JP7489026B2 - Barrier Films and Packaging Materials - Google Patents

Description

The present invention relates to a barrier film, and more specifically to a barrier film comprising a barrier coat layer, an inorganic oxide vapor deposition layer, and a substrate layer in this order. The present invention also relates to a packaging material comprising the barrier film.

Conventionally, packaging materials used for packaging food, daily necessities, pharmaceuticals, etc., need to prevent the contents from deteriorating and maintain their functions and properties, and must be protected from the effects of oxygen, water vapor, and other gases that degrade the contents, which permeate the packaging material. They are therefore required to have gas barrier properties to block these gases. For this reason, films of vinylidene chloride resins, which have excellent gas barrier properties among polymers, or films coated with these resins, have been commonly used. However, the gas barrier properties of these materials are significantly affected by factors such as temperature and humidity, and there has been a technical challenge in that they cannot meet the demand for high levels of gas barrier properties.

For items that require a high level of gas barrier properties, packaging materials that use metal foils made of aluminum or other metals as a gas barrier layer have been used. However, while packaging materials that use metal foils made of aluminum or other metals have high gas barrier properties and are not affected by temperature or humidity, there are technical issues with them, such as the inability to see through the packaging material to check the contents, the need to dispose of them as non-combustible waste after use, and the inability to use metal detectors during inspection.

In recent years, to solve these technical problems, vapor-deposited films, in which a vapor-deposited thin layer of inorganic oxides such as silicon oxide, aluminum oxide, and magnesium oxide is laminated on a polymer film by a forming method such as vacuum deposition or sputtering, have been used as packaging materials. These vapor-deposited films are considered to be suitable as packaging materials that have both transparency and gas barrier properties that cannot be obtained with metal foils, etc. However, even such gas barrier laminated films have a technical problem in that their gas barrier properties decrease when sterilized at high temperatures.

In order to solve these technical problems, a gas barrier laminate film has been proposed that includes a resin substrate, a gas barrier deposition layer that is provided on the resin substrate and contains mainly inorganic compounds, and a gas barrier coating layer that is provided on the gas barrier deposition layer and is obtained by applying and drying a coating liquid that contains a specific silicon compound and its hydrolysate, as well as a water-soluble polymer having a hydroxyl group (see Patent Document 1).

International Publication No. 2004-048081

However, even the gas barrier laminate film proposed in Patent Document 1 still exhibits deterioration in gas barrier properties after moist heat sterilization, so there is still a demand for gas barrier properties that are resistant to deterioration even after moist heat sterilization.

The present invention has been made in view of the above-mentioned background art, and its purpose is to provide a barrier film whose gas barrier properties are resistant to deterioration even after moist heat sterilization treatment. It is also an object of the present invention to provide a packaging material with excellent barrier properties for retort packaged products using such a barrier film.

The inventors conducted extensive research to solve the above problems, and discovered that in a barrier film comprising a barrier coat layer, an inorganic oxide vapor deposition layer, and a substrate layer in this order, the above problems can be solved by adjusting the ratio of silicon atoms to carbon atoms (Si/C) measured by X-ray photoelectron spectroscopy (XPS) on the surface of the barrier coat layer to within a specific range. The present invention was completed based on this discovery.

That is, according to one aspect of the present invention,
A barrier film comprising a barrier coat layer, an inorganic oxide vapor deposition layer, and a substrate layer in this order,
the barrier coat layer is a cured film of a barrier coat composition containing a hydrolysis product of an alkoxysilane and a water-soluble polymer,
A barrier film is provided in which the surface of the barrier coat layer has a ratio of silicon atoms to carbon atoms (Si/C) of 1.0 or more and 2.5 or less as measured by X-ray photoelectron spectroscopy (XPS).

In the above aspect of the present invention, it is preferable that the surface of the barrier coat layer has a ratio of silicon atoms to carbon atoms (Si/C) measured by X-ray photoelectron spectroscopy (XPS) of 1.6 or more and 2.3 or less.

In the above aspect of the present invention, it is preferable that the surface of the barrier coat layer has a ratio of silicon atoms to carbon atoms (Si/C) measured by X-ray photoelectron spectroscopy (XPS) of 1.0 or more and less than 1.6.

In the above aspect of the present invention, it is preferable that the inorganic oxide vapor deposition layer is an aluminum oxide vapor deposition film or a silicon oxide vapor deposition film.

In the above aspect of the present invention, it is preferable that the barrier coat composition further contains a silane coupling agent.

In the above aspect of the present invention, it is preferable that the substrate layer is a polyester film derived from biomass.

In the above aspect of the present invention, the inorganic oxide vapor deposition layer is an aluminum oxide vapor deposition film,
a transition region is formed in the aluminum oxide vapor-deposited film, the transition region defining a peel strength between the surface of the base layer and the aluminum oxide vapor-deposited film;
the transition region contains elementally bonded Al ₂ O ₄ H which transforms into aluminum hydroxide, as detected by etching using time-of-flight secondary ion mass spectrometry (TOF-SIMS);
It is preferable that the transformation rate of the transition region, which is defined by the ratio of the transformed transition region to the aluminum oxide vapor deposition film determined by etching the barrier coat layer and the aluminum oxide vapor deposition film using TOF-SIMS, is 5% or more and 60% or less.

In the above aspect of the present invention, the barrier film preferably has an oxygen permeability of 0.10 cc/m ² ·atm ·day or less, measured in accordance with JIS K7126 under an environment of a temperature of 23° C. and a humidity of 90% RH.

In the above aspect of the present invention, the barrier film preferably has a water vapor permeability of 1.00 g/m ² ·day or less, measured in accordance with JIS K7129 under an environment of a temperature of 40° C. and a humidity of 100% RH.

According to another aspect of the present invention, a packaging material is provided that includes the above-mentioned barrier film.

In another aspect of the present invention, the packaging material preferably comprises, in this order, a heat seal layer, an intermediate layer, and a barrier layer made of the barrier film.

In another aspect of the present invention, the packaging material preferably has an oxygen permeability of 0.50 cc/m2·atm·day or less, measured in accordance with JIS K7126 under an environment of a temperature of 23°C and a humidity of 90% RH after moist heat sterilization at 135 ^° C for 40 minutes.

In another aspect of the present invention, the packaging material preferably has a water vapor permeability of 1.20 g/m2·day or less, measured in accordance with JIS K7129 under an environment of a temperature of 40°C and a humidity of 100% RH after moist heat sterilization at 135°C for ⁴⁰ minutes.

According to another aspect of the present invention, there is provided a packaging material comprising the above-mentioned barrier film,
After moist heat sterilization at 135° C. for 40 minutes, the normal peel strength between the base layer and the aluminum oxide vapor-deposited film measured in accordance with JIS K6854-2 is preferably 1.0 N or more.

According to another aspect of the present invention, it is preferable that the packaging material comprising the above-mentioned barrier film has a water-exfoliation peel strength of 1.0 N or more between the base layer and the aluminum oxide vapor-deposited film measured in accordance with JIS K6854-2 after moist heat sterilization at 135°C for 40 minutes.

In another aspect of the present invention, the packaging material is preferably for use in retort-packaged products.

According to the present invention, it is possible to provide a barrier film whose gas barrier properties are resistant to deterioration even after moist heat sterilization treatment. Furthermore, by using such a barrier film, it is possible to provide a packaging material with excellent barrier properties for retort packaged products.

FIG. 1 is a schematic cross-sectional view showing one embodiment of a barrier film of the present invention. FIG. 1 is a graph showing the analysis results of a barrier film having an aluminum oxide vapor deposition film by time-of-flight secondary ion mass spectrometry. FIG. 1 is a plan view showing an example of an apparatus for performing oxygen plasma pretreatment and forming an aluminum oxide vapor deposition film. 1 is a schematic cross-sectional view showing one embodiment of a packaging material of the present invention. FIG. 2 is a diagram showing an example of a method for measuring peel strength. FIG. 2 is a diagram showing an example of a method for measuring peel strength. FIG. 1 is a graph showing the change in tensile stress with respect to the distance between a pair of grippers that pull two films to measure peel strength.

<Barrier film>
The barrier film according to the present invention comprises a barrier coat layer, an inorganic oxide vapor deposition layer, and a substrate layer in this order. A barrier film having such a layer structure is resistant to deterioration of gas barrier properties even after moist heat sterilization. Such a barrier film can be suitably used as a barrier layer for retort packaged products that require gas barrier properties even after moist heat sterilization.

The oxygen transmission rate of the barrier film, measured in accordance with JIS K7126 under an environment of 23° C. and 90% RH, is preferably 0.10 cc/ ^m2 atm day or less, more preferably 0.08 cc/ ^m2 atm day or less, even more preferably 0.06 cc/ ^m2 atm day or less, and even more preferably 0.05 cc/ ^m2 atm day or less. If the oxygen transmission rate of the barrier film satisfies the above numerical range, it has suitable oxygen barrier properties, and therefore when used as a barrier layer of a packaging material, adverse effects on the contents of the packaging material can be suppressed.

The barrier film has a water vapor permeability, measured in accordance with JIS K7129 under an environment of a temperature of 40°C and a humidity of 100% RH, of preferably 1.00 g/ ^m2 ·day or less, more preferably 0.70 g/ ^m2 ·day or less, even more preferably 0.60 g/ ^m2 ·day or less, and even more preferably 0.50 g/ ^m2 ·day or less.
If the water vapor permeability of the barrier film falls within the above numerical range, it has suitable water vapor barrier properties, and therefore when used as a barrier layer of a packaging material, adverse effects on the contents of the packaging material can be suppressed.

The layer structure of the barrier film of the present invention will be described with reference to the drawings. The barrier film 11 shown in FIG. 1 has an inorganic oxide deposition layer 13 on one side of a substrate layer 12, and a barrier coat layer 14 on the inorganic oxide deposition layer 13. Each layer constituting the barrier film of the present invention will be described below.

(Base layer)
The substrate layer used in the barrier film of the present invention is not particularly limited, but may be a resin film (hereinafter also referred to as substrate film) that has excellent chemical and physical strength, can withstand conditions for forming a vapor-deposited film of an inorganic oxide, and can maintain its film properties well without impairing them. Specifically, for example, films of various resins may be used, such as polyolefin resins such as polyethylene resins or polypropylene resins, cyclic polyolefin resins, polystyrene resins, acrylonitrile-styrene copolymers (AS resins), acrylonitrile-butadiene-styrene copolymers (ABS resins), poly(meth)acrylic resins, polycarbonate resins, polyvinyl alcohol resins, saponified ethylene-vinyl ester copolymers, polyester resins such as polyethylene terephthalate, polyethylene naphthalate, and polyethylene furanoate, polyamide resins such as various nylons, polyurethane resins, acetal resins, and cellulose resins. In the present invention, among the above-mentioned resin films, it is particularly preferable to use films of polyester resins, polyolefin resins, or polyamide resins. The substrate layer may be any of the above-mentioned resin unstretched films and resin films stretched uniaxially or biaxially.

In addition to polyethylene terephthalate, which is a common polyester resin film derived from petroleum fuels, the following polyester films can also be used.

(Polybutylene terephthalate film (PBT))
Since polybutylene terephthalate films have a high heat distortion temperature, excellent mechanical strength and electrical properties, and good moldability, when used in packaging bags for containing food and other contents, they can prevent the packaging bag from being deformed or its strength from being reduced during retort treatment. The polybutylene terephthalate film is a film containing polybutylene terephthalate (hereinafter also referred to as PBT) as a main component, and is preferably a resin film containing 60% by mass or more of PBT.

(Biomass-derived polyester film)
The biomass-derived polyester film is made of a resin composition containing a polyester composed of diol units and dicarboxylic acid units as a main component, and the diol units of the resin composition are ethylene glycol derived from biomass. The biomass-derived polyester film may contain, based on the entire resin composition, preferably 50 to 95 mass %, more preferably 50 to 90 mass %, of a polyester whose dicarboxylic acid units are dicarboxylic acids derived from fossil fuels.

Biomass-derived ethylene glycol is made from ethanol (biomass ethanol) produced from biomass such as sugar cane and corn. For example, biomass-derived ethylene glycol can be obtained by converting biomass ethanol into ethylene oxide using a conventional method. Commercially available biomass ethylene glycol may also be used; for example, biomass ethylene glycol available from India Glycoal Limited can be suitably used.

The dicarboxylic acid units of the polyester use dicarboxylic acids derived from fossil fuels. As the dicarboxylic acid, aromatic dicarboxylic acids, aliphatic dicarboxylic acids, and derivatives thereof can be used. As the aromatic dicarboxylic acid, terephthalic acid and isophthalic acid can be mentioned, and as the derivatives of aromatic dicarboxylic acids, lower alkyl esters of aromatic dicarboxylic acids, specifically, methyl esters, ethyl esters, propyl esters, butyl esters, and the like can be mentioned. Among these, terephthalic acid is preferred, and as the derivatives of aromatic dicarboxylic acids, dimethyl terephthalate is preferred.

The resin composition forming the biomass-derived polyester film may contain one or more of the following: polyester derived from fossil fuels, recycled polyester from polyester products derived from fossil fuels, and recycled polyester from polyester products derived from biomass. The resin composition forming the biomass-derived polyester film may contain one or more of the following: polyester derived from fossil fuels, recycled polyester from polyester products derived from fossil fuels, and recycled polyester from polyester products derived from biomass, at a ratio of 5 to 45% by mass.

Carbon dioxide in the atmosphere contains a certain proportion of ¹⁴ C (105.5 pMC), and it is known that ^{the 14} C content in plants that grow by absorbing carbon dioxide from the atmosphere, such as corn, is also about 105.5 pMC. It is also known that fossil fuels contain almost no ¹⁴ C. Therefore, by measuring the proportion of ¹⁴ C in the total carbon atoms in polyester, the proportion of carbon derived from biomass can be calculated.
In the present invention, the "biomass degree" refers to the weight ratio of biomass-derived components. Taking PET as an example, since PET is a polymer of ethylene glycol containing 2 carbon atoms and terephthalic acid containing 8 carbon atoms in a molar ratio of 1:1, when only biomass-derived ethylene glycol is used, the weight ratio of biomass-derived components in PET is 31.25%, and the biomass degree is 31.25% (molecular weight derived from biomass-derived ethylene glycol/molecular weight of one polymerization unit of polyester=60÷192).
In addition, the weight ratio of the biomass-derived component of the fossil fuel-derived polyester is 0%, and the biomass degree of the fossil fuel-derived polyester is 0%. In the present invention, the biomass degree in the base layer is preferably 5.0% or more, more preferably 10.0% or more. In addition, the biomass degree in the base layer is preferably 30.0% or less.

(recycled polyethylene terephthalate)
A polyethylene terephthalate film containing polyethylene terephthalate recycled by mechanical recycling, specifically, PET obtained by mechanically recycling PET bottles, the diol component of which is ethylene glycol, and the dicarboxylic acid components of which are terephthalic acid and isophthalic acid. The content of the isophthalic acid component in the total dicarboxylic acid components constituting the PET is preferably 0.5 mol % or more and 5 mol % or less, more preferably 1.0 mol % or more and 2.5 mol % or less.

Mechanical recycling is a method in which collected polyethylene terephthalate resin products such as PET bottles are generally crushed and washed with an alkali to remove dirt and foreign matter from the surface of the PET resin products, and then the products are dried at high temperature and reduced pressure for a certain period of time to diffuse and decontaminate the contaminants remaining inside the PET resin, removing dirt from the resin products made of PET resin and returning them to PET resin.

Recycled polyethylene terephthalate preferably contains recycled PET at a ratio of 50% by weight to 95% by weight, and may also contain virgin PET. Virgin PET may contain ethylene glycol as a typical diol component and terephthalic acid as a dicarboxylic acid component, or may further contain isophthalic acid.

As the films of the various resins mentioned above, for example, one or more of the various resins mentioned above can be used to form a film from the various resins alone using a film-forming method such as extrusion, cast molding, T-die, cutting, or inflation, or two or more types of resins can be used to form a multilayer film by co-extrusion, or two or more types of resins can be used to form a film by mixing them before forming into a film. If necessary, films of the various resins can be stretched uniaxially or biaxially using, for example, a tenter method or a tubular method.

The thickness of the various resin films is preferably about 6 to 2000 μm, and more preferably about 9 to 100 μm.

When one or more of the above resins are used to form a film, various plastic compounding agents and additives can be added to improve or modify the film's processability, heat resistance, weather resistance, mechanical properties, dimensional stability, oxidation resistance, slipperiness, release properties, flame retardancy, mold resistance, electrical properties, strength, etc. The amount of additives can range from very small amounts to several tens of percent, and can be added at will depending on the purpose.

In the above, typical additives that can be used include, for example, lubricants, crosslinking agents, antioxidants, UV absorbers, light stabilizers, fillers, reinforcing agents, antistatic agents, pigments, etc., and further, modifying resins, etc. can also be used.

In the present invention, the substrate layer may be subjected to a surface treatment before forming an inorganic oxide deposition film on the substrate layer. This can improve adhesion to the inorganic oxide deposition film. Similarly, a surface treatment can be performed on the deposition layer to improve adhesion to the gas barrier coating film. Examples of such surface treatments include pretreatments such as corona discharge treatment, ozone treatment, low-temperature plasma treatment using oxygen gas or nitrogen gas, glow discharge treatment, and oxidation treatment using chemicals.

Surface treatment can also be performed by applying a primer coating agent, an undercoat agent, or a vapor deposition anchor coating agent, as desired. Examples of the coating agent include polyester resins, polyamide resins, polyurethane resins, epoxy resins, phenol resins, (meth)acrylic resins, polyvinyl acetate resins, polyolefin resins such as polyethylene or polypropylene, or copolymers or modified resins thereof, and resin compositions containing cellulose resins as the main component of the vehicle.

Among these surface treatments, corona treatment and plasma treatment are particularly suitable. For example, plasma treatment is a method of surface modification using plasma gas generated by ionizing gas by arc discharge. Inorganic gases such as oxygen gas, nitrogen gas, argon gas, and helium gas can be used as the plasma gas. For example, by performing plasma treatment in-line, moisture and dust on the surface of the substrate layer can be removed, and the surface can be smoothed, activated, and otherwise treated. Plasma treatment can also be performed after deposition to improve adhesion. In the present invention, plasma discharge treatment is preferably performed as the plasma treatment, taking into consideration the plasma output, type of plasma gas, supply amount of plasma gas, treatment time, and other conditions. In addition, devices such as direct current glow discharge, high frequency discharge, and microwave discharge can be used as a method of generating plasma. Plasma treatment can also be performed by atmospheric pressure plasma treatment.

(Inorganic oxide vapor deposition layer)
The vapor-deposited layer constituting the barrier film according to the present invention is a vapor-deposited film of an inorganic oxide formed by a chemical vapor deposition method (CVD method) or a physical vapor deposition method (PVD method).

The inorganic oxide is not particularly limited, but a vapor deposition film of an oxide of silicon, aluminum, magnesium, calcium, potassium, tin, sodium, boron, titanium, lead, zirconium, yttrium, or the like can be used. In particular, the inorganic oxide vapor deposition layer is preferably a vapor deposition film of aluminum oxide or silicon oxide, and more preferably a vapor deposition film of aluminum oxide. The inorganic oxide is expressed, for example, as MO _{x (} wherein M represents an inorganic element, and the value of X varies depending on the inorganic element), such as _AlO x or SiO x. In the present invention, from the viewpoint of transparency and gas barrier property, when M is aluminum (Al), the value of X is preferably 0.5 to 2.0, and when M is silicon (Si), the value of X is preferably 1 to 2.

As the inorganic oxide deposition layer, it is preferable to provide an aluminum oxide deposition film by physical vapor deposition, because it is easy to handle as a deposition material. The aluminum oxide deposition film formed by physical vapor deposition has excellent adhesion to the surface of the gas barrier coating film. Examples of physical vapor deposition methods include physical vapor deposition methods (Physical Vapor Deposition method, PVD method) such as vacuum deposition method, sputtering method, ion plating method, and ion cluster beam method.

Specifically, the deposition film can be formed using a vacuum deposition method in which aluminum or its oxide is used as a raw material, which is heated to vaporize and then deposited on one side of the substrate layer; an oxidation reaction deposition method in which aluminum or its oxide is used as a raw material, which is oxidized by introducing oxygen and then deposited on one side of the substrate layer; or a plasma-assisted oxidation reaction deposition method in which the oxidation reaction is assisted by plasma. The deposition material can be heated, for example, by resistance heating, high-frequency induction heating, electron beam heating (EB), etc.

In addition, when the inorganic oxide deposition layer is a silicon oxide deposition film, it is preferable to provide the silicon oxide deposition film by chemical vapor deposition from the viewpoint of bending resistance and gas barrier properties. Examples of chemical vapor deposition methods include chemical vapor deposition methods (chemical vapor deposition methods, CVD methods) such as plasma chemical vapor deposition, low-temperature plasma chemical vapor deposition, thermal chemical vapor deposition, and photochemical vapor deposition. Specifically, a silicon oxide deposition film can be formed on one side of the substrate layer by using a low-temperature plasma chemical vapor deposition method that uses a deposition monomer gas such as an organic silicon compound as a raw material, an inert gas such as argon gas or helium gas as a carrier gas, and oxygen gas as an oxygen supply gas, and uses a low-temperature plasma generator or the like. As the low-temperature plasma generator, for example, a generator such as a high-frequency plasma, a pulse wave plasma, or a microwave plasma can be used. It is preferable to use a generator using a high-frequency plasma method in that a highly active and stable plasma can be obtained.

As the vapor deposition monomer gas of the organosilicon compound that forms the silicon oxide vapor deposition film, for example, 1,1,3,3-tetramethyldisiloxane, hexamethyldisiloxane, vinyltrimethylsilane, methyltrimethylsilane, hexamethyldisilane, methylsilane, dimethylsilane, trimethylsilane, diethylsilane, propylsilane, phenylsilane, vinyltriethoxysilane, vinyltrimethoxysilane, tetramethoxysilane, tetraethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, octamethylcyclotetrasiloxane, etc. can be used. Among these, it is particularly preferable to use 1,1,3,3-tetramethyldisiloxane or hexamethyldisiloxane as a raw material in terms of its ease of handling and the properties of the continuous film formed. In addition, in the above, for example, argon gas, helium gas, etc. can be used as the inert gas.

The silicon oxide vapor deposition film is mainly composed of silicon oxide, but may further contain at least one compound consisting of one or more elements of carbon, hydrogen, silicon, or oxygen by chemical bonds, etc. For example, when a compound having a C-H bond, a compound having a Si-H bond, or a carbon unit is graphite-like, diamond-like, fullerene-like, etc., it may further contain a raw material organic silicon compound or a derivative thereof by chemical bonds, etc. For example, a hydrocarbon having a _CH3 site, hydrosilica such as _SiH3 silyl, _SiH2 silylene, and a hydroxyl group derivative such as _SiH2OH silanol can be mentioned. In addition to the above, the type and amount of the compound contained in the silicon oxide vapor deposition film can be changed by changing the conditions of the vapor deposition process, etc.

The thickness of the inorganic oxide deposition layer is preferably 3 to 50 nm, more preferably 8 to 30 nm, and even more preferably 9 to 14 nm. If the thickness of the inorganic oxide deposition layer is within the above range, the gas barrier properties are unlikely to deteriorate even after moist heat sterilization treatment.

In a preferred embodiment of the present invention, the inorganic oxide vapor-deposited layer is an aluminum oxide vapor-deposited film, and a transition region that determines the peel strength between the surface of the base layer and the aluminum oxide vapor-deposited film is formed in the aluminum oxide vapor-deposited film, and the transition region contains elementally bonded Al ₂ O ₄ H that is transformed into aluminum hydroxide as detected by etching using time-of-flight secondary ion mass spectrometry (TOF-SIMS), and a transformation rate of the transition region, defined as a ratio of the transformed transition region to the aluminum oxide vapor-deposited film as determined by etching the barrier coat layer and the aluminum oxide vapor-deposited film using TOF-SIMS, is 5% or more and 60% or less. This can improve the normal state adhesion and water-resistant adhesion of the interface between the base layer and the aluminum oxide vapor-deposited film of the barrier film after moist heat sterilization treatment at 135° C. for 40 minutes (high retort treatment) or moist heat sterilization treatment at 121° C. for 40 minutes (semi-retort treatment), and can make the gas barrier property less susceptible to deterioration. The transformation rate of the transition region is preferably 5% or more and 45% or less, and more preferably 5% or more and 30% or less.

The transition region is defined using time-of-flight secondary ion mass spectrometry (TOF-SIMS) for an aluminum oxide deposition film defined by etching using TOF-SIMS, including elementally bonded Al ₂ O ₄ H that transforms into aluminum hydroxide detected by etching using TOF-SIMS.

Secondary ion mass spectrometry (SIMS) is a method for analyzing elemental concentration distribution by irradiating the surface of a sample to be analyzed with a primary ion beam and performing mass analysis on the secondary ions that are sputtered and released from the sample surface. In this secondary ion mass spectrometry method, the secondary ion intensity is detected while sputtering is progressing. Therefore, by converting the transition time into depth for data on the time transition of the ion intensity of the secondary ions, i.e., the ions of the element to be detected or molecular ions bonded to the element to be detected, the concentration distribution of the element to be detected in the depth direction of the sample surface can be known.

The conversion of transition time to depth is done by using a surface roughness meter to measure the depth of the depression formed on the sample surface by the irradiation of primary ions, calculating the average sputtering rate from this depression depth and transition time, and converting the irradiation time (i.e., transition time) to depth (amount of sputtering) under the assumption that the sputtering rate is constant.

By repeatedly soft-etching the aluminum oxide vapor-deposited film of the varifilm at the above-mentioned constant speed with a Cs (cesium) ion gun, and measuring ions derived from the aluminum oxide vapor-deposited film and ions derived from the base layer using time-of-flight secondary ion mass spectrometry (TOF-SIMS), a transition region that determines the peel strength is formed between the surface of the base layer and the vapor-deposited film mainly composed of the aluminum oxide vapor-deposited film. The transition region contains elemental bond Al ₂ O ₄ H that is transformed into aluminum hydroxide, which is detected by etching using time-of-flight secondary ion mass spectrometry (TOF-SIMS), and by specifying the transformation rate of the transition region that is transformed into aluminum hydroxide, which is defined by the ratio of the transformed transition region defined by time-of-flight secondary ion mass spectrometry to the aluminum oxide vapor-deposited film defined by etching using time-of-flight secondary ion mass spectrometry (TOF-SIMS), a barrier film having barrier properties with improved normal adhesion and water-resistant adhesion can be specified.

Specifically, etching is performed from the outermost surface of the aluminum oxide vapor-deposited film with Cs using a time-of-flight secondary ion mass spectrometer, the elemental bonds at the interface between the aluminum oxide vapor-deposited film and the base layer and the elemental bonds in the vapor-deposited film are measured, and actual measurement graphs are obtained for each of the measured elements and elemental bonds (Figure 2: graph analysis diagram). In order to narrow as much as possible the transition region at the interface between the base layer and the vapor-deposited film formed by aluminum hydroxide in the aluminum oxide vapor-deposited film, attention is focused on the elemental _{bond Al2O4H} , and 1) the position where the intensity of the graph of element _C6 is half is determined as the interface between the base layer and aluminum oxide, and the region from the surface to the interface is determined as the aluminum _{oxide vapor-deposited film, 2) the peak in the graph representing the elemental bond Al2O4H is} determined, and the region from the peak to the interface is determined as the transition region, and 3) the conversion rate to aluminum _hydroxide in the transition region is determined as (transition region from the peak of the elemental bond _Al2O4H to the interface/aluminum oxide vapor-deposited film) x 100 (%).

In one embodiment, the aluminum oxide vapor deposition film is preferably formed by performing oxygen plasma pretreatment on the surface of the base layer using a plasma pretreatment device described below. This allows the formation of an aluminum oxide vapor deposition film having a conversion rate in the transition region described above, and improves the normal state adhesion and water-resistant adhesion between the base layer and the aluminum oxide vapor deposition film. The oxygen plasma treatment is performed with a bias voltage perpendicular to the base layer. The oxygen plasma pretreatment is a pretreatment for further strengthening and improving the normal state adhesion and water-resistant adhesion between various resin films or sheets and the aluminum oxide vapor deposition film, and can be performed in the following device.

As shown in FIG. 3, the roller-type continuous vapor deposition film forming apparatus 20, which is suitable for use in the manufacture of barrier films having aluminum oxide vapor deposition films, has partitions 45a to 45c formed in the decompression chamber 22. The partitions 45a to 45c form the substrate transport chamber 22A, the plasma pretreatment chamber 22B, and the film formation chamber 22C. In particular, the plasma pretreatment chamber 22B and the film formation chamber 22C are formed as spaces surrounded by the partitions and the partitions 45a to 45c, and each chamber further has an exhaust chamber formed inside as necessary.

In the plasma pretreatment chamber 22B, a plasma pretreatment roller 30 that transports the substrate film S to be pretreated and enables plasma treatment is provided so that a portion of the roller 30 is exposed to the substrate transport chamber 22A, and the substrate film S is moved to the plasma pretreatment chamber 22B while being wound up.

The plasma pretreatment chamber 22B and the deposition chamber 22C are provided adjacent to the substrate transport chamber 22A, and the substrate film S can be moved without being exposed to the atmosphere. The pretreatment chamber 22B and the substrate transport chamber 22A are connected by a rectangular hole, through which a part of the plasma pretreatment roller 30 protrudes toward the substrate transport chamber 22A, and a gap is opened between the wall of the transport chamber and the pretreatment roller 30, and the substrate film S can be moved from the substrate transport chamber 22A to the deposition chamber 22C through the gap. The same structure is also formed between the substrate transport chamber 22A and the deposition chamber 22C, and the substrate film S can be moved without being exposed to the atmosphere.

The substrate transport chamber 22A is provided with a winding roller as a winding means for winding up the substrate film S, which has a vapor deposition film formed on one side and has been moved back into the substrate transport chamber 22A by the deposition roller 33, into a roll, so that the substrate film S, which has a vapor deposition film formed on it, can be wound up.

When manufacturing a barrier film having an aluminum oxide vapor deposition film, the plasma pretreatment chamber 22B is configured to separate the space where the plasma is generated from other areas and to efficiently evacuate the opposing space, making it easier to control the plasma gas concentration and improving productivity. The pretreatment pressure formed by reducing the pressure can be set and maintained at approximately 0.1 Pa to 100 Pa, and in particular, the treatment pressure for oxygen plasma pretreatment is preferably 1 to 20 Pa to achieve a preferred transformation rate in the transition region of the aluminum oxide vapor deposition film.

The transport speed of the base film S is not particularly limited, but from the viewpoint of production efficiency, it can be at least 200 to 1000 m/min. In particular, the transport speed for oxygen plasma pretreatment is preferably 300 to 800 m/min in order to obtain the transformation rate in the transition region of the aluminum oxide vapor deposition film.

The plasma pretreatment roller 30 that constitutes the plasma pretreatment device is intended to prevent the substrate film S from shrinking or being damaged by heat during plasma treatment by the plasma pretreatment means, and to apply oxygen plasma P to the substrate film S uniformly and over a wide area.
It is preferable that the pretreatment roller 30 can be adjusted to a constant temperature between −20° C. and 100° C. by adjusting the temperature of a temperature adjustment medium circulating within the pretreatment roller.

The plasma pretreatment means includes a plasma supply means and a magnetic forming means. The plasma pretreatment means cooperates with the plasma pretreatment roller 30 to confine oxygen plasma P near the surface of the substrate film S.

The plasma pretreatment means is provided so as to cover a portion of the pretreatment roller 30. Specifically, the plasma supply means and magnetic field forming means constituting the plasma pretreatment means are disposed along the surface near the outer periphery of the pretreatment roller 30, and are installed so as to form a gap sandwiched between the pretreatment roller 30, plasma supply nozzles 32a to 32c which supply plasma raw material gas and also serve as electrodes for generating plasma P, and magnetic field forming means having magnets 31 or the like for promoting the generation of plasma P.
As a result, plasma supply nozzles 32a to 32c are opened in the space of the gap to spray plasma toward the substrate surface, making the gap a plasma formation region, and further forming a region of high plasma density in the vicinity of the pretreatment roller 30 and the surface of the substrate film S, thereby enabling oxygen plasma pretreatment to be performed to form a plasma-treated surface on one side of the substrate film S.

The plasma supply means of the plasma pretreatment means includes a raw material volatilization supply device 28 connected to a plasma supply nozzle provided outside the decompression chamber 22, and a raw material gas supply line that supplies raw material gas from the device. The plasma raw material gas to be supplied is oxygen alone or a mixed gas of oxygen gas and an inert gas, which is supplied from a gas storage section through a flow controller while the gas flow rate is measured. The inert gas may be one or more mixed gases selected from the group consisting of argon, helium, and nitrogen. When a mixed gas of oxygen gas and an inert gas is used as the plasma raw material gas, it is preferable to use a mixed gas in which the oxygen partial pressure is higher than the inert gas partial pressure, from the viewpoint of normal adhesion and water-resistant adhesion between the substrate film and the aluminum oxide vapor deposition film.

These gases are mixed at a predetermined ratio as necessary to form a plasma raw material gas alone or a mixed gas for plasma formation, which is then supplied to the plasma supply means. The single gas or mixed gas is supplied to the plasma supply nozzles 32a to 32c of the plasma supply means, and is supplied to the vicinity of the outer periphery of the pretreatment roller 30 where the supply ports of the plasma supply nozzles 32a to 32c open.
The nozzle opening is directed toward the substrate film S on the pretreatment roller 30, and is arranged and configured to enable the oxygen plasma P to be uniformly diffused and supplied to the entire surface of the substrate film S, thereby enabling uniform plasma pretreatment of a large area of the substrate film S.

In the oxygen plasma pretreatment to obtain a conversion rate in the transition region of the aluminum oxide vapor deposition film, the mixture ratio of oxygen gas to the inert gas, that is, oxygen gas/inert gas, is preferably 1/1 to 6/1, and more preferably 3/2.5 to 3/1.
By setting the mixture ratio to 1/1 to 6/1, the film formation energy of the evaporated aluminum on the substrate film increases, and by setting the mixture ratio to 3/2.5 to 3/1, aluminum hydroxide is formed near the interface of the substrate, i.e., the transformation rate of the transition region decreases. Furthermore, by setting the mixture ratio to 3/2.5 to 3/1, the plasma discharge can be stabilized.

The plasma supply nozzles 32a to 32c function as opposing electrodes for the pretreatment roller 30 and are designed to have an electrode function. The plasma raw material gas supplied is excited by the potential difference caused by the high-frequency voltage, low-frequency voltage, etc. supplied between the nozzles and the pretreatment roller 30, generating and supplying plasma P.

Specifically, the plasma supply means of the plasma pretreatment means has a plasma pretreatment roller as a plasma power source, applies an AC voltage with a frequency of 10 Hz to 2.5 GHz between the opposing electrode, and performs input power control or impedance control, etc., to enable any voltage to be applied between the plasma pretreatment roller 30. The plasma supply means is provided with a power source 42 that can apply a bias voltage to make the oxygen plasma P, which can be used to physically or chemically modify the surface properties of the substrate, a positive potential.
The plasma intensity per unit area employed in the present invention is 50 to 8000 W·sec/m2; if it is less than ⁵⁰ W·sec/m2, the effect of the plasma pretreatment is not observed, and if it exceeds 8000 W·sec/ ^m2 , the substrate tends to be deteriorated by the plasma, such as wear, damage, coloring, and baking. In particular, the plasma intensity of the oxygen plasma pretreatment is preferably 100 to 500 W·sec/ ^m2 in order to achieve a transformation rate in the transition region of the aluminum oxide vapor deposition film. By applying the above plasma intensity with a bias voltage perpendicular to the substrate film, the normal adhesion and water-resistant adhesion to the aluminum oxide vapor deposition film are stably strengthened compared to conventional methods.

The plasma pretreatment means has a magnetic field forming means, which is provided with an insulating spacer and a base plate in a magnet case, and a magnet 31 is provided on the base plate. An insulating shield plate is provided on the magnet case, and an electrode is attached to the insulating shield plate.
Therefore, the magnet case and the electrodes are electrically insulated, and even if the magnet case is installed and fixed in the decompression chamber 22, the electrodes can be kept at an electrically floating level.

A power supply wiring 41 is connected to the electrodes, and the power supply wiring 41 is connected to a power source 42. Furthermore, a temperature adjustment medium pipe for cooling the electrodes and the magnet 31 is provided inside the electrodes.
The magnet 31 is provided so that oxygen plasma P from plasma supply nozzles 32a to 32c, which serve as electrodes and plasma supply means, can be concentrated and applied to the substrate film S. By providing the magnet 31, reactivity in the vicinity of the substrate surface is increased, making it possible to form a good plasma pre-treated surface at high speed.

The magnet 31 has a magnetic flux density of 10 to 10,000 gauss at the surface of the base film S. If the magnetic flux density at the surface of the base film S is 10 gauss or more, it is possible to sufficiently increase the reactivity near the base surface, and a good pre-treated surface can be formed at high speed.

The arrangement of the magnets 31 of the electrode causes the ions and electrons formed during plasma pretreatment to move in accordance with this arrangement. Therefore, even when plasma pretreatment is performed on a substrate film S having a large area of, for example, 1 ^m2 or more, the electrons, ions, and substrate decomposition products are uniformly diffused over the entire electrode surface, making it possible to perform the desired uniform and stable pretreatment with the desired plasma intensity, even when the substrate film S has a large area.

Next, the substrate film S that has been treated with the special oxidation plasma is moved from the substrate transport chamber 22A to the deposition chamber 22C by guide rolls 24a to 24d to guide it to the next deposition chamber 22C, where an aluminum oxide deposition film is formed in the deposition section. The deposition of the aluminum oxide deposition film is described below.

The film forming chamber 22C is placed under reduced pressure, and the substrate film S, which has been pretreated in the plasma pretreatment device, is wound around and transported with the treated surface of the substrate film S facing outward, and a film forming roller 33 for film forming processing and a target of a film forming source 34 arranged opposite the film forming roller are evaporated to form a vapor deposition film on the surface of the substrate film.
The vapor deposition film forming means 34 is of a resistance heating type, and uses an aluminum metal wire as an aluminum evaporation source. While supplying oxygen to oxidize the aluminum vapor, an aluminum oxide vapor deposition film is formed on the surface of the substrate film S.

In one embodiment, multiple aluminum metal wires are placed in a boat-shaped (referred to as a "boat type") deposition vessel in the axial direction of the roller 33 and heated by resistance heating. In this way, the aluminum metal material can be evaporated while reducing the amount of heat supplied, and an aluminum oxide deposition film can be formed while minimizing the thermal deformation of the substrate film S.

In one embodiment, in applications for packaging materials in which high-speed retort treatment of contents is performed, it is particularly preferred to perform oxygen plasma pretreatment with a mixture ratio of oxygen gas and inert gas of 3/2.5 to 3/1, a pretreatment pressure of 1 to 20 Pa, and a plasma intensity of 100 to 500 W·sec/ ^m2 , and further to set the thickness of the inorganic oxide vapor deposition layer to 9 to 14 nm. This can further improve the normal state adhesion and water-resistant adhesion at the interface between the substrate layer and the aluminum oxide vapor deposition film of the barrier film, and make the gas barrier property less susceptible to deterioration.

(Barrier Coat Layer)
The barrier coat layer constituting the barrier film according to the present invention is a layer having gas barrier properties, and is a cured film of a barrier coat composition containing a hydrolysis product of an alkoxysilane and a water-soluble polymer, and the barrier coat composition may further contain a silane coupling agent. In the present invention, by adjusting the ratio of silicon atoms to carbon atoms (Si/C) measured by X-ray photoelectron spectroscopy (XPS) on the surface of the barrier coat layer to 1.0 or more and 2.5 or less, excellent barrier performance can be achieved. If the Si/C is less than 1.0, in the cured film of the barrier coat composition containing the hydrolysis product of an alkoxysilane and a water-soluble polymer, the ratio of the water-soluble polymer to the hydrolysis product of the alkoxysilane is high, so that the swelling deterioration of the water-soluble polymer cannot be suppressed by the dehydration condensate of the alkoxysilane by the wet heat sterilization treatment at 135°C for 40 minutes, and the water vapor barrier property may be deteriorated. In addition, if the Si/C exceeds 2.5, the ratio of the hydrolysis product of the alkoxysilane to the water-soluble polymer is high, so that the film becomes sparse and brittle, and there is a risk of cracking in the film or of poor barrier property.

In one aspect of the present invention, the ratio of silicon atoms to carbon atoms (Si/C) on the surface of the barrier coat layer, as measured by X-ray photoelectron spectroscopy (XPS), is adjusted to preferably 1.6 to 2.3, more preferably 1.7 to 2.2, thereby achieving excellent water vapor barrier properties even after moist heat sterilization (retort treatment) of the packaging material.

In another aspect of the present invention, the ratio of silicon atoms to carbon atoms (Si/C) on the surface of the barrier coat layer, as measured by X-ray photoelectron spectroscopy (XPS), is adjusted to preferably 1.0 or more and less than 1.6, more preferably 1.1 or more and 1.5 or less, thereby achieving excellent oxygen barrier properties even after a tensile test of the barrier film.

The barrier coat layer can be formed, for example, from the following gas barrier coating film.
The gas barrier coating film is a coating film that retains gas barrier properties even in a high-temperature, high-humidity environment, and comprises at least one alkoxysilane represented by the general formula R ¹ _n Si(OR ² ) _m (wherein, R ¹ and R ² represent an organic group having 1 to 8 carbon atoms, n represents an integer of 0 or more, m represents an integer of 1 to 4, and n+m is 4), a water-soluble polymer, and a barrier coat composition obtained by polycondensation by a sol-gel method in the presence of a sol-gel catalyst, an acid, water, and an organic solvent.

In the above general formula R ¹ _n Si(OR ² ) _m , R ¹ is an optionally branched alkyl group having 1 to 8 carbon atoms, preferably 1 to 5, and more preferably 1 to 4 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an i-butyl group, a sec-butyl group, a t-butyl group, an n-hexyl group, and an n-octyl group.

In the above general formula R ¹ _n Si(OR ² ) _m , R ² is an optionally branched alkyl group having 1 to 8 carbon atoms, more preferably 1 to 5, and particularly preferably 1 to 4 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, a sec-butyl group, etc. When multiple (OR ² ) groups are present in the same molecule, the (OR ² ) groups may be the same or different.

As the alkoxysilane represented by the above general formula R ¹ _n Si(OR ² ) _m , at least one of a partial hydrolysis product of an alkoxysilane and a hydrolysis condensation product of an alkoxysilane can be used. Furthermore, the partial hydrolysis product of the alkoxysilane is not limited to one in which all of the alkoxy groups are hydrolyzed, but may be one in which one or more are hydrolyzed, or a mixture thereof. Furthermore, as the hydrolysis condensation product, a dimer or higher of a partially hydrolyzed alkoxide, specifically a dimer to hexamer, may be used.

In the present invention, alkoxysilanes represented by the above general formula R ¹ _n Si(OR ² ) _m can be preferably used. Suitable alkoxysilanes include, for example, tetramethoxysilane Si(OCH ₃ ) ₄ , tetraethoxysilane Si(OC ₂ H ₅ ) ₄ , tetrapropoxysilane Si(OC ₃ H ₇ ) ₄ , tetrabutoxysilane Si(OC ₄ H ₉ ) ₄ , methyltrimethoxysilane CH ₃ Si(OCH ₃ ) ₃ , methyltriethoxysilane CH ₃ Si(OC ₂ H ₅ ) ₃ , dimethyldimethoxysilane (CH ₃ ) ₂ Si(OCH ₃ ) ₂ , dimethyldiethoxysilane (CH ₃ ) ₂ Si(OC ₂ H ₅ ) ₂ and the like. In the present invention, condensation polymers of these alkoxysilanes can also be used. Specifically, for example, polytetramethoxysilane, polytetramethoxysilane, etc. can be used.

The water-soluble polymer used in the present invention may be a polyvinyl alcohol resin or an ethylene-vinyl alcohol copolymer, either alone or in combination with an ethylene-vinyl alcohol copolymer. In the present invention, the use of a polyvinyl alcohol resin and/or an ethylene-vinyl alcohol copolymer can significantly improve physical properties such as gas barrier properties, water resistance, weather resistance, and the like.

As the polyvinyl alcohol-based resin, generally, one obtained by saponifying polyvinyl acetate can be used. The polyvinyl alcohol-based resin may be a partially saponified polyvinyl alcohol-based resin in which several tens of percent of acetate groups remain, a fully saponified polyvinyl alcohol in which no acetate groups remain, or a modified polyvinyl alcohol-based resin in which the OH groups have been modified, and is not particularly limited.

As the ethylene-vinyl alcohol copolymer, a saponified product of a copolymer of ethylene and vinyl acetate, i.e., a product obtained by saponifying an ethylene-vinyl acetate random copolymer, can be used. For example, it includes a partially saponified product in which several tens of mol % of acetate groups remain, to a completely saponified product in which only a few mol % of acetate groups remain, or in which no acetate groups remain, and is not particularly limited. However, from the viewpoint of gas barrier properties, it is preferable to use a saponification degree of 80 mol % or more, more preferably 90 mol % or more, and even more preferably 95 mol % or more. The content of repeating units derived from ethylene in the ethylene-vinyl alcohol copolymer (hereinafter also referred to as "ethylene content") is usually 0 to 50 mol %, preferably 20 to 45 mol %.

A silane coupling agent may also be added to the barrier coat composition. For example, a silane coupling agent having a reactive group such as an alkoxy group such as a methoxy group or an ethoxy group, an acetoxy group, an amino group, or an epoxy group can be used. More specifically, examples of the silane coupling agent include 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropylmethyltriethoxysilane.

Furthermore, examples of the organic solvent that can be used in the barrier coat composition include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, and n-butanol. The polyvinyl alcohol resin and/or ethylene-vinyl alcohol copolymer are preferably handled in a dissolved state in a coating liquid containing the alkoxide and silane coupling agent, and the organic solvent can be appropriately selected from the organic solvents listed above. For example, when a polyvinyl alcohol resin and an ethylene-vinyl alcohol copolymer are used in combination, it is preferable to use n-butanol.

The barrier coat layer can be produced by the following method. First, the above alkoxysilane, water-soluble polymer, and optionally a silane coupling agent, a sol-gel catalyst, an acid, water, an organic solvent, etc. are mixed to prepare a barrier coat composition (barrier coat liquid).

Next, the barrier coat composition is applied onto the first inorganic oxide vapor deposition layer. The barrier coat composition can be applied by a coating means such as roll coating using a gravure roll coater, spray coating, spin coating, dipping, brushing, bar coding, applicator, etc., in one or multiple applications to form a coating film.

Next, the film coated with the barrier coat composition is heated and dried at a temperature of 20°C to 200°C and below the melting point of the vapor deposition film, preferably at a temperature in the range of 50°C to 180°C, for 3 seconds to 10 minutes. This allows polycondensation to occur, forming a barrier coat layer. Alternatively, the barrier coat composition may be coated on top of the first inorganic oxide vapor deposition layer to form two or more layers of coating film, and then heated and dried for 3 seconds to 10 minutes at a temperature of 20°C to 200°C and below the melting point of the resin substrate to form a composite polymer layer in which two or more gas barrier coating films are layered. This allows one or more barrier coat layers to be formed using the barrier coat composition.

The thickness of the barrier coat layer is preferably 10 to 5000 nm, more preferably 50 to 1000 nm, and even more preferably 100 to 500 nm. If the thickness of the barrier coat layer is within the above range, it can cover the surface of the deposited film without cracking.

<Packaging materials>
The packaging material according to the present invention comprises a heat seal layer, an intermediate layer, and a barrier layer made of the above-mentioned barrier film in this order. Since the packaging material of the present invention has such a layer structure, the gas barrier property is unlikely to deteriorate even after moist heat sterilization. Therefore, the packaging material of the present invention can be suitably used as a packaging material for retort packaged products that require gas barrier property even after moist heat sterilization.

The layer structure of the packaging material of the present invention will be described with reference to the drawings. The packaging material 50 shown in FIG. 4 comprises, in order from the outermost layer side, a substrate layer 52 (outermost layer), an inorganic oxide deposition layer 53, and a barrier layer 51 (barrier film) having a barrier coat layer 54, and on the barrier coat layer 54 side (inner side) of the barrier layer 51, an intermediate layer 55 and a heat seal layer 56 (innermost layer) are provided in this order. In addition, adhesive layers (not shown) may be present between the barrier coat layer 54 and the intermediate layer 55, and between the intermediate layer 55 and the heat seal layer 56.

The packaging material has an oxygen transmission rate of preferably 0.50 cc/ ^m2 ·atm·day or less, more preferably 0.25 cc/m2·atm·day or less, and even more preferably 0.20 cc/ ^m2 ·atm·day or less, measured in accordance with JIS K7126 under an environment of 23°C and 90% RH after moist heat sterilization treatment at ¹³⁵ °C for 40 minutes. If the oxygen transmission rate after moist heat sterilization treatment satisfies the above numerical range, the packaging material has suitable oxygen barrier properties, and therefore adverse effects on the contents of the packaging material can be suppressed even in retort packaged products.

The packaging material has a water vapor permeability measured in accordance with JIS K7129 under an environment of a temperature of 40° C. and a humidity of 100% RH after moist heat sterilization at 135° C. for 40 minutes of preferably 1.20 g/m ² ·day or less, more preferably 1.00 g/m ² ·day or less, even more preferably 0.70 g/m ² ·day or less, even more preferably 0.50 g/m ² ·day or less, and particularly preferably 0.40 g/m ² ·day or less. If the water vapor permeability after moist heat sterilization satisfies the above numerical range, the packaging material has suitable water vapor barrier properties, and therefore adverse effects on the contents of the packaging material can be suppressed even in retort packaged products.

The packaging material including the barrier film that has been pretreated with the special oxygen plasma has a normal peel strength between the base layer and the aluminum oxide vapor deposition film, measured in accordance with JIS K6854-2 after moist heat sterilization at 135°C for 40 minutes, of preferably 1.0 N or more, more preferably 2.0 N or more. The normal peel strength in the present invention is measured by the following method.

As a tensile tester, a Tensilon universal material testing machine manufactured by Orientec Co., Ltd. is used. First, as shown in FIG. 5, for example, a rectangular test piece 60 is prepared in a state in which the base layer 52 side and the heat seal layer 56 side (for example, the inorganic oxide deposition layer 53, the barrier coat layer 54, the intermediate layer 55, and the heat seal layer 56) are peeled off by 15 mm in the long side direction. The width (length of the short side) of the test piece 60 is 15 mm. Then, as shown in FIG. 6, the already peeled parts of the base layer 52 side and the heat seal layer 56 side are gripped by the gripper 61 and the gripper 62 of the measuring device, respectively. In addition, the grippers 61 and 62 are pulled at a speed of 50 mm/min in a direction perpendicular to the surface direction of the part where the base layer 52 side and the heat seal layer 56 side are still laminated (180° peeling: T-shaped peeling method), and the average value of the tensile stress in the stable region (see FIG. 7) is measured. When tension is started, the distance S between the grippers 61 and 62 is 30 mm, and when tension is stopped, the distance S between the grippers 61 and 62 is 60 mm. Figure 7 is a diagram showing the change in tensile stress with respect to the distance S between the grippers 61 and 62. As shown in Figure 7, the change in tensile stress with respect to the distance S passes through a first region and enters a second region (stable region) where the rate of change is smaller than that of the first region. The average value of the tensile stress in the stable region is measured, and this value is taken as the peel strength between the substrate layer of the barrier film and the aluminum oxide vapor deposition film.

The packaging material including the barrier film that has been pretreated with the special oxygen plasma has a water-exfoliation peel strength between the base layer and the aluminum oxide vapor-deposited film, measured in accordance with JIS K6854-2 after moist heat sterilization at 135°C for 40 minutes, of preferably 1.0 N or more, more preferably 2.0 N or more. The water-exfoliation peel strength in the present invention is measured by the following method.

Water-exposed peel strength is measured in the same manner as that for measuring normal peel strength, except for the points described below. In measuring water-exposed peel strength, the base layer side and heat seal layer side of the test piece are peeled off by 15 mm, and the peel strength of the adhesive interface between the base layer side and the heat seal layer side is measured. In measuring water-exposed peel strength, water is dropped with a dropper onto the boundary between the part where the base layer side and the heat seal layer side remain joined and the part where the base layer side and the heat seal layer side have been peeled off, when viewed along the longitudinal direction of the test piece.

Each layer constituting the packaging material of the present invention will be described below. Note that the barrier layer in the packaging material is the barrier film already described in detail, so a detailed description of it will be omitted here.

(Middle class)
In the packaging material of the present invention, various resin layers or resin films can be used as an intermediate layer for imparting durability, flex resistance, etc. to the packaging material. For example, a polyester-based resin, a polyolefin-based resin, or a polyamide-based resin can be used as the intermediate layer, and it is preferable to use a polyamide-based resin. Examples of polyamide resins include nylons such as polycaproamide (nylon 6), poly-ω-aminoheptanoic acid (nylon 7), poly-9-aminononanoic acid (nylon 9), polyundecaneamide (nylon 11), polylaurinlactam (nylon 12), polyethylenediamineadipamide (nylon 2,6), polytetramethyleneadipamide (nylon 4,6), polyhexamethylenediadipamide (nylon 6,6), polyhexamethylenesebacamide (nylon 6,10), polyhexamethylenedodecamamide (nylon 6,12), polyoctamethyleneadipamide (nylon 8,6), polydecamethyleneadipamide (nylon 10,6), polydecamethylenesebacamide (nylon 10,10), polydodecamethylenedodecamamide (nylon 12,12), and metaxylenediamine-6 nylon (MXD6). In addition, nylon 6-6,6, which is a copolymer of nylon 6 and nylon 6,6, nylon 6-12, which is a copolymer of nylon 6 and nylon 6-12, and the like can also be used. By using these nylons, it is possible to impart flex resistance to the packaging material. The method for forming the intermediate layer is not particularly limited, and the intermediate layer can be formed by a conventionally known method. For example, the intermediate layer may be formed by extrusion molding of a resin, or a resin film may be used.

The thickness of the intermediate layer is not particularly limited, but is preferably about 5 μm to 100 μm, and more preferably about 10 μm to 50 μm.

(Heat seal layer)
In the packaging material of the present invention, a thermoplastic resin can be used as the heat seal layer. Specifically, examples of the thermoplastic resin include low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, ethylene-α-olefin copolymers polymerized using a metallocene catalyst, polypropylene, ethylene-vinyl acetate copolymers, ionomer resins, ethylene-acrylic acid copolymers, ethylene-ethyl acrylate copolymers, ethylene-methacrylic acid copolymers, ethylene-methyl methacrylate copolymers, ethylene-propylene copolymers, methylpentene polymers, polybutene polymers, polyolefin resins such as polyethylene or polypropylene, acid-modified polyolefin resins obtained by modifying these polyolefin resins with unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, and itaconic acid, polyvinyl acetate resins, poly(meth)acrylic resins, and polyvinyl chloride resins.

The heat seal layer can be formed by melt-extruding one or more of the above-mentioned thermoplastic resins using an extruder or the like onto the intermediate layer, optionally via an anchor coat layer or the like. Alternatively, the heat seal layer can be formed by previously producing a film or sheet of the above-mentioned thermoplastic resin using one or more of the above-mentioned thermoplastic resins, and then dry laminating the produced film or sheet onto the intermediate layer via a lamination adhesive layer or the like.

To obtain desired properties, the above resins can be blended with other resins. In addition, various additives, such as antioxidants, UV absorbers, antistatic agents, antiblocking agents, lubricants (fatty acid amides, etc.), flame retardants, inorganic or organic fillers, dyes, pigments, etc., can be added as desired.

The thickness of the heat seal layer is not particularly limited, but to prevent poor sealing, it is preferably about 10 μm to 300 μm, and more preferably about 20 μm to 100 μm.

(Adhesive Layer)
In the packaging material of the present invention, the packaging material may further include an adhesive layer between the barrier layer and the intermediate layer, and between the intermediate layer and the heat seal layer. Examples of the adhesive layer include an adhesive resin layer and an adhesive layer. By including the adhesive layer in the packaging material, the laminate strength at the interface between each layer can be improved.

Thermoplastic resins that can be used for the adhesive resin layer include polyethylene-based resins, polypropylene-based resins, or cyclic polyolefin-based resins, or copolymer resins, modified resins, or mixtures (including alloys) that contain these resins as the main components. Examples of polyolefin resins include low density polyethylene (LDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), linear low density polyethylene (LLDPE), polypropylene (PP), ethylene-α-olefin copolymers polymerized using a metallocene catalyst, random or block copolymers of ethylene and polypropylene, ethylene-vinyl acetate copolymer (EVA), ethylene-acrylic acid copolymer (EAA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methacrylic acid copolymer (EMAA), ethylene-methyl methacrylate copolymer (EMMA), ethylene-maleic acid copolymer, ionomer resins, and acid-modified polyolefin resins obtained by modifying the above-mentioned polyolefin resins with unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, and itaconic acid in order to improve adhesion between layers. In addition, resins obtained by graft-polymerizing or copolymerizing unsaturated carboxylic acids, unsaturated carboxylic anhydrides, and ester monomers with polyolefin resins can be used. These materials can be used alone or in combination of two or more. Examples of cyclic polyolefin resins that can be used include cyclic polyolefins such as ethylene-propylene copolymers, polymethylpentene, polybutene, and polynorbornene. These resins can be used alone or in combination of two or more.

The adhesive may be, for example, a one-component or two-component curable or non-curable vinyl, (meth)acrylic, polyamide, polyester, polyether, polyurethane, epoxy, rubber, or other solvent, water-based, or emulsion adhesive. The above-mentioned laminating adhesive may be applied to the coating surface of the layer constituting the barrier laminate by, for example, a direct gravure roll coating method, a gravure roll coating method, a kiss coating method, a reverse roll coating method, a Fontaine method, a transfer roll coating method, or other methods. The amount of application is preferably 0.1 g/ ^m2 or more and 10 g/ ^m2 or less (dry state), and more preferably 1 g/ ^m2 or more and 5 g/ ^m2 or less (dry state).

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

<<Experiment I>>
<Manufacture of Barrier Films and Packaging Materials>
[Example 1-1]
A 12 μm-thick biaxially stretched polyethylene terephthalate film (hereinafter, PET film) was prepared as a substrate layer. The surface of the PET film on which the inorganic oxide vapor deposition layer was to be formed was subjected to plasma pretreatment, and then a 12 nm-thick aluminum oxide vapor deposition film (inorganic oxide vapor deposition layer) was formed on the plasma-treated surface using a reactive resistance heating method as a heating means for a vacuum vapor deposition method under the following conditions.
(Aluminum oxide film formation conditions)
Degree of vacuum: 8.1×10 ⁻² Pa

In addition, a hydrolysis solution of composition B, which had been prepared in advance, was added to the mixed solution of composition A prepared according to the composition shown in Table 1 and stirred to obtain a colorless and transparent barrier coat composition. Note that the values in Table 1 refer to parts by mass.

Next, the barrier coat composition prepared above was coated onto the aluminum oxide vapor deposition film of the PET film by the direct gravure method. After that, it was heated at 150°C for 60 seconds to form a barrier coat layer with a thickness of 300 nm (in a dry state), and further heated at 55°C for 72 hours to obtain a barrier film.

Next, a nylon film (thickness 15 μm) was laminated on the barrier coat layer of the barrier film obtained above via an adhesive. Furthermore, a non-axially oriented polypropylene film (CPP, thickness 70 μm) was laminated on the nylon film via an adhesive to obtain a packaging material (layer structure: substrate layer/aluminum oxide vapor deposition film/barrier coat layer/nylon film (intermediate layer)/CPP film (sealant layer)).

[Example 1-2]
A barrier film was obtained in the same manner as in Example 1-1, except that the composition of the barrier coat composition was changed to the formulation shown in Table 1.

Next, the barrier film obtained above was used to obtain a packaging material in the same manner as in Example 1-1.

[Examples 1-3]
A barrier film was obtained in the same manner as in Example 1-1, except that the composition of the barrier coat composition was changed to the formulation shown in Table 1.

Next, the barrier film obtained above was used to obtain a packaging material in the same manner as in Example 1-1.

[Examples 1 to 4]
A barrier film was obtained in the same manner as in Example 1-1, except that the composition of the barrier coat composition was changed to the formulation shown in Table 1.

Next, the barrier film obtained above was used to obtain a packaging material in the same manner as in Example 1-1.

[Examples 1 to 5]
A barrier film was obtained in the same manner as in Example 1-1, except that the composition of the barrier coat composition was changed to the formulation shown in Table 1.

Next, the barrier film obtained above was used to obtain a packaging material in the same manner as in Example 1-1.

[Examples 1 to 6]
A barrier film was obtained in the same manner as in Example 1-1, except that the composition of the barrier coat composition was changed to the formulation shown in Table 1.

Next, the barrier film obtained above was used to obtain a packaging material in the same manner as in Example 1-1.

[Comparative Example 1-1]
A barrier film was obtained in the same manner as in Example 1-1, except that the composition of the barrier coat composition was changed to the formulation shown in Table 1.

Next, the barrier film obtained above was used to obtain a packaging material in the same manner as in Example 1-1.

[Comparative Example 1-2]
A barrier film was obtained in the same manner as in Example 1-1, except that the composition of the gas barrier composition was changed to the formulation shown in Table 1.

Next, the barrier film obtained above was used to obtain a packaging material in the same manner as in Example 1-1.

<Performance evaluation of barrier film>
The barrier films produced in the above Examples 1-1 to 1-6 and Comparative Examples 1-1 and 1-2 were subjected to the following measurements.

(Elemental analysis of the barrier coat layer surface)
For the barrier films produced in the above Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-2, the ratio of Si element to C element present on the barrier coat layer surface was measured by narrow scan analysis under the following measurement conditions using X-ray photoelectron spectroscopy (XPS). The measurement results are shown in Table 2.
[Measurement condition]
Equipment used: "ESCA-3400" (Kratos) (Shimadzu Corporation)
[1] Spectrum collection conditions Incident X-ray: MgKα (monochromatic X-ray, hν = 1486.6 eV)
X-ray output: 150W (10kV, 15mA)
Measurement area: 6 mmφ
Photoelectron capture angle: 90 degrees [2] Ion sputtering conditions Ion species: Ar ⁺
Acceleration voltage: 0.2 (kV)
Emission current: 20 (mA)
Etch range: 10mmφ
Ion sputtering time (*): 30 seconds + 30 seconds + 60 seconds (total 120 seconds) was performed, and the spectrum was collected.

(Oxygen permeability measurement)
The barrier films produced in the above Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-2 were set so that the oxygen supply side was the base layer surface of the barrier film, and the oxygen permeability (cc/ ^m2 ·day) was measured in accordance with JIS K7126 under the measurement conditions of 23° C. and 90% RH using an oxygen permeability measuring device (manufactured by Modern Control (MOCON) [model name: OX-TRAN 2/21]). The measurement results are shown in Table 2.

(Measurement of oxygen permeability after tensile test)
The barrier films produced in the above Examples 1-1 to 1-2 and Comparative Examples 1-1 to 1-2 were cut to 200 (mm) x 100 (mm), and a metal ruler (TZ-1341, manufactured by KOKUYO) with a double-sided tape (No. 766 #40, manufactured by Teraoka Seisakusho) attached thereto was attached to the untreated surface side so that the distance between the metal rules was 150 mm.
Next, using a tensile testing machine (manufactured by Shimadzu Corporation [model: AG-X]), the sample was chucked so that the chuck distance was 150 mm and stretched 2% from the original dimension at a test speed of 10 m/min to create a sample.
The oxygen permeability (cc/ ^m2 ·day) of the obtained sample was measured in the same manner as above. The measurement results are shown in Table 2.

(Measurement of water vapor permeability)
For the barrier films produced in the above Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-2, the water vapor permeability (g/m2·day) was measured using a water vapor permeability measuring device (a measuring device manufactured by MOCON [model name: PERMATRAN ^3/33 ]) under the measurement conditions of 40° C. and 100% RH in accordance with JIS K7129, with the barrier films set so that the sensor side faced the base layer side of the barrier films. The measurement results are shown in Table 2.

<Performance evaluation of packaging materials>
The packaging materials produced in the above Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-2 were molded into bags (volume: 500 ml), filled with 200 ml of water, sealed, and then subjected to moist heat sterilization treatment for 40 minutes at 135° C. Then, a part of the bag was cut out to obtain a test sample, and the following measurements were performed.

(Oxygen permeability measurement)
The above test samples were set so that the oxygen supply side was the sealant layer (CPP film) side of the test sample using an oxygen transmission rate measuring device (manufactured by Modern Control (MOCON) [model name: OX-TRAN 2/21]), and the oxygen transmission rate (cc/ ^m2 ·atm·day) was measured in accordance with JIS K7126 under measurement conditions of 23°C and 90% RH atmosphere. The measurement results are shown in Table 2.

(Measurement of water vapor permeability)
The test samples were set so that the sensor side faced the sealant layer (CPP film) side of the test sample, and the water vapor permeability (g/m2·day) was measured in accordance with JIS K7129 under the measurement conditions of 40° C. and 100% RH atmosphere using a water vapor permeability measuring device (MOCON measuring device [model name: ^{PERMATRAN 3/33} ]). The measurement results are shown in Table 2.

From the results in Table 2, it can be seen that a barrier film having a barrier coat layer in which the ratio of silicon atoms to carbon atoms (Si/C) measured by XPS is 1.0 or more and 2.5 or less exhibits good barrier properties even after moist heat sterilization treatment (retort treatment).
In particular, in Examples 1-3 to 1-6, the state in which the barrier properties of the packaging material were taken into account was maintained after moist heat sterilization (retort treatment), and the water vapor barrier properties were better than those of the barrier film alone. In particular, in Examples 1-3 to 1-5, the water vapor barrier properties of the packaging material after moist heat sterilization (retort treatment) were extremely good.
Furthermore, in Examples 1-1 and 1-2, the barrier fills exhibited excellent oxygen barrier properties even after the tensile test.

<<Experiment II>>
[Example 2-1]
<Formation of Aluminum Oxide Vapor Deposition Film>
First, a roll of a 12 μm-thick PET film derived from fossil fuels was prepared as a base layer.
Next, a continuous vapor deposition film formation apparatus in which a pretreatment section in which an oxygen plasma pretreatment device was placed was separated from a film formation section was used on the surface of the PET film on which the inorganic oxide vapor deposition layer was to be formed. In the pretreatment section, plasma was introduced from a plasma supply nozzle under the conditions described below, and oxygen plasma pretreatment was performed at a transport speed of 400 m/min. In the film formation section, which was continuously transported, an aluminum oxide vapor deposition film (inorganic oxide vapor deposition layer) having a thickness of 12 nm was formed on the oxygen plasma-treated surface on the PET film using a reactive resistance heating method as the heating means for the vacuum vapor deposition method under the conditions described below.
(Oxygen plasma pretreatment conditions)
Plasma intensity: 200 W·sec/ ^m2
Plasma formation gas ratio: oxygen/argon = 2/1
Voltage applied between pretreatment drum and plasma supply nozzle: 340 V
Pretreatment pressure: 3.8 Pa
(Aluminum oxide film formation conditions)
Degree of vacuum: 8.1×10 ⁻² Pa
Conveying speed: 400 m/min
Oxygen gas supply amount: 20,000 sccm

<Formation of Barrier Coat Layer>
385 g of water, 67 g of isopropyl alcohol, and 9.1 g of 0.5N hydrochloric acid were mixed and adjusted to a pH of 2.2. 175 g of tetraethoxysilane as a metal alkoxide and 9.2 g of 3-glycidoxypropyltrimethoxysilane as a silane coupling agent were mixed into the solution while cooling to 10° C., to prepare solution C.
Solution D was prepared by mixing 14.7 g of polyvinyl alcohol having a polymerization degree of 2,400 and a saponification degree of 99% or more as a water-soluble polymer, 324 g of water, and 17 g of isopropyl alcohol.
The solution obtained by mixing the solutions C and D in a weight ratio of 6.5:3.5 was used as a barrier coat composition.
The above prepared barrier coat composition was coated on the aluminum oxide vapor deposition film of the above PET film by spin coating.
Thereafter, the film was heated in an oven at 180° C. for 60 seconds to form a barrier coat layer having a thickness of about 400 nm on the aluminum oxide vapor-deposited film, thereby obtaining a barrier film.

[Example 2-2]
A barrier film was obtained in the same manner as in Example 2-1, except that in the oxygen plasma pretreatment, the plasma intensity was changed to 100 W·sec/ ^m2.

[Example 2-3]
A barrier film was obtained in the same manner as in Example 2-1, except that a 12 μm-thick biomass-derived PET film was used as the base layer, and the plasma intensity was changed to 150 W·sec/ ^m2 in the oxygen plasma pretreatment.
The biomass-derived PET film was obtained by the following method.

83 parts by mass of terephthalic acid and 62 parts by mass of biomass ethylene glycol (manufactured by India Glycol) were fed as a slurry to a reaction vessel, and an esterification reaction was carried out at 240°C for 5 hours by a conventional direct polymerization method. Then, 0.013 parts by mass of trimethyl phosphate (manufactured by Aldrich) was added (15 mmol% relative to the acid component), and the mixture was then transferred to a polymerization reaction under high-temperature vacuum conditions. First, the vacuum degree was raised to 4000 Pa and the polymerization temperature to 280°C in 40 minutes, and then the vacuum degree was lowered to 200 Pa while maintaining the polymerization temperature at 280°C to carry out a melt polymerization reaction. The reaction time was 3 hours. The synthesized polymer was discharged in the form of a strand into running water and pelletized by a pelletizer. The pellets were dried at 160°C for 5 hours, and then solid-phase polymerized at 205°C under a nitrogen atmosphere and a vacuum of 50 Pa to obtain a polymer with an intrinsic viscosity of 0.8 dl/g. The intrinsic viscosity was calculated from the melt viscosity measured at 35°C using a phenol/tetrachloroethane (component ratio: 3/2) solvent. Differential thermal analysis of the obtained polymer (apparatus: Shimadzu DSC-60, measurement conditions: in helium gas, heating at 6°C/min) showed a glass transition temperature of 69°C, which was equivalent to that of known polyethylene terephthalate obtained from raw materials derived from fossil fuels. Radiocarbon measurement of the obtained biomass-derived polyethylene terephthalate was also performed, and the biomass degree as measured by radiocarbon (C14) was 31.25%.
Then, 60 parts by mass of the obtained polyethylene terephthalate, 30 parts by mass of recycled PET (lost parts during the manufacturing process such as ear loss during film formation were repelletized), and 10 parts by mass of a fossil fuel-derived polyethylene terephthalate master batch containing 200 ppm of porous silica having an average particle size of 0.9 μm as a lubricant were dried and fed to an extruder, melted at 285 ° C., extruded into a sheet from a T-die, and cooled and solidified with a cooling roll to obtain an unstretched sheet. Then, this unstretched sheet was stretched at a ratio of 3.5 times in the longitudinal direction with a low-speed driving roll speed of 6.5 m / min and a high-speed driving roll speed of 22 m / min, and further stretched at a ratio of 3.5 times in the transverse direction with a tenter to obtain a biaxially stretched PET film (biomass degree: 18.8%) having a thickness of 12 μm.

[Example 2-4]
A barrier film was obtained in the same manner as in Example 2-1, except that a 12 μm-thick polybutylene terephthalate film (hereinafter, PBT film) derived from fossil fuels was used as the base layer, the thickness of the aluminum oxide vapor deposition film was changed to 10 nm, and the plasma intensity in the oxygen plasma pretreatment was changed to 150 W·sec/ ^m2 .

[Example 2-5]
A barrier film was obtained in the same manner as in Example 2-1, except that a 12 μm-thick PET film derived from fossil fuels, whose moisture content had increased due to long-term storage under high humidity, was used, and the thickness of the aluminum oxide vapor-deposited film was changed by 14 nm.

[Example 2-6]
A barrier film was obtained in the same manner as in Example 2-1, except that the thickness of the aluminum oxide vapor-deposited film was changed by 10 nm.

[Example 2-7]
A barrier film was obtained in the same manner as in Example 2-1, except that the thickness of the aluminum oxide vapor deposition film was changed by 14 nm.

[Example 2-8]
A barrier film was obtained in the same manner as in Example 2-3, except that the thickness of the aluminum oxide vapor deposition film was changed by 10 nm.

[Example 2-9]
A barrier film was obtained in the same manner as in Example 2-3, except that the thickness of the aluminum oxide vapor deposition film was changed by 14 nm.

[Example 2-10]
A barrier film was obtained in the same manner as in Example 2-1, except that the oxygen plasma pretreatment was not performed.

[Comparative Example 2-1]
In the oxygen plasma pretreatment, the oxygen plasma pretreatment was performed in the same manner as in Example 2-1, except that the plasma formation gas ratio was oxygen/argon = 4/1. The plasma discharge was not stable, and the oxygen plasma pretreatment could not be performed.

[Comparative Example 2-2]
In the oxygen plasma pretreatment, the oxygen plasma pretreatment was performed in the same manner as in Example 2-1, except that the pretreatment pressure was set to 50 Pa. The plasma discharge was not stable, and the oxygen plasma pretreatment could not be performed.

[Reference Example 2-1]
In the oxygen plasma pretreatment, the oxygen plasma pretreatment was performed in the same manner as in Example 2-1, except that the plasma intensity was set to 1200 W·sec/m ^2. The PET film was colored.

The conditions for Examples 2-1 to 2-10, Comparative Examples 2-1 to 2-2, and Reference Example 2-1 are shown in Table 3.

<Measurement method for evaluation items>
The barrier films produced under the conditions shown in Examples 2-1 to 2-10 were used as samples for measurement, and elemental analysis of the barrier coat layer surface, conversion rate of the transition region of the evaporated film, oxygen permeability, water vapor permeability, and adhesion were measured using the following methods. The evaluation results are shown in Table 4.
In addition, the color of Example 2-1 and Reference Example 2-1 in which the PET film was colored were measured. The evaluation results are shown in Table 5.
For Comparative Examples 2-1 and 2-2, the oxygen plasma pretreatment could not be performed, and therefore the above evaluation items were not measured.

(Elemental analysis of the barrier coat layer surface)
The ratio of Si element to C element present on the barrier coat layer surface of the barrier film was measured by narrow scan analysis under the following measurement conditions using X-ray photoelectron spectroscopy (XPS).
[Measurement condition]
Equipment used: "ESCA-3400" (Kratos) (Shimadzu Corporation)
[1] Spectrum collection conditions Incident X-ray: MgKα (monochromatic X-ray, hν = 1486.6 eV)
X-ray output: 150W (10kV, 15mA)
Measurement area: 6 mmφ
Photoelectron capture angle: 90 degrees [2] Ion sputtering conditions Ion species: Ar ⁺
Acceleration voltage: 0.2 (kV)
Emission current: 20 (mA)
Etch range: 10mmφ
Ion sputtering time (*): 30 seconds + 30 seconds + 60 seconds (total 120 seconds) was performed, and the spectrum was collected.

(Metamorphic rate in the transition region)
The transformation rate of the transition region of the vapor-deposited film is obtained by repeatedly soft-etching the barrier coat layer surface of the barrier film at a constant rate with a Cs (cesium) ion gun while measuring ions derived from the barrier coat layer, ions derived from the inorganic oxide vapor-deposited layer, and ions derived from the base layer using time-of-flight secondary ion mass spectrometry (TOF-SIMS), to obtain the graph analysis diagram shown in Figure 2. Here, the unit of the vertical axis of the graph (intensity) is the intensity of the measured ions, and the unit of the horizontal axis (cycle) is the number of etching cycles.
The time-of-flight secondary ion mass spectrometer used in the TOF-SIMS was a TOF.SIMS5 manufactured by ION TOF, Inc., and the measurements were performed under the following measurement conditions.

(TOF-SIMS measurement conditions)
Primary ion type: _Bi3 ⁺⁺ (0.2 pA, 100 μs)
Measurement area: 150 x 150 ^μm2
Etching gun type: Cs (1 keV, 60 nA)
Etching area: 600 x 600 ^μm2
Etching rate: 3 sec/Cycle
In addition, in order to measure the ions derived from aluminum oxide, which is the target of measurement, it is necessary to select an ion gun that has sufficient strength to distinguish between the ions derived from aluminum oxide and ions derived from other components, and in particular to obtain a depth distribution that can be approximately converted into the concentration distribution of the _elemental bond _Al2O4H . Therefore, Cs ions were selected.

Using Cs, etch from the top surface of the barrier coat layer, analyze the element bond at the interface between the barrier coat layer, the aluminum oxide deposition film, and the base layer such as polyester film, and the element bond of the deposition film, and obtain the graphs of the measured elements and element bonds.In the graph, the position where the strength of _SiO2 (mass number 59.96), which is the constituent element of the barrier coat layer, is half that of the barrier coat layer is the interface between the barrier coat layer and the aluminum oxide deposition film, and the position where the strength of _C6 (mass number 72.00), which is the constituent material of the base layer, is half that of the layer part is the interface between the base layer and the aluminum oxide deposition film, and the part from the first interface to the second interface is the aluminum oxide deposition film.
Next, a peak is obtained in a graph representing the measured element bond Al ₂ O ₄ H (mass number 118.93), and the region from the peak to the interface is defined as a transition region, which can be obtained.
However, when the barrier coat layer is made of a material having the same mass number as Al ₂ O ₄ H (mass number 118.93), it is necessary to separate the waveform of 118.93.
In this case, the reactants _AlSiO4 and hydroxide _Al2O4H are generated at the interface between the barrier coat layer and the aluminum oxide vapor deposition film, so they are separated from _{the Al2O4H} present at the _film interface. This is done appropriately depending on the material of the barrier coat layer.
An example of a method for waveform separation is shown below: A profile of mass number 118.93 obtained by TOF-SIMS is subjected to nonlinear curve fitting using a Gaussian function, and overlapping peaks are separated using the least squares Levenberg Marquardt algorithm.
By carrying out the above operations, the transformation rate of the transition region of the aluminum oxide vapor-deposited film was calculated as (transition region thickness from the peak of elemental bond Al ₂ O ₄ H to the interface/aluminum oxide vapor-deposited film thickness)×100(%).

(Oxygen permeability measurement)
Using an oxygen permeability measuring device (manufactured by Modern Control (MOCON) [model name: OX-TRAN 2/21]), a packaging material prepared for the measurement was prepared as barrier film/adhesive/nylon film 15 μm/adhesive/CPP 70 μm, and the above test sample was set so that the oxygen supply side was the base layer surface of the barrier film, and measurement was performed in accordance with JIS K7126 Method B under measurement conditions of an atmosphere of 23° C. and 90% RH.
As a measurement sample,
1) Composite laminate film before retort treatment; 2) High retort treatment conditions: packaging material on one side of a bag of packaging material treated at 135°C for 40 minutes in a bag state; 3) Semi-retort treatment conditions: packaging material on one side of a bag of packaging material treated at 121°C for 40 minutes in a bag state was used.

(Measurement of water vapor permeability)
Using a water vapor permeability measuring device (a measuring device manufactured by MOCON [model name: PERMATRAN 3/33]), the above test sample was set so that the sensor side faced the substrate layer side of the barrier film, and measurement was performed in accordance with JIS K7126 Method B under measurement conditions of 40°C and 100% RH atmosphere.
As a measurement sample,
1) Packaging material before retort treatment; 2) High retort treatment conditions: Packaging material on one side of a bag of packaging material treated at 135°C for 40 minutes in a bag state; 3) Semi-retort treatment conditions: The packaging material on one side of a bag of packaging material treated at 121°C for 40 minutes in a bag state was used.

(Evaluation of adhesion between substrate layer and aluminum oxide vapor deposition film)
[Measurement of peel strength (1): Normal peel strength after retort treatment]
A two-component curing polyurethane adhesive was applied to the barrier coat layer side of the barrier film and dried, and then a film in which the two-component curing polyurethane adhesive and a 15 μm-thick stretched nylon film were attached to a 70 μm-thick unstretched polypropylene film was dry laminated to produce a packaging material.
100 mL of water was poured into a square pouch made to B5 size using the above packaging material, and hot water retort treatment (high retort treatment) was performed at 135°C for 40 minutes. After the retort treatment, the water in the contents of the square pouch was removed and cut into a 15 mm wide strip to prepare a sample. The peel strength between the base layer of the barrier film and the aluminum oxide vapor deposition film was measured for this sample using a tensile tester (manufactured by Orientec Co., Ltd. [model name: Tensilon universal material testing machine]) in accordance with JIS K6854-2. Note that, for Example 2-4, hot water retort treatment (semi-retort treatment) was performed at 121°C for 40 minutes.
For the measurement, a rectangular test piece was prepared in a state in which the base layer side and the non-stretched polypropylene film side were peeled off by 15 mm in the long side direction. Then, the already peeled parts of the base layer side and the non-stretched polypropylene film side were gripped by the gripper and gripper of the measuring device, respectively. In addition, the grippers were pulled at a speed of 50 mm/min in opposite directions (180° peeling: T-shaped peeling method) in a direction perpendicular to the surface direction of the part where the base layer side and the non-stretched polypropylene film side are still laminated, and the average value of the tensile stress in the stable region was measured. The distance between the grippers when the pulling started was 30 mm, and the distance between the grippers when the pulling ended was 60 mm. The change in the tensile stress with respect to the distance passed through the first region and entered the second region (stable region) where the rate of change was smaller than that of the first region. The average value of the tensile stress in the stable region was measured, and the value was taken as the peel strength between the base layer of the barrier film and the aluminum oxide vapor deposition film.

[Measurement of peel strength (2): Water-soaked peel strength after retort treatment]
The water-exposed peel strength was measured by the same method as that for measuring the normal peel strength, except for the following points. In the measurement of the water-exposed peel strength, the base layer side and the non-stretched polypropylene film side of the test piece were peeled off by 15 mm, and the peel strength of the adhesive interface between the base layer side and the non-stretched polypropylene film side was measured. In the measurement of the water-exposed peel strength, when the peel strength was measured, water was dropped with a dropper onto the boundary between the part where the base layer side and the non-stretched polypropylene film side maintained their bonding and the part where the base layer side and the non-stretched polypropylene film side were peeled off when viewed along the longitudinal direction of the test piece.

(Color measurement)
Using a spectrophotometer (manufactured by Konica Minolta, Inc. [model name: CM-700d]), the L* value, a ^* value, and b ^* value in the L ^* a ^* b ^* color system of one measurement sample (substrate layer/aluminum oxide vapor deposition film/barrier ^coat layer) were measured.

As shown in Examples 2-1 to 2-9 in Table 4 above, the barrier films in which the conversion rate in the transition region of the aluminum oxide vapor-deposited film was 5% or more and 60% or less exhibited good oxygen permeability and water vapor permeability even after retort treatment, and also showed good normal adhesion and water-resistant adhesion.
In the above Table 4, in Example 2-10, the peak of the element bond Al ₂ O ₄ H was too small to be separated and was hidden on the interface side of the base material layer, so that the transformation rate of the transition region could not be calculated (a value of 0% or less). Although Example 2-10 was inferior to Examples 2-1 to 2-9 in normal adhesion and water-resistant adhesion after retort, no deterioration in barrier property was observed before and after retort treatment.
Furthermore, in Table 5 above, since the b ^* value of Example 2-1 is lower than that of Reference Example 2-1, it is understood that Example 2-1 is more excellent in transparency than Reference Example 2-1.

11 Barrier film 12 Substrate layer 13 Inorganic oxide deposition layer 14 Barrier coat layer S Substrate film P Plasma 20 Roller-type continuous deposition film forming apparatus 22 Decompression chamber 22A Substrate transport chamber 22B Plasma pretreatment chamber 22C Film formation chamber 24a-d Guide roll 28 Raw material gas volatilization supply device 30 Pretreatment roller 31 Magnet 32a-d Plasma supply nozzle 33 Film formation roller 34 Deposition film formation means 41 Power supply wiring 42 Power sources 45a-45c Partition wall 50 Packaging material 51 Barrier layer (barrier film)
52 Base layer 53 Inorganic oxide deposition layer 54 Barrier coat layer 55 Intermediate layer 56 Heat seal layer 60 Test piece 61, 62 Grip

Claims (15)

A method for producing a barrier film comprising a barrier coat layer, an inorganic oxide vapor deposition layer, and a substrate layer in this order, comprising:
the barrier coat layer is a cured film of a barrier coat composition containing a hydrolysis product of an alkoxysilane and a water-soluble polymer,
the water-soluble polymer is a polyvinyl alcohol resin and/or an ethylene-vinyl alcohol copolymer,
the surface of the barrier coat layer has a ratio of silicon atoms to carbon atoms (Si/C) measured by X-ray photoelectron spectroscopy (XPS) of 1.0 or more and 2.5 or less;
the inorganic oxide vapor-deposited layer is an aluminum oxide vapor-deposited film,
The base layer is a polyethylene terephthalate film,
The manufacturing method includes a step of performing a plasma pretreatment on a surface of the base layer on which the inorganic oxide deposition layer is to be formed, using a mixed gas of oxygen gas and an inert gas;
The plasma intensity of the plasma pretreatment is 100 W·sec/m2 ^or more and 500 W·sec/m2 ^or less,
A mixing ratio of the oxygen gas to the inert gas (oxygen gas/inert gas) is 3 / 2.5 or more and 3/1 or less;
The method for producing a barrier film, wherein the pretreatment pressure of the plasma pretreatment is 1 Pa or more and 20 Pa or less. The method for producing a barrier film according to claim 1, wherein the surface of the barrier coat layer has a ratio of silicon atoms to carbon atoms (Si/C) measured by X-ray photoelectron spectroscopy (XPS) of 1.6 or more and 2.3 or less. The method for producing a barrier film according to claim 1, wherein the surface of the barrier coat layer has a ratio of silicon atoms to carbon atoms (Si/C) measured by X-ray photoelectron spectroscopy (XPS) of 1.0 or more and less than 1.6. The method for producing a barrier film according to any one of claims 1 to 3, wherein the barrier coat composition further contains a silane coupling agent. The method for producing a barrier film according to any one of claims 1 to 4, wherein the base layer is a biomass- derived polyethylene terephthalate film. a transition region is formed in the aluminum oxide vapor-deposited film, the transition region defining a peel strength between the surface of the base layer and the aluminum oxide vapor-deposited film;
the transition region contains elementally bound Al ₂ O ₄ H which transforms into aluminum hydroxide, as detected by etching using time-of-flight secondary ion mass spectrometry (TOF-SIMS);
The method for producing a barrier film according to any one of claims 1 to 5, wherein a transformation rate of a transition region, which is defined as a ratio of the transformed transition region to the aluminum oxide vapor-deposited film, determined by etching the barrier coat layer and the aluminum oxide vapor-deposited film using TOF-SIMS, is 5% or more and 60% or less. The method for producing a barrier film according to any one of claims 1 to 6, wherein the oxygen permeability of the barrier film measured in accordance with JIS K7126 under an environment of a temperature of 23°C and a humidity of 90% RH is 0.10 cc/ ^m2 ·atm·day or less. The method for producing a barrier film according to any one of claims 1 to 7, wherein the water vapor permeability of the barrier film measured in accordance with JIS K7129 under an environment of a temperature of 40°C and a humidity of 100% RH is 1.00 g/ ^m2 ·day or less. A method for producing a packaging material, comprising the steps of: producing a packaging material using the method for producing a barrier film according to any one of claims 1 to 8; The method for producing a packaging material according to claim 9, wherein the packaging material comprises, in this order, a heat seal layer, an intermediate layer, and a barrier layer made of the barrier film. The method for producing a packaging material according to claim 9 or 10, wherein the packaging material has an oxygen permeability of 0.50 cc/ ^m2 ·atm·day or less, measured in accordance with JIS K7126 under an environment of a temperature of 23°C and a humidity of 90% RH after moist heat sterilization at 135°C for 40 minutes. The method for producing a packaging material according to claim 9 or 10, wherein the water vapor permeability of the packaging material measured in accordance with JIS K7129 under an environment of a temperature of 40°C and a humidity of 100% RH after moist heat sterilization at 135°C for 40 minutes is 1.20 g/ ^m2 ·day or less. A method for producing a packaging material, comprising the steps of: producing a packaging material using the method for producing a barrier film according to any one of claims 1 to 8;
A method for producing a packaging material, wherein after the packaging material is subjected to a moist heat sterilization treatment at 135° C. for 40 minutes, the normal peel strength between the base material layer and the aluminum oxide vapor-deposited film measured in accordance with JIS K6854-2 is 1.0 N or more. A method for producing a packaging material, comprising the steps of: producing a packaging material using the method for producing a barrier film according to any one of claims 1 to 8;
A method for producing a packaging material, wherein after the packaging material is subjected to a moist heat sterilization treatment at 135° C. for 40 minutes, the water-sensitive peel strength between the base layer and the aluminum oxide vapor-deposited film measured in accordance with JIS K6854-2 is 1.0 N or more. The method for producing a packaging material according to any one of claims 9 to 14, wherein the packaging material is for a retort-packaged product.