JPH05338072A - Transparent gas barrier film - Google Patents

Abstract

PURPOSE:To improve a transparency, gas barrier properties, and heating properties by microwave oven by a method wherein the whole film thickness and aluminum metal component content of an aluminum oxide film formed on a polymer resin film substrate are respectively specified, and an incompletely oxidized layer is provided in this film. CONSTITUTION:An aluminum oxide film is formed on at least one surface of a polymer resin film. At this time, the whole film thickness of the aluminum oxide film is determined to be not less than 6nm. At least one incompletely oxidized film layer incorporating an aluminum metal component is provided only in the aluminum oxide film. The content of the aluminum metal component in the whole aluminum oxide film is determined to be within a range of 0. 5-10%.nm. On the other hand, the film is set to have a specific ray transmittance of 90% or more in a wavelength of 550nm, an oxygen transmittance of 2cc/m<2>.day or less, a water vapor transmittance of 2 g/m<2>.day or less. At the time of production, the polymer resin film 8 is supplied to a cooling drum 7 disposed above a vapor source 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent gas barrier film excellent in 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, in particular, those in which silicon oxide is formed on a polymer resin film are disclosed in Japanese Examined Patent Publication Sho 53.
Japanese Patent Publication No. 12953/1987 discloses that aluminum oxide is formed on a polymer resin film substrate.
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, the magazine “Japan Food Science” 1990.12
As described on pages 58 to 63 (written by Hideo Watanabe), it was impossible to develop a gas barrier property comparable to that of a silicon oxide thin film. As a similar application of an aluminum oxide film, Japanese Patent Application Laid-Open No. 62-220330 discloses a polymer for an incomplete aluminum oxide film containing 1 to 15% by weight of a metal component of aluminum as a packaging material for electronic materials. A film formed on a resin film substrate and having antistatic property and gas barrier property is disclosed. However, it is described that the light transmittance is considerably reduced by the presence of at least 1% by weight of aluminum metal in the entire film, and there is a problem in transparency. Further, since the film has antistatic property (that is, conductivity), it has a low microwave transmittance and cannot be heated when used as a packaging material and heated in a microwave oven while packaging the contents. was there.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems. That is, an object of the present invention is to provide a film having particularly high transparency and excellent gas barrier properties, and in which the drawbacks such as coloring and microwave oven heating that the conventional transparent gas barrier films have are eliminated.

[0007]

The present invention is a film in which an aluminum oxide film is formed on at least one side of a polymer resin film substrate, and the total thickness of the aluminum oxide film is 6 nm or more, In addition, at least one incompletely oxidized layer containing a metal component of aluminum exists only inside the aluminum oxide film, and the content of the aluminum metal component in the entire aluminum oxide film is 0.5.
It is a transparent gas barrier film characterized by being in the range of% .nm to 10% .nm.

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, the surface of the polymer resin film used in the present invention for forming the aluminum oxide film is preferably 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 500 μm as a packaging material.
Is preferred.

In the transparent gas barrier film of the present invention, the total thickness of the aluminum oxide film formed on the polymer resin film must be 6 nm or more. If the total film thickness is less than 6 nm, the gas barrier performance cannot be satisfied.
The total thickness of the aluminum oxide film is preferably less than 50 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, it is preferable that the total film thickness is small, more preferably the total film thickness is 30.
It is less than nm.

In the transparent gas barrier film of the present invention, at least one incompletely oxidized layer containing a 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 and the degree of the aluminum metal component contained in the aluminum oxide film are X-ray photoelectron spectroscopy (hereinafter referred to as XPS) which is an analysis method having a very high surface sensitivity.
It can be determined by the Al2p spectrum by analysis. That is, the peak (Al (II
When it has an Al (0) peak indicating the presence of a metal component other than I)), 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 changes in the Al2p spectrum along the depth direction of the aluminum oxide film (hereinafter referred to as depth profile). That is, "the aluminum metal component is contained only in the aluminum oxide film" means that the Al (0) peak is not recognized in the XPS analysis from the surface, and the Al (0) peak is present in the depth profile. It was recognized that Al was re-applied near the interface with the polymer resin film substrate
(0) means that no peak is observed.

The content of the metal component of aluminum inside the aluminum oxide film is specified by the following definition.
That is, when the depth profile of the Al2p spectrum by the XPS analysis is taken, the interface between the aluminum oxide film surface and the polymer resin film substrate is Al as described above.
Although only (III) indicates a complete oxide film, a spectrum showing the presence of a metal component of Al (0) is obtained in addition to the spectrum of Al (III) inside. This A in Figure 1
An example of the spectra of l (III) and Al (0) is shown.
1 is a peak due to Al (III), and 2 is an Al (0) peak indicating the presence of a metal component. Depth from the surface d
The peaks of the spectrum in (nm unit) were divided, and the values obtained by converting the peak areas of Al (III) and Al (0) into the relative numbers of aluminum atoms belonging to each were N ₃ (d) and N ₀ (d), respectively. ), And the abundance ratio M (d) (unit%) of the aluminum metal component at that depth is defined as 100 × N ₀ (d) / (N ₃ (d) + N ₀ (d)). The horizontal axis represents the depth d from the surface (unit: nm), and the vertical axis represents the abundance ratio M of the aluminum metal component at that depth.
Draw a graph of (d) (unit:%). An example of the depth profile of M (d) thus obtained is shown in FIG.
Shown in. 4 is M (d) and 3 is (100-M
(D)), that is, the profile of aluminum belonging to Al (III). 5 is a carbon component of the polymer resin film substrate. Here, if the integration of M (d) in the depth d direction (d = 0 to d = total thickness of aluminum oxide film) is taken, a value having a unit of% .nm is obtained. This value corresponds to the amount of aluminum metal present in the aluminum oxide film and is defined as the aluminum metal component content. In the transparent gas barrier film of the present invention, the value of the aluminum metal component content is preferably 0.5% · nm to 10% · nm, and more preferably 1% · nm to 10% · nm. If it is less than 0.5% · nm, the gas barrier property is insufficient, and if it is more than 10% · nm, the light transmittance is lowered, and the desired transparent film having excellent gas barrier property can be obtained. Can not. In order to obtain a higher gas barrier property, 1% · nm to 10% · nm is more preferable.

The transparency of the aluminum oxide film portion is
It is represented by the ratio of the light transmittance of the polymer resin film after providing the aluminum oxide film to the light transmittance of the polymer resin film substrate at a wavelength of 550 nm (this is defined as the specific light transmittance). In the transparent gas barrier film of the present invention, the value of the specific light transmittance is preferably 90% or more, and more preferably 95% or more in order to make it easy to confirm the state of the contents.

The transparent gas barrier film of the present invention has an oxygen transmission rate of ² cc / m ² · day or less (more preferably 1 cc / m ² · day or less) and a water vapor transmission rate of 2 g.
/ M ² · day or less (more preferably 1g / m ² · da
y or less) is preferable.

Although at least one layer containing a metal component of aluminum is present inside the aluminum oxide film of the transparent gas barrier film of the present invention, two or more layers may be present. As for the number of layers, the horizontal axis as shown in FIG. 2 represents the depth d (nm unit) from the surface, and the vertical axis represents the abundance ratio M (d) (% unit) of the metal component of aluminum at that depth. It can be judged by the shape of the distribution of M (d) in the taken graph.

Next, a method for producing the transparent gas barrier film of the present invention will be described.

Any known method can be applied to the means for obtaining the polymer resin film substrate used in the present invention.

The method for forming the aluminum oxide film in the present invention is by reactive vapor deposition in an oxygen atmosphere. The oxygen atmosphere means an oxygen gas alone or an oxygen gas diluted with an inert gas and introduced into a vacuum vapor deposition machine in a required amount. The inert gas refers to a rare gas such as Ar or He, a nitrogen gas, or a mixed gas thereof. What is reactive vapor deposition? A method of evaporating aluminum from an evaporation source in such an oxygen atmosphere and causing an oxidation reaction near the polymer resin film base material to form aluminum oxide on the polymer resin film base material. Is. The evaporation source for this purpose includes, but is not particularly limited to, a resistance heating type boat type, a crucible type using radiation or high frequency heating, and an electron beam heating type.

In order to form the aluminum oxide film having the constitution of the present invention, the relationship between the beam intensity of aluminum vapor deposited on the polymer resin film substrate and the oxygen partial pressure in the vicinity of the polymer resin film substrate is important. Is.

FIG. 3 shows a general positional relationship between an evaporation source and a film when vapor deposition is continuously carried out on a film-shaped substrate. Cooling drum 7 arranged above evaporation source 6
Is rotated to supply the polymer resin film 8 to this drum. Generally, a deposition preventive plate 9 having an opening is provided right above the evaporation source having the strongest beam intensity of aluminum vapor from the evaporation source, and vapor deposition is performed from the opening onto the polymer resin film substrate. Considering the opening positions 10, 11, and 12 when the opening is large, 11 has the highest beam intensity of aluminum vapor,
10 and 12 are weak.

Only in the space above the deposition-inhibitory plate 9, aluminum can be completely oxidized with respect to the beam intensity of aluminum vapor in the space which is uniform and in the vicinity of 10 and 12, but aluminum in the vicinity of 11. When a partial pressure of oxygen is applied to the beam intensity of the vapor that does not sufficiently oxidize aluminum, a fully oxidized layer in which oxygen is sufficiently supplied is formed in the vicinity of 10 and 12, that is, at the beginning of deposition and at the end of deposition. In the central part of 11, an incomplete oxide layer with insufficient oxygen is formed. FIG. 4 shows positions 10 and 1 in this case.
The relationship between the aluminum vapor strengths 1 and 12 and the oxygen partial pressure will be described. As is generally known, the vapor intensity in the direction of the angle θ from the normal to the evaporation source is proportional to cos ⁿ θ (n is a value of 2 to 4), and the aluminum vapor intensity is as shown in FIG. Take the distribution.

In the method of applying a uniform oxygen partial pressure to the entire space including the space below the deposition-inhibitory plate 9, that is, in the case where an oxygen atmosphere is uniformly introduced into the upper and lower portions of the deposition-inhibitory plate, the structure of the present invention is used. It becomes extremely difficult to obtain an aluminum oxide film having 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 rapidly 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.

When the oxygen atmosphere is introduced from the vicinity of the opening as shown in FIG. 5 from the direction of 15, the oxygen partial pressure decreases in the directions of 10, 11 and 12 as shown in FIG. The position where the different layers are formed is shifted to the 12 side. Therefore, a layer containing a metal component is formed relatively near the surface. Further, it can be easily estimated that a layer containing a metal is formed in the central portion even when the oxygen atmosphere is introduced from both the vicinity of 10 and 12.

In any case, in order to obtain the transparent gas barrier film of the present invention, it is essential to introduce an oxygen atmosphere near the vapor deposition portion (near the polymer resin film substrate). In addition, surrounding the region where oxygen is consumed as shown in FIG. 5 accurately controls the relationship between the beam intensity of aluminum vapor and the oxygen partial pressure described above, uses oxygen efficiently, and uses it in an exhaust pump more than necessary. It is also important not to load.

Incidentally, the conventionally known Japanese Patent Laid-Open No. 62-22033.
In Japanese Patent Laid-Open No. 0-0,009, when the aluminum oxide film contains 1 to 15% by weight of the aluminum metal component, 1% by weight or more of the aluminum metal component is recognized by XPS analysis of the vapor deposition surface. However, it is essentially different from the configuration of the present invention.

[0030]

[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 total film thickness was determined by the peak intensity of aluminum by fluorescent X-ray spectroscopy calibrated by cross-sectional observation 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 intensity of the aluminum peak of the fluorescent X-rays and the actual total film thickness are in good proportion.

(2) Content of aluminum metal component 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. The calculation method is as described above.

(3) Water Vapor Transmission Rate Water vapor transmission rate measuring device (manufactured by Honeywell Co., W82)
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 by using an oxygen permeability measuring device (OX-TRAN100 manufactured by Modern Control Co.).

(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.

[0036]

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

Examples 1 to 5 and Comparative Examples 1 to 2 Samples were prepared with the structure of the vapor deposition portion shown in FIG. The evaporation source is a system by electron beam heating, and 99.99% aluminum metal was loaded into an alumina crucible for vapor deposition. The film is a polyethylene terephthalate (hereinafter referred to as PET) film "Lumirror" P6 manufactured by Toray Industries, Inc.
0 (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 5 × 10 ⁻⁵ Torr or less, the film is run, and electric power is supplied to the electron beam evaporation source to start aluminum vapor deposition. After adjusting the electric power of the evaporation source to a desired evaporation rate using an in-line light transmittance meter and a resistivity meter, 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. A sample was obtained by increasing the film running speed to obtain the desired total film thickness.

Table 1 shows the characteristics of Examples 1 to 5 and Comparative Examples 1 and 2 and the original PET film thus prepared.
In all of these samples, it was confirmed by XPS analysis depth profile that a complete oxide film was formed at the interface between the surface of the aluminum oxide film and the PET film.

[0039]

[Table 1] The specific light transmittance is 95% or more in both Examples and Comparative Examples, but the gas barrier property is not sufficient when the film thickness is 6 nm or less.

Examples 6 to 10 and Comparative Examples 3 to 7 Table 2 shows Examples and Comparative Examples in which the content of the metal component of aluminum was changed. Similarly, all samples are XPS
It was confirmed from the depth profile of the analysis that a complete oxide film was formed at the interface between the surface of the aluminum oxide film and the PET film.

[0041]

[Table 2] When the aluminum content of the layer in which aluminum metal is present is extremely small or no aluminum metal is observed at all according to the depth profile of XPS analysis, the specific light transmittance is very high and transparent regardless of the total film thickness. However, the gas barrier property is not sufficient. Further, as shown in Comparative Examples 6 and 7, regardless of the total film thickness, when the aluminum metal content exceeds 10% · nm, the gas barrier property is good, but the specific light transmittance sharply decreases and a brown color appears. This is not preferable because the coloring of the above becomes remarkable.

Comparative Examples 8 to 9 Table 3 shows the results when only aluminum metal was vapor-deposited without introducing oxygen during vapor deposition. In this case, the aluminum metal component is also found at the interface between the surface of the aluminum oxide film and the PET film, but the aluminum metal component content can be similarly determined.

[0043]

[Table 3] Regardless of the size of the total film thickness, the gas barrier property is insufficient and the specific light transmittance is low.

[0044]

The transparent gas barrier film of the present invention comprises
Because of the above-mentioned structure, it has a high light transmittance and a high gas barrier property against oxygen and water vapor. In addition, there is no yellowish coloring, and it has practically sufficient processing suitability.

This transparent gas barrier film 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. Further, since the film of the present invention has a high microwave transmittance, it can meet the demand for cooking the contents in a microwave oven as it is in a packaged state.

The transparent gas barrier film of the present invention can be used alone, but may be further printed, coated with a protective layer or the like on the aluminum oxide film, laminated with another film, or It is also possible to use them after further processing such as combining them.

[Brief description of drawings]

FIG. 1 X of an incompletely oxidized layer containing an aluminum metal component.
It is an example of the spectrum of PS analysis.

FIG. 2 is an example of a depth profile of a composition ratio of an aluminum metal component and a complete oxidation component of a vapor deposition film having one layer of the aluminum metal component only inside the film.

FIG. 3 is a schematic diagram of a vapor deposition portion of a continuous vapor deposition machine that performs vapor deposition on a film-shaped substrate.

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

FIG. 5 is a vapor deposition part of a continuous vapor deposition machine for performing vapor deposition on a film-shaped substrate as in FIG. 3, but is a schematic diagram in the case where gas introduction for reactive vapor deposition is performed from the film unwinding side.

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

[Explanation of symbols] 1: Aluminum oxide component Al (III) in XPS analysis
Spectra 2: XPS analysis aluminum metal component Al (0) spectrum 3: Al (III) composition ratio profile 4: Al (0) composition ratio profile 5: Carbon component profile in original PET film 6: evaporation source 7: cooling drum 8: film 9: deposition plate 10: vapor deposition position 11: same as above 12: same as above 13: drum rotation direction 14: aluminum vapor 15: oxygen introduction route 16: prevention when vapor deposition part is enclosed Plate

Claims (2)

[Claims] 1. A film in which an aluminum oxide film is formed on at least one surface of a polymer resin film substrate, the total thickness of the aluminum oxide film is 6 nm or more, and an aluminum metal component is contained. At least one incomplete oxide layer exists only inside the aluminum oxide film, and the content of the aluminum metal component in the entire aluminum oxide film is in the range of 0.5% · nm to 10% · nm. A transparent gas barrier film characterized by: 2. The specific light transmittance at a wavelength of 550 nm is 90% or more, and the oxygen transmittance is ² cc / m ² ·.
Water vapor permeability of 2g / m ² · day or less
The transparent gas barrier film according to claim 1, wherein: