrigerant circulator 26 and the refrigerant circulation temperature were also the same as in Example 1.

(Comparative Example 2)
An ethylene glycol refrigerant having a concentration of 80% was used as a refrigerant material, and film formation was performed under the same conditions as in Example 1 for other conditions. This refrigerant was composed of 80% ethylene glycol, water, and a rust inhibitor, and its volume resistance value was measured by the same method as in Example 1. As a result, it was 10 Ω · m at 25 ° C. The kinematic viscosity was measured by the same method as in Example 1. As a result, it was 4 mm ² / s at 25 ° C. and about 100 mm ² / s at −30 ° C. As a result of film formation, linear thermal deformation parallel to the film running direction occurred on the entire film surface, resulting in extremely poor quality film formation. The voltage display value of the DC bias power supply 17 was 3 V and the current display value was 2.5 A. The current flowed to the upper limit of the current capacity of the DC bias power supply 17 and the voltage was greatly reduced. When the motor load factor of the refrigerant circulator 26 was measured from the motor operating current value, it increased to 50%, but there was no problem in equipment, and the refrigerant circulation temperature was constant at -30 ° C.

(Comparative Example 3)
A burrel silicone field M-100 manufactured by Matsumura Oil Co., Ltd. was used as the refrigerant material, and the other conditions were the same as in Example 1. The refrigerant material is the same dimethylpolysiloxane as in Example 1 and has the same volume resistivity. However, the kinematic viscosity was measured by the same method as in Example 1, and as a result, it was 100 mm ² / s at 25 ° C. and −30 ° C. It was about 300 mm ² / s. As a result, linear thermal deformation parallel to the film running direction was observed at the center of the film, and the required quality level was not satisfied. The voltage display value of the DC bias power supply 17 is 100 V and the current display value is 0.01 A or less, but the motor load factor of the refrigerant circulator 26 is about 98%, which is dangerous for continuous operation. there were. The refrigerant circulation temperature fluctuated while hunting from −15 ° C. to about + 10 ° C.

  The present invention is not limited to the use of a vapor deposition apparatus or a CVD film forming apparatus as a film forming apparatus, but can be applied to the entire process of transporting and cooling a film with a thin film, and is not limited to these application ranges.

DESCRIPTION OF SYMBOLS 1 Thin film forming apparatus 10 Vacuum chamber 11 Unwinding roll 12 Winding roll 13 Film 14 Conveying roller 15 Cooling roller 16 Evaporating source 17 DC bias power supply 18 Auxiliary roller 19 Partition plate 20 Refrigerant supply pipe 21 Refrigerant discharge pipe 22 Bearing 23 Seal member 24 outer cylinder 25 inner cylinder 26 refrigerant circulator 27 circulating pump 28 motor 29 brush 30 moving carriage 31 end support plate 50 vacuum pump 51 insulating support member

Claims (3)

A vacuum chamber, transport means for transporting the film inside the vacuum chamber, a cooling roller for closely cooling the film in close contact with the film, and a thin film formed on the film disposed opposite to the cooling roller Forming film forming means, an auxiliary roller for contacting the film forming surface of the film to guide the film traveling, and a voltage applying means for applying a DC voltage between the cooling roller and the auxiliary roller. In the insulating film thin film forming means, the cooling roller is held in a state electrically insulated from the vacuum chamber by a support member, and has a volume resistivity of 1 MΩ · m or more in the roller, from + 25 ° C. A method of forming a thin film, comprising circulating a liquid cooling medium having a kinematic viscosity of 200 mm ² / s or less in a range up to -30 ° C. The thin film forming method according to claim 1, wherein the cooling medium is a liquid mainly composed of a polysiloxane structure. A vacuum chamber, transport means for transporting an insulating film inside the vacuum chamber, a cooling roller in close contact with the film and circulating a cooling medium for cooling the film, and opposed to the cooling roller A direct-current voltage between a film forming means arranged to form a thin film on the film, an auxiliary roller that contacts the film forming surface of the film and guides the running of the film, and the cooling roller and the auxiliary roller In the thin film forming apparatus having a voltage applying means for applying a voltage, the volume resistivity of the cooling medium introduced into the cooling roller is 1 MΩ · m or more, and the kinematic viscosity in the range from + 25 ° C. to −30 ° C. is 200 mm. A thin film forming apparatus characterized by using a liquid of ² / s or less.

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