JPH05339704A - Method for producing transparent gas barrier film - Google Patents

Abstract

(57) [Summary] [Purpose] The object is to stably produce a film having high transparency and excellent gas barrier properties. [Structure] A polymer resin film substrate is continuously run,
In a reactive vapor deposition method of continuously forming an aluminum oxide film on the polymer resin film substrate by reacting aluminum vapor and oxygen on the polymer resin film substrate, on an evaporation source for evaporating aluminum vapor. The reaction-deposited portion is provided by providing a reaction-deposited portion surrounded by the deposition preventive plate having the opening and the running film, and introducing oxygen into the space between the polymer resin film and the deposition-inhibited plate in which aluminum vapor does not fly. 2. A method for producing a transparent gas barrier film, which comprises providing a pressure distribution of oxygen in the film running direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a transparent gas barrier film having excellent oxygen and water vapor barrier properties.

[0002]

2. Description of the Related Art In order to preserve foods and drugs for a long period of time,
It is necessary to carry out packaging having excellent so-called gas barrier properties, which has an effect of blocking the invasion of oxygen and water vapor from the outside air that promotes decay and deterioration. In recent years, there has been an increasing tendency in particular for film packaging materials having excellent gas barrier properties, which are used for this purpose, to be required to have transparency so that the state of the contents can be confirmed.

It is well known in the art that a metal oxide formed on a polymer resin film substrate has excellent gas barrier properties and transparency. Among these, particularly those having silicon oxide formed on a polymer resin film base are disclosed in JP-B-53-12953, and those having aluminum oxide formed on a polymer resin film are JP-B-62-17.
It is known from Japanese Patent No. 9935.

By the way, the silicon oxide thin film is, for example, German LEY.
B.T. G. Krug et al. Are Barrier P
ack Conference (London, Ma
y21 and 22, 1990) and the magazine "Convertec" 1990.6 30-36.
As shown in the page (by Keisuke Kaiho), 50n is required to secure high gas barrier properties (oxygen permeability ² cc / m ² · day or less, water vapor permeability 2 g / m ² · day or less).
A film thickness of about m is required. In addition, a complete oxide film of Si
Since the composition of O ₂ does not exhibit the gas barrier property, a thin film having a composition of oxygen deficiency, that is, a composition of SiO _x (X <2.0) is formed. So it's transparent,
Absorption on the short wavelength side becomes large and the vapor deposition film has a yellow coloration, and when food is put inside, it is difficult to understand the state of alteration, or it seems that alteration is occurring even if it is not altered. There is. In addition, when a thin base film is used due to its large thickness, curling is likely to occur, which causes poor handling properties, and if handled roughly, cracks will occur in the vapor deposition film and gas barrier properties will deteriorate. is there.

On the other hand, the aluminum oxide film is colorless and transparent,
A gas barrier property can be exhibited to some extent. However, in order to obtain a transparent aluminum oxide film, it is necessary to increase the amount of oxygen to react with the amount of evaporation of aluminum to completely oxidize aluminum. However, it was extremely difficult to control them by the conventional oxygen introduction method. This improved method is disclosed in Japanese Examined Patent Publication No. 4-20383, which limits the amount of oxygen introduced with respect to the amount of evaporated aluminum, but the magazine "Japan Food Science" 1990.12 pages 58 to 63 (written by Hideo Watanabe). It is impossible to develop a gas barrier property comparable to that of a silicon oxide thin film as described in (4), and it was necessary to further study the manufacturing method.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to stably produce a transparent gas barrier film made of an aluminum oxide film which solves the above problems.
That is, the present invention aims to stably produce a film having particularly high transparency and excellent gas barrier properties.

[0007]

SUMMARY OF THE INVENTION The present invention is directed to a polymer resin film substrate by continuously running the polymer resin film substrate and reacting aluminum vapor and oxygen on the polymer resin film substrate. In a reactive vapor deposition method for continuously forming an aluminum oxide film on a material, a deposition layer having an opening is provided on a vaporization source for vaporizing aluminum vapor, and a reactive vapor deposition portion surrounded by the traveling film is provided, and A method for producing a transparent gas barrier film, characterized in that a pressure distribution of oxygen is provided in a film running direction of the reaction vapor deposition portion by introducing oxygen into a space where aluminum vapor does not fly between the molecular resin film and the deposition preventive plate. is there.

The constituent features of the present invention will be described below.
In order to continuously form a thin film on a polymer resin film substrate, a method is generally used in which the film is unwound from a roll-shaped film substrate onto a cooling drum for vapor deposition, and then wound into a roll after vapor deposition. ..

The method for forming the aluminum oxide film in the present invention is by reactive evaporation. According to this method, the aluminum oxide film can be formed by evaporating aluminum metal and reacting it with oxygen on the polymer resin film substrate. Oxygen may be used alone or may be diluted with an inert gas. The evaporation source for evaporating aluminum includes, but is not particularly limited to, a boat type of resistance heating system, a crucible type of radiation or high frequency heating, and a system of electron beam heating.

The prior art and the present invention will be described below with reference to the drawings. FIG. 2 shows a general schematic diagram of the above-mentioned prior art reactive deposition apparatus. The film 9 is unwound from the unwinding roll 1, is supplied to the cooling drum 3, and aluminum vapor evaporated from the evaporation source 5 in the lower part of the drum reacts with oxygen introduced from the oxygen introduction path 7 to form an aluminum oxide thin film. After that, it is wound around the winding roll 2.
In such a vapor deposition apparatus, the upper film transport section and the lower vapor deposition section are separated from each other by the partition wall 4, and the lower section is exhausted by an exhaust pump having a higher performance than the exhaust pump of the upper section, and is generally kept at a low pressure suitable for vapor deposition. Target. The reactive vapor deposition is performed in the area surrounded by the deposition preventive plate 6. Oxygen is introduced through the inlet 8 near the film. However, the reactive vapor deposition apparatus having the structure shown in FIG. 2 has a problem that the introduced oxygen tends to flow directly toward the evaporation source 5 and the surface of the molten aluminum of the evaporation source is oxidized to reduce the evaporation rate.

FIG. 1 shows a schematic diagram of the reactive vapor deposition apparatus of the present invention. However, FIG. 1 shows an example of the present invention, and the present invention is not restricted or limited to this shape. In the method for forming aluminum oxide according to the present invention, the vapor deposition source 5 is provided with a reaction vapor deposition portion surrounded by a deposition preventing plate 11 having an opening 12 and a polymer resin film substrate 9 on a cooling drum to introduce oxygen. Oxygen introduced from the path 7 is introduced from the inlet 8 at a position where aluminum vapor does not directly fly in the space between the deposition preventive plate and the film substrate, and the oxygen pressure distribution (in this case, from left to right) in the reactive vapor deposition section. Oxygen pressure is reduced) is a basic requirement. Oxygen may be introduced from either the unwinding side or the winding side of the film, or both.

By adopting such a structure, while the oxygen introduced from the inlet 8 is diffused in the direction of the opening 12, it is made uniform in the width direction of the cooling drum, and the effect of reducing vapor deposition unevenness in the film width direction is obtained. Is also accepted. In addition, since oxygen does not diffuse directly toward the evaporation source but diffuses toward the evaporation source only through the opening, the efficiency of consumed oxygen for reactive vapor deposition increases, and the surface of the molten aluminum surface of the evaporation source is oxidized. Is less likely to occur, and the problem of reduced deposition rate can be solved. For this purpose, it is important to make the clearance between the cooling drum and the deposition preventive plate as small as possible so that oxygen does not flow in the direction other than the opening. Due to these effects, a vapor deposition film that is uniform in the width and length directions of the film can be obtained. While these favorable side effects are observed, the most important point of the present invention is that the reaction between aluminum vapor and oxygen can be precisely controlled. It is necessary that an incompletely oxidized layer containing at least one layer of metallic aluminum is present in the aluminum oxide film according to the present invention, and the principle by which the layer structure of the aluminum oxide thin film can be easily achieved by the present invention is as follows. It will be described with reference to the drawings.

FIG. 3 shows a schematic view of the reactive vapor deposition section when oxygen is introduced from the film unwinding side as shown in FIG. Considering the positions of the reactive vapor deposition units 14, 15, and 16, vapor deposition is performed at the position 14 at the beginning of vapor deposition and at the position 16 at the end of vapor deposition. Since oxygen is consumed from the side closer to the inlet 8, the oxygen pressure gradually decreases in the order of 14, 15, 16
The distribution is as shown in FIG. On the other hand, as is generally known, the aluminum vapor strength is proportional to cos ⁿ θ (n is generally a value of 2 to 4) because the vapor strength in the direction of the angle θ from the normal direction of the evaporation source is proportional to cos ⁿ θ. Similarly, the distribution shown in FIG. 4 is taken. Oxygen partial pressure was applied to the beam intensities of aluminum vapor in the vicinity of 14 and 16 such that aluminum could be completely oxidized, but to the beam intensities of aluminum vapor in the vicinity of 15, aluminum could not be sufficiently oxidized. In this case, in the vicinity of 14 and 16, that is, in the initial stage of vapor deposition and at the end of vapor deposition, a fully-oxidized layer fully supplied with oxygen is formed, and in the central part of 15, an incompletely-oxidized layer with insufficient oxygen is formed. When the oxygen pressure does not change depending on the location, the incomplete oxide layer is formed at the center of 15, but in the case of FIGS. 3 and 4, the incomplete oxide layer is formed at the position shifted to the 16 side, that is, the surface side. When unwinding and introducing oxygen from both sides of winding as shown in FIGS. 5 and 6, oxygen is insufficient in the central portion, and an incompletely oxidized layer is formed in the central portion. When oxygen is introduced from the winding side contrary to FIGS. 3 and 4, it can be easily inferred that an incompletely oxidized layer is formed at a position close to the film interface.

In the method of giving a uniform oxygen partial pressure to the entire space including the space below the deposition-inhibitory plate, that is, in the case where the oxygen atmosphere is uniformly introduced into the upper and lower portions of the deposition-inhibitory plate, the structure of the present invention is adopted. It is extremely difficult to obtain the aluminum oxide film that it has. The reason for this is as follows. That is, as described above, when the oxygen partial pressure of the vapor deposition portion on the deposition preventive plate is made to be a target value, the oxygen partial pressure of the evaporation source portion simultaneously rises, and an oxide film is formed on the surface of the aluminum melt of the evaporation source. It is easy to be done. When an oxide film is formed on the surface of the aluminum melt, the evaporation rate of aluminum sharply decreases. Therefore, the aluminum vapor strength is reduced as a whole, and the degree of oxidation of the formed film is increased. At the same time, a decrease in the evaporation rate of aluminum causes a decrease in oxygen consumed in the formation of an aluminum oxide film and an increase in the oxygen partial pressure. As a result, it becomes difficult to stably form an aluminum oxide film having a layer containing an aluminum metal component inside.

In any case, in order to obtain the film of the present invention, it is essential to introduce an oxygen atmosphere near the vapor deposition portion (near the polymer resin film substrate). Further, by providing a reactive vapor deposition section surrounding the area where oxygen is consumed, the relationship between the above-mentioned beam intensity of aluminum vapor and oxygen partial pressure can be accurately controlled, oxygen can be used efficiently, and an exhaust pump can be used more than necessary. It is also important to avoid overloading. According to the constitution of the present invention, the efficiency of consumed oxygen for reactive vapor deposition is preferably 80% or more. If it is less than 80%, the molten aluminum surface of the evaporation source is likely to be oxidized. The efficiency consumed for reactive vapor deposition of oxygen is defined by the following method. That is, assuming that the pressure when oxygen is introduced without evaporating aluminum is P ₀ and the pressure when vapor deposition is P, (P ₀ −P) is the pressure consumed for reactive vapor deposition. Therefore, it is defined as (P ₀ −P) / P ₀ . If the structure has a large opening area and the introduced oxygen easily flows out directly to the evaporation source, the efficiency is lowered and it becomes difficult to produce a film having excellent gas barrier properties.

The polymer resin film is not particularly limited, but typical ones include polyolefins such as polyethylene and polypropylene, polyethylene terephthalate, polybutylene terephthalate and polyethylene.
Polyesters such as 2,6-naphthalate, polyamides such as nylon 6 and nylon 12, polyvinyl chloride,
Polyvinylidene chloride, ethylene vinyl acetate copolymer, polystyrene, polycarbonate, polyacrylonitrile, polysulfone, polyphenylene oxide, polyphenylene sulfide, aromatic polyamide, polyimide, polyamideimide, cellulose, cellulose acetate and the like, and these copolymers, Examples thereof include copolymers with other organic substances. From the viewpoint of transparency and gas barrier properties, polyesters such as polyethylene terephthalate, polyolefins such as polyethylene and polypropylene are preferable, and polyethylene terephthalate type is more preferable.

In the case of a thermoplastic resin, these polymer resin films may be unstretched, uniaxially stretched or biaxially stretched, but are biaxially stretched from the viewpoint of dimensional stability, mechanical properties and gas barrier stability. Those that are preferred. In addition, known additives such as antistatic agents, antioxidants, lubricants, anticolorants, ultraviolet absorbers, plasticizers, and colorants are added to the polymer resin film if they do not cause food hygiene problems. May be.

The polymer resin film used in the present invention is preferably transparent and has a light transmittance of preferably 40%.
Or more, more preferably 60% or more, and further preferably 8
It is 0% or more. Prior to vapor deposition, a known surface treatment such as corona discharge treatment, glow discharge treatment, or anchor coating treatment by coating may be performed on the film.

Further, it is desirable that the surface of the polymer resin film used in the present invention for forming the aluminum oxide film is smooth. The center line average roughness is preferably 0.5 μm or less, more preferably 0.2 μm or less, still more preferably 0.05 μm or less. The reason for this is that if there are large protrusions on the film surface, the gas barrier vapor deposition film will not be formed uniformly.

The thickness of the polymer resin film is not particularly limited, but is 5 μm to 50 which is suitable as a packaging material.
The range of 0 μm is preferable.

In the transparent gas barrier film according to the present invention, the total thickness of the aluminum oxide film formed on the polymer resin film is preferably 6 nm or more. If the total film thickness is less than 6 nm, the gas barrier performance will be insufficient.

The total thickness of the aluminum oxide film is 50.
It is preferably less than nm. The reason for this is that, as described above with respect to the silicon oxide vapor-deposited film, if the total film thickness is large, curling is likely to occur, which may cause a problem that the gas barrier property is sharply lowered during processing. From the viewpoint of productivity, the total film thickness is preferably small, and more preferably the total film thickness is less than 30 nm.

In the transparent gas barrier film produced by the present invention, it is important that at least one incompletely oxidized layer containing the metal component of aluminum is present only inside the aluminum oxide film. It is difficult to obtain an excellent gas barrier property if the incompletely oxidized layer containing the metal component does not exist inside the aluminum oxide film and the entire aluminum oxide film is composed of the complete oxide film.
On the other hand, when the entire aluminum oxide film is composed of an incomplete oxide film and the metal component of aluminum is recognized, the light transmittance tends to be low, which is not preferable.

Here, the presence or absence of the metal component of aluminum in the aluminum oxide film is determined by the Al2p spectrum obtained by X-ray photoelectron spectroscopy (hereinafter sometimes referred to as XPS) analysis, which is an analytical method with extremely high surface sensitivity. Can be determined. That is, the peak due to the trivalence of oxidized aluminum in the spectrum (Al (III))
In addition, when it has an Al (0) peak indicating the presence of a metal component, it can be seen that the metal component of aluminum is contained. Further, in order to confirm that the aluminum metal component is contained only in the aluminum oxide film, the XPS analysis is performed not only from the surface of the aluminum oxide film, but also the aluminum oxide film is gradually ion-etched from the surface. However, it is necessary to perform XPS analysis and follow the change in the Al2p spectrum (hereinafter referred to as depth profile) along the depth direction of the aluminum oxide film.

[0025]

[Characteristic Measuring Method and Effect Evaluation Method] The characteristic values of the present invention are determined by the following measuring methods.

(1) Total film thickness The film thickness was determined by the peak intensity of aluminum by fluorescent X-ray spectroscopy, which was calibrated by observation of a cross section with a transmission electron microscope. X-ray fluorescence spectroscopy was performed with SEA2001 manufactured by Seiko Denshi. Some of the samples subjected to the fluorescent X-ray spectroscopy were taken with a transmission electron microscope (JEM-1 manufactured by JEOL Ltd.).
The cross section of the vapor-deposited film was cut out and observed by the ultra-thin section method with 200 EX), and it was confirmed that the aluminum peak intensity of the fluorescent X-ray and the actual film thickness are in a good proportional relationship.

(2) Confirmation of the presence of aluminum metal Using an X-ray photoelectron spectrometer (SSX-100 manufactured by SSI), an X-ray source AlKα, an X-ray output of 10 kV-10 mA, and an escape angle of photoelectrons with respect to a normal line of the sample surface. Was measured at an angle of 55 degrees. Etching for depth profile measurement was performed using Ar ions at an acceleration voltage of 3 kV and a sample current of 10.3 μA.

(3) Water vapor transmission rate Water vapor transmission rate measuring device (W82, manufactured by Honeywell Co., Ltd.)
5) was used under the conditions of 40 ° C. and 100% RH.

(4) Oxygen Permeability According to ASTM D-3985, the oxygen permeability was measured under the conditions of 20 ° C. and 0% RH using an oxygen permeability measuring device (Modern Control Co., OX-TRAN100).

(5) Specific light transmittance Spectrophotometer (Hitachi, Ltd., autograph spectrophotometer 323)
Type), the ratio of the light transmittance of the polymer resin film after the aluminum oxide film was provided to the light transmittance of the polymer resin film substrate at a wavelength of 550 nm was defined as the specific light transmittance.

[0031]

EXAMPLES The present invention will be described with reference to examples.

Examples 1 to 3 Samples were prepared with the constitution of the reactive vapor deposition portion shown in FIG. The evaporation source was an electron beam heating evaporation source, and 99.99% aluminum metal was loaded into an alumina crucible for vapor deposition. The film is polyethylene terephthalate (hereinafter referred to as PET) film "Lumirror" P manufactured by Toray Industries, Inc.
60 (12 μm) was used. The film is fed from the unwinding roll in the form of a roll onto the cooling drum, and vapor deposition is performed directly above the evaporation source. As the oxygen atmosphere, 100% oxygen was introduced from the unwinding side. The cooling drum was cooled to about 20 ° C. with cold water.
The vapor deposition procedure is as follows. The film and aluminum for vapor deposition are set in a continuous vapor deposition machine, and vacuum exhaust is performed. When the ultimate pressure becomes 2 × 10 ⁻⁵ Torr or less, the film is made to travel, and electric power is applied to the electron beam evaporation source to start vapor deposition of aluminum. An in-line light transmittance meter and a resistivity meter are used to adjust the electric power of the evaporation source so as to obtain a target evaporation rate, and then oxygen gas is introduced through a mass flow controller. Set the film traveling speed to a low speed (for example, 1 m / min) and confirm that the light transmittance monitored in-line increases as oxygen is introduced. Adjust. Increase the film running speed to obtain the desired film thickness and take a sample. The pressure during vapor deposition is stable at 5 × 10 ⁻⁵ Torr, and the pressure when evaporation of aluminum is stopped is 4 × 10 5.
It became ^-4 Torr. The consumption efficiency is 88%.

Samples prepared in this way and having different vapor deposition film thicknesses were prepared as Examples 1-3. In all of these samples, it was confirmed by XPS analysis of the depth profile that a complete oxide film was formed on the surface and the PET film interface, and that an incomplete oxide layer containing a metal was present near the surface.

Comparative Examples 1 to 3 By the reactive vapor deposition apparatus according to the above-mentioned conventional technique, vapor deposition was performed with the same power and oxygen flow rate applied to the evaporation source.
The pressure during vapor deposition increased from 9 × 10 ⁻⁵ Torr at the beginning of vapor deposition to 1.3 × 10 ⁻⁴ Torr at the latter half of vapor deposition. The pressure when evaporation of aluminum is stopped is 4 × 10 ^-4 To
rr, and the consumption efficiency dropped from 78% to 68%.
Samples sampled at three points at the beginning and middle of vapor deposition and at the end of vapor deposition were set as Comparative Examples 1 to 3. All samples are X
No incomplete oxide layer was observed in the depth profile of PS analysis.

Examples 4 to 6 With the constitution of the reactive vapor deposition portion shown in FIG. 5, vapor deposition was carried out in the same amount as in Examples 1 to 3 with the same amount of oxygen from both the unwinding side and the winding side. .. The pressure during vapor deposition is 7 × 10 ^-5
It was stable at Torr, and again it was 4 × 10 ⁻⁴ Torr when the vapor deposition was stopped. The efficiency is 83%.
Samples with different film thickness were set as Examples 4 to 6. XP
It was confirmed by S analysis that an incompletely oxidized layer containing a metal was present in almost the center of the film.

The results are summarized in Table 1 together with the original PET film.

[0037]

[Table 1]

[0038]

According to the present invention, an aluminum oxide film having an incomplete oxide layer containing aluminum metal in the aluminum oxide film can be stably manufactured.

The transparent gas barrier film produced by the present invention is characterized by high light transmittance and high gas barrier performance against oxygen and water vapor. In addition, there is no yellowish coloring, and it has practically sufficient processing suitability.

The transparent gas barrier film produced according to the present invention can be widely used as a packaging material for foods and chemicals that require long-term storage. It can also be used in a packaging form such as a so-called retort pouch or standing pouch in which food can be sterilized by a retort or a boil and stored for a long time. Furthermore, since the light transmittance is high, it is possible to meet the demand for checking the state of the contents. In addition, since the microwave transmittance is high, it is possible to meet the demand that the contents are cooked as they are in a microwave oven in the packaged state. The transparent gas barrier film can be used alone, but may be further printed, coated with a protective layer on the aluminum oxide film, laminated with another film, or a combination thereof. It can also be processed further and used.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a reactive vapor deposition device according to the present invention.

FIG. 2 is a schematic view showing an example of a reactive vapor deposition device according to the prior art.

FIG. 3 is a schematic view showing an example of a reactive vapor deposition portion of a reactive vapor deposition device according to the present invention.

FIG. 4 shows the relationship between aluminum vapor strength and oxygen partial pressure in the case of FIG.

FIG. 5 is a schematic view showing an example of a reactive vapor deposition portion of the reactive vapor deposition device according to the present invention, similar to FIG.

FIG. 6 shows the relationship between aluminum vapor strength and oxygen partial pressure in the case of FIG.

[Explanation of symbols]

 1: Unwinding roll 2: Winding roll 3: Cooling drum 4: Partition wall 5: Evaporation source 6: Deposition plate 7: Oxygen introduction path 8: Oxygen introduction port 9: Film 10: Cooling drum rotation direction 11: Deposition plate 12: Opening 13: Aluminum vapor 14: Vapor deposition position 15: Same as above 16: Same as above 17: Oxygen introducing port 18: Oxygen introducing path

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display area C08J 7/04 P C23C 14/56 8520-4K // B32B 9/00 A 7258-4F

Claims (2)

[Claims] 1. A polymer resin film substrate is continuously run, and aluminum vapor and oxygen are reacted on the polymer resin film substrate to continuously form an aluminum oxide film on the polymer resin film substrate. In the reactive vapor deposition method of forming a film, a deposition layer having an opening and a reactive deposition portion surrounded by the running film are provided on an evaporation source for evaporating aluminum vapor, and a space between the polymer resin film and the deposition plate is provided. 2. A method for producing a transparent gas barrier film, comprising providing oxygen pressure distribution in the film running direction of the reaction vapor deposition portion by introducing oxygen into a space where aluminum vapor does not fly. 2. The method for producing a transparent gas barrier film according to claim 1, wherein the efficiency of the introduced oxygen for reactive vapor deposition is 80% or more.