JP2018115383A - Manufacturing method of transparent gas barrier film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a large-area low-cost transparent gas barrier film having an excellent transparency, a gas barrier property, and adhesion by a simple vapor evaporation apparatus.SOLUTION: In a vacuum chamber 1, an unwinding part 3 continuously feeding out a plastic film 13, a winding part 4 winding the plastic film 13, a cooling drum 5 disposed between the unwinding part 3 and the winding part 4, an evaporation source 6 facing the cooling drum 5, and a magnetic pole 8 disposed inside the cooling drum 5 to generate a magnetron type magnetic field on a deposit surface of the plastic film 13 are disposed. Reactive evaporation of a metal and oxygen gas is enhanced by generating a magnetron discharge on the deposit surface of the plastic film 13 by applying an AC voltage to the cooling drum 5 from an AC power source 11.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a transparent gas barrier film. More specifically, it has high transparency and good visibility, is suitable as a packaging material, and has high gas barrier performance and strong adhesion to films, so that it can suppress deterioration and deterioration of foods and other contents. The present invention also relates to a method for producing a highly durable transparent gas barrier film having strong adhesion even after high retort treatment.

  A gas barrier film in which a metal thin film such as aluminum, aluminum oxide or silicon oxide or a metal oxide thin film is formed on a base film by a forming means such as a vacuum deposition method is used as a packaging material. As the base film, a polyester film typified by a biaxially stretched polyethylene terephthalate film is suitably used because it is excellent in heat resistance, dimensional stability, thickness uniformity, and the like.

  The food packaging material in which the gas barrier film is laminated is suitably used as a packaging material that is excellent in gas barrier performance, water resistance and moisture resistance, and excellent in boil resistance, retort resistance and environmental compatibility. Among them, those formed with a metal oxide thin film are widely used due to the transparency and the convenience of the microwave oven suitability.

  As a transparent gas barrier film, a film using a deposited film of aluminum oxide or silicon oxide is frequently used because a high light transmittance is obtained. However, when the degree of oxidation of the deposited film is increased in order to increase the transmittance, there is a problem that the gas barrier performance is deteriorated. Therefore, there is a disclosure of a technique for keeping the degree of oxidation low (Patent Document 1).

  Moreover, improvement was tried paying attention to the plasma activation technique at the time of vapor deposition toward balance of gas barrier performance and transparency (patent document 2). This is a method in which a space between a deposition source and a film surface is filled with high-density plasma by a powerful plasma generator at the time of deposition, and the deposited atoms and reactive gases are energized and activated.

  Another example of the technique using plasma is disclosed in Patent Document 3. In this technology, ion deposition is performed by implanting ions from a hollow cathode plasma source into a deposition source, and a plurality of magnetic poles rotating with the deposition drum are arranged on the back surface of the deposition drum to form a magnetic field on the surface of the film forming unit. Then, plasma is trapped.

  There is also a disclosure of a system in which a magnetron discharge is generated by applying a voltage to the film side with a fixed magnetron magnetic pole on the back side of the film on the premise of a single-wafer type substrate (Patent Document 4).

JP-A-10-226021 JP 2011-21214 A JP 2006-1224738 A Japanese Patent Laid-Open No. 2004-099883

  In the technique of Patent Document 1, the gas barrier performance is improved, but the transparency is deteriorated. To solve this problem, there is a method of changing the degree of oxidation in the film thickness direction, but a sufficient effect is not obtained.

  In the technique of Patent Document 2, although certain characteristics can be obtained, there are problems such as consuming a large amount of power to fill a large space with high-density plasma, and problems such as damage due to plasma in the chamber. . As a method of generating plasma, methods such as microwave plasma and hollow cathode plasma are used. However, the scale of equipment is large, which is reflected in the price of the vapor deposition apparatus, and further raises the cost of the product and has a problem. Equipment for hollow cathode plasma is particularly expensive.

  In the technique of Patent Document 3, since the position of the magnetic pole is fixed with respect to the cooling drum and the film pressed against the surface thereof, the plasma trapped in the magnetic field has uneven density in the film plane, There is a problem that the modified state differs depending on the location in the film plane. In addition, since the plasma for heating the deposition material is drawn onto the film surface, there is a problem that it is difficult to independently control the amount of plasma.

  In the technique of Patent Document 4, the relative position between the magnetic field and the film is fixed, the influence of the magnetic field distribution is unavoidable, and there is a problem that the modified state varies depending on the location in the film plane.

  The present invention is intended to solve such problems of the prior art, and without using a large-scale, high-output discharge, by performing efficient plasma activation with inexpensive equipment, it is possible to reduce costs and increase costs. The object is to obtain a metal oxide vapor-deposited film that is transparent and has high gas barrier performance.

In order to solve the above problems, the present invention has the following configuration.
The first invention includes a vacuum chamber, an unwinding unit that continuously feeds the plastic film, a winding unit that winds the fed plastic film, an unwinding unit, and a winding unit. A cooling drum that is disposed between the cooling film and cools in close contact with the plastic film, and is disposed opposite to the cooling drum, and a metal oxide thin film is formed on the plastic film by reactive vapor deposition of metal vapor and oxygen gas. In a winding type vacuum film forming apparatus having a film forming means, magnetic poles are arranged inside the cooling drum so that a magnetron type magnetic field is formed on the film forming surface of the plastic film. It is characterized by promoting the reactive vapor deposition of metal and oxygen gas by generating magnetron discharge on the plastic film deposition surface by applying AC voltage. A method for producing a transparent gas barrier film to.

  According to a second aspect of the present invention, a magnetron type magnetic field on the plastic film forming surface is formed in a racetrack shape in which a linear portion extends in the width direction of the cooling drum, and the linear portion reduces the width of the plastic film. It is a manufacturing method of the transparent gas barrier film as described in the above, characterized by exceeding.

  According to the present invention, oxygen gas on the plastic film deposition surface can be activated by magnetron discharge in reactive vapor deposition of metal oxide vapor deposition film, and the oxidation of the vapor deposition film can be made highly efficient, and a vapor deposition film with high density is formed. Even with a thin film thickness, high gas barrier performance can be exhibited. Moreover, the adhesive force of a plastic film and a metal oxide vapor deposition film | membrane can be improved by activating the plastic film surface by magnetron discharge.

  In addition, uniform quality of the deposited film can be obtained without being affected by the magnetic field intensity distribution of the magnetic pole held on the back surface of the film.

  A method for producing a transparent gas barrier film having good properties is obtained by using such plasma activated vapor deposition with excellent mass productivity.

It is an example of the manufacturing apparatus of the vapor deposition film of this invention. It is the figure which looked at the cooling drum of this invention from the side surface and the downward direction.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  The present invention includes a vacuum tank, an unwinding unit that continuously feeds out a plastic film, a winding unit that winds up the fed plastic film, an unwinding unit, and a winding unit. A cooling drum that is disposed between the cooling drum and cools in close contact with the plastic film, and is disposed opposite to the cooling drum, and forms a metal oxide vapor deposition film on the plastic film by reactive vapor deposition of metal vapor and oxygen gas. In a winding type vacuum film forming apparatus having a film forming means, magnetic poles are arranged inside the cooling drum so that a magnetron type magnetic field is formed on the film forming surface of the plastic film. It is characterized by promoting the reactive vapor deposition of metal and oxygen gas by generating magnetron discharge on the plastic film deposition surface by applying AC voltage. A method for producing a transparent gas barrier film to.

  As shown in FIG. 1, the metal evaporated from the vapor deposition source 6 and the oxygen gas from the oxygen gas introduction unit 7 on the plastic film unwound from the unwinding roll 3 to the cooling drum 5 are magnetron discharged from the opening 9. 10 is activated and deposited as a metal oxide. Then, it is wound up on the winding roll 4.

  The cooling drum 5 is electrically insulated from the surroundings and connected to the AC power source 11. In order to incorporate the magnetron magnetic pole 8 inside the cooling drum, a flow path 12 is formed under the surface of the cooling drum 5 and a structure is used in which a refrigerant flows, and the magnetron magnetic pole 8 is disposed behind the flow path. It is desirable to do. It is preferable that the magnetron magnetic pole electrode is kept at the same potential as the cooling drum so that no electric discharge is generated between the magnetron magnetic pole and the cooling drum back surface.

  As shown in FIG. 2, the magnetron discharge magnetic poles are arranged in a racetrack shape. The racetrack shape is a shape formed of a substantially semicircular shape that connects parallel straight portions and both ends thereof. The S / N magnetic poles are arranged in the shape of the racetrack so that one is arranged inside and the other is arranged outside, and the magnetic field lines are closed between these magnetic poles.

In the present invention, the linear portion of the race track is installed in the cooling drum in parallel with the rotation axis of the cooling drum. It is important that the magnetic lines of force between the S and N magnetic poles come out on the surface of the cooling drum, and a parallel component of the magnetic field lines is formed in a racetrack shape on the surface of the cooling drum. The strength of the magnetic field component parallel to the surface of the cooling drum on the cooling drum is preferably 10 mT (Wb / m ² ) or more in order to stably form the magnetron discharge.

  The racetrack-like discharge region needs to be in the opening 9 provided in the deposition preventing plate. That is, if a part of the racetrack-shaped discharge region does not fit in the opening 9, it is difficult for discharge to occur in the portion hidden by the deposition preventing plate, and it becomes difficult to maintain the magnetron discharge. For this purpose, it is preferable that the center line of the racetrack is about 1 to 3 cm inside the opening.

  In the present invention, by using a film having a narrower width than the straight portion of the racetrack, a uniform reforming effect can be brought about on the entire film width. In this case, the surface of the cooling drum is formed or plasma-treated at the end of the racetrack that is outside the film width on the cooling drum. In order to prevent this, it is necessary to apply tape or the like to the cooling drum. By such a method, the entire area of the film width is processed uniformly.

  In addition, a film width wider than the race track may be used on the assumption that the end of the film is not used. In this case, since the end portion is out of the discharge region and the characteristics are inferior, the characteristics are confirmed and only the effective range in the width direction is adopted for the product.

  The distance between the deposition preventing plate forming the opening and the cooling drum is preferably 0.5 to 1.5 cm. Equipment with this requirement is a relatively simple device for plasma activated vapor deposition.

  The plastic film in the present invention is preferably a polyester film mainly for use as a barrier film. Polyester is a general term for polymers having an ester bond with an acid and an alcohol, but is typically a condensation polymer of a dicarboxylic acid and a diol, such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN). It is manufactured inexpensively. Among them, PET is excellent in moldability and physical property balance, and it is preferable to use a PET film biaxially stretched by a conventional method.

  As the metal to be vapor-deposited, aluminum, silicon, zinc, magnesium, titanium, tin, etc. that can achieve both transparency and gas barrier performance can be used as metal oxides. Among them, aluminum and silicon are less likely to lose gas barrier performance even if the film is bent. desirable.

  Other gases such as nitrogen may be added to improve transparency, gas barrier performance, and bending resistance. Nitrogen has low reactivity, and the transmittance may be lowered by unreacted substances. However, when improvement in gas barrier performance and bending resistance performance is observed, nitrogen may be used within the allowable range of transmittance. Further, a rare gas such as argon or helium, hydrogen, or the like may be added to the oxygen gas in order to stabilize the magnetron discharge.

  In the present invention, the thickness of the metal oxide vapor-deposited film can be reduced as compared with other film forming methods. Although it is better for the gas barrier performance to be thick, if it is too thick, light absorption cannot be ignored and cracks are likely to occur in the film. For these reasons, the upper limit of the film thickness is preferably 30 nm in the present invention. However, since the transmittance is somewhat low at such a film thickness, it is preferably 20 nm or less, and furthermore, extremely high transmittance can be obtained at 10 nm or less.

  On the other hand, if the film thickness is thin, the gas barrier performance cannot be secured, so 3 nm is preferably set as the lower limit. If it is 5 nm or more, practical gas barrier performance can be obtained. That is, the range of 3 to 30 nm is necessary, the range of 5 to 20 nm is preferable, and further 5 to 10 nm is recommended. As a result, necessary characteristics can be obtained and vapor deposition can be performed at high speed.

In order to efficiently obtain a metal oxide deposited film by reactive deposition while maintaining a stable magnetron discharge, it is desirable that the pressure of the oxygen gas be 3 × 10 ^{−2 to} 5 × 10 ⁻¹ Pa. If this pressure is low, the reaction during vapor deposition is difficult to proceed, and since the discharge voltage is high and abnormal discharge is likely to occur, it is preferable to set the lower limit to 3 × 10 ⁻² Pa. If the pressure is increased, the reaction with oxygen gas is promoted and the discharge voltage is reduced. However, if the pressure is too high, the load of the exhaust by the vacuum pump increases, and the surface of the plastic film is caused by scattered particles (splash) from the molten metal of the evaporation source. Therefore, it is preferable to set the upper limit to 5 × 10 ⁻¹ Pa.

  In the present invention, discharge is generated by applying an AC voltage to the cooling drum, but the frequency may be in a range where the discharge can be stably maintained. The RF frequency of 13.56 MHz is convenient in terms of maintaining a strong discharge, but it is necessary to consider matching and leakage. A high frequency of 5 kHz to 1 MHz is relatively easy to use, but since it tends to be difficult to discharge on the low frequency side, it may be determined while observing the discharge state.

The intensity of the magnetron discharge has a great influence on the reaction state of the deposited film obtained. The higher the intensity of the discharge, the higher the degree of reaction, but the capacity of the power source is also limited, and abnormal discharge is likely to occur, so the film speed V (m / s), the length of the racetrack in the film width direction of the discharge area When the discharge area LV (m ² / s) per unit time is defined by the length L (m), the discharge power amount (P / LV) per unit area with respect to the input power P (kW) is It is preferable that it is 9.0 (kWs / m < ² >) or less. When the amount of discharge power per unit area is low, activation by plasma during vapor deposition is not performed, and thus it is preferably 0.4 (kWs / m ² ) or more.

  In the magnetron discharge according to the present invention, the discharge voltage is lowered and the discharge region is limited in the region of the racetrack-shaped magnetic field, so that discharge at an unnecessary place can be avoided. This eliminates the need for a shield plate as a discharge prevention measure for other parts of the cooling drum. Further, the discharge location can be fixed on the film-forming surface of the plastic film, and the activation effect can be maximized while minimizing the generation region of the magnetron discharge.

  The magnetic pole of the magnetron is fixed in the cooling drum. Meanwhile, the surface of the cooling drum rotates to feed the plastic film. By this movement, the plastic film passes through the front of the magnetic pole to follow a uniform history, and a uniform plasma processing effect and film quality are obtained. The structure of the apparatus is simple, and uniform activated vapor deposition can be performed over a large area.

  The vapor deposition film produced by the production method of the present invention has high gas barrier performance and durability, and is preferably used as a packaging material for high retort. For this purpose, it is effective to perform a protective coating after vapor deposition. As an example, it may be possible to form a protective film formed by applying a liquid comprising a metal alkoxide and polyvinyl alcohol followed by heat curing. On top of that, a heat sealable film such as a nylon film and polypropylene can be laminated using an adhesive, so that it can be used as an excellent packaging material for high retort.

  According to the present invention, such a high-quality transparent gas barrier film can be produced with high productivity by a relatively simple apparatus.

  Hereinafter, the present invention will be described in more detail with reference to examples. In addition, the physical property in an Example and a comparative example was measured as follows.

(1) Total light transmittance The total light transmittance (%) of the transparent gas barrier film produced by the vapor deposition method of the present invention was measured with a haze meter NDH2000 manufactured by Nippon Denshoku Industries Co., Ltd. A decrease was within 5.0% with respect to the total light transmittance of the polyester film before vapor deposition. Since the total light transmittance before vapor deposition of the polyester film used in this study was 89.0%, 84.0% or more was regarded as acceptable.

(2) Oxygen permeability A sample cut to a width of 100 × 100 mm was prepared from the transparent gas barrier film produced by the vapor deposition method of the present invention, and the oxygen permeability (cc / (m ² day · atm)) was measured according to JISK7126-2. According to (Established August 20, 2006), measurement was performed under the conditions of 23 ° C. and 0% RH using an oxygen permeability measuring device OX-TRAN 2/20 manufactured by Modern Control. The average value of 3 samples was obtained. An oxygen transmission rate of ² cc / (m ² day · atm) or less was set as an acceptable range.

(3) Water vapor transmission rate A sample cut to a width of 100 × 100 mm was prepared from the transparent gas barrier film produced by the vapor deposition method of the present invention, and the water vapor transmission rate (g / (m ² day)) was set to JISK7129B (established 2008). (March 20), using a water vapor transmission rate measuring device Permatran-W3 / 30 manufactured by Modern Control Co., under the conditions of 40 ° C. and 90% RH. The average value of 3 samples was obtained. A water vapor transmission rate of 2 g / (m ² day) or less was set as an acceptable range.

(4) Low-speed wet adhesion strength 20 parts by weight of AD-503 type adhesive for dry lamination manufactured by Toyo Morton Co., Ltd. 1 part by weight of curing agent CAT-10 type manufactured by Toyo Morton Co., Ltd. and 20 parts by weight of ethyl acetate are mixed. Then, the mixture was stirred for 10 minutes to prepare a dry laminate adhesive solution having a solid content of 19% by weight. Next, the adhesive solution was applied to the vapor deposition surface of the transparent gas barrier film by a bar coating method, and dried at 80 ° C. for 45 seconds to form an adhesive layer having a thickness of 3.5 μm. An unstretched polypropylene (CPP) film “Treffan” (registered trademark) ZK100 (thickness 60 μm) manufactured by Toray Film Processing Co., Ltd. is stacked on the adhesive layer surface, and “Lami Packer” (LPA330) manufactured by Fuji Tech Co., Ltd. is used. The heat roll was heated to 40 ° C. and bonded. This laminate film was aged in an oven heated to 40 ° C. for 2 days to cure the adhesive.

  A cut sample was prepared by cutting the film into a 15 cm square size from the laminate film. Two cut samples were stacked so that the CPP surfaces face each other, and a heat sealer was used to heat-seal the 3 mm end portions of 10 mm, thereby producing a 15 cm square package. After adding 100 cc of tap water, the heat seal part was crimped and sealed at 140 ° C. for 2 seconds.

  Next, the package was retorted at a temperature of 135 ° C. for 40 minutes using an autoclave (SR-24 type) manufactured by Tommy Seiko Co., Ltd.

  After the retort treatment, it was kept at 40 ° C. for about 16 hours and dried. Then, the package is cut into a width of 15 mm and a length of 150 mm to create a cut sample, and “Tensilon” (PTM50 type) manufactured by Orientec Co., Ltd. is used as an interface between the transparent gas barrier film and the CPP film. While applying water to the interface with a cotton swab, peeling was performed at a pulling rate of 300 mm / min by a 180 ° peel method, and the strength was measured. These measurements were performed using two different cut samples, and the average value obtained was defined as the low-speed wet adhesion strength (N / 15 mm) after retorting. 1.5 N / 15 mm or more was regarded as acceptable.

Example 1
A magnetron cathode magnetic pole having a racetrack length of 18 cm and a width of 5 cm was incorporated in the cooling drum. The shape of the opening was 20 cm long and 8 cm wide. The cooling drum and the adhesion preventing plate at the opening were spaced 1 cm apart.

A biaxially stretched polyethylene terephthalate film for packaging (“Lumirror” (registered trademark) P60, thickness 12 μm, width 210 mm) manufactured by Toray Industries, Inc.) is set as a polyester film in the film unwinding portion, and an ultimate pressure of 8 × A vacuum was drawn to 10 ⁻³ Pa.

  As the evaporation source, resistance heating type boats were arranged at equal intervals, and aluminum wires were sent onto the boat to evaporate. Oxygen gas was flowed at a flow rate of 0.54 L / min for reactive deposition. The film was run at a speed of 1 m / s, and a high frequency of 50 kHz was applied to the cooling drum from an AC power source with a power of 0.41 kW. A racetrack-shaped magnetron discharge was generated on the film deposition surface on the cooling drum in the opening.

  The aluminum oxide film thickness was adjusted to 6 nm by adjusting the supply rate of the aluminum wire to the resistance-heated boat in this state. The temperature of the cooling drum at this time was −4 ° C.

(Example 2)
In the same manner as in Example 1, the high frequency power applied to the cooling drum was set to 0.25 kW.

(Example 3)
In the same manner as in Example 1, the high frequency power applied to the cooling drum was set to 0.11 kW.

(Comparative Example 1)
In the same method as in Example 1, no high frequency was applied to the cooling drum. The adhesion was significantly reduced and other properties were also out of the non-defective level.

  Table 1 shows the production conditions of Examples and Comparative Examples and the performance of the produced transparent gas barrier films.

DESCRIPTION OF SYMBOLS 1 Vacuum chamber 2 Vacuum pump 3 Unwinding roll 4 Winding roll 5 Cooling drum 6 Deposition source 7 Oxygen gas introduction part 8 Magnetron magnetic pole 9 Opening part 10 Magnetron discharge 11 AC power supply 12 Flow path 13 through which a refrigerant flows Plastic film 14 Plasma is formed Race track 15

Claims (2)

  Arranged between the unwinding unit and the unwinding unit, the unwinding unit for continuously unwinding the plastic film, the unwinding unit for unwinding the unloaded plastic film, and the unwinding unit disposed in the vacuum chamber A cooling drum that is in close contact with the plastic film and is cooled, and a film forming means that is disposed opposite to the cooling drum and forms a metal oxide vapor deposition film on the plastic film by reactive vapor deposition of metal vapor and oxygen gas. In the winding type vacuum film-forming apparatus equipped with a magnetic pole is arranged inside the cooling drum so that a magnetron type magnetic field is formed on the film-forming surface of the plastic film, and an AC voltage is applied to the cooling drum. By generating a magnetron discharge on the film-forming surface of the plastic film, the reactive vapor deposition of metal and oxygen gas is promoted. Method of manufacturing a gas barrier film. The magnetron type magnetic field on the film-forming surface of the plastic film is formed in a racetrack shape in which a linear portion extends in the width direction of the cooling drum, and the linear portion exceeds the width of the plastic film. The manufacturing method of the transparent gas barrier film of Claim 1.