JP2023028747A - gas barrier film - Google Patents

Abstract

To provide a gas barrier film having a small environmental load and an excellent gas barrier performance as a packaging material.SOLUTION: A gas barrier film has a substrate primarily composed of polyethylene, and a first gas barrier layer formed on a first face of the substrate. The maximum value of power spectrum density in a range of 1 μm-1 or more to 10 μm-1 or less in a spatial frequency obtained by atomic force microscopy in a range of 10 μm×10 μm on the first face of the substrate is 8.0 nm 3 or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to gas barrier films. The gas barrier film of the present invention is suitable for packaging foods, pharmaceuticals, precision electronic parts, and the like.

In packaging materials used for packaging food, pharmaceuticals, etc., from the viewpoint of suppressing deterioration of the contents and maintaining their functions and properties, blocking oxygen, water vapor, and other gases that deteriorate the contents that permeate the packaging materials. gas barrier properties that As a packaging material having gas barrier properties, there is known a gas barrier film using a metal foil such as aluminum, which is less affected by temperature and humidity, as a gas barrier layer.

As another structure of the gas barrier film, a film is known in which an inorganic oxide film such as silicon oxide or aluminum oxide is formed on a substrate film made of a polymeric material by vacuum deposition, sputtering, or the like. These gas barrier films have transparency and barrier properties against gases such as oxygen and water vapor. Moreover, as the base film, one made of polyethylene terephthalate (PET) is often used.

In recent years, due to the heightened environmental awareness stemming from the problem of marine plastic litter and the like, there has been a demand for further efficiency improvements in sorted collection and recycling of plastic litter. Therefore, there is an increasing demand for gas barrier films using base films made of polypropylene (PP) or polyethylene (PE).

JP 2020-055156 A

Patent document 1 also provides a laminate that uses polyethylene and is excellent in recyclability. However, the inventor's studies have revealed that a gas barrier film in which silicon oxide (SiOx) is simply formed as a barrier layer on a base film made of polyethylene does not have sufficient gas barrier performance.

In view of the above circumstances, it is an object of the present invention to provide a gas barrier film that has a low environmental load and excellent gas barrier performance as a packaging material.

The gas barrier film according to the present invention comprises a base material containing polyethylene as a main component, and a first gas barrier layer formed on the first surface of the base material. The maximum value of the power spectrum density is 8.0 nm ³ or less in the spatial frequency range of 1 μm ⁻¹ or more and 10 μm ⁻¹ or less obtained from atomic force microscope measurement of .

According to the present invention, it is possible to provide a gas barrier film that has a low environmental load and excellent gas barrier performance as a packaging material.

1 is a schematic cross-sectional view of a gas barrier film according to one embodiment of the present invention; FIG. 1 is a schematic cross-sectional view of a gas barrier film according to one embodiment of the present invention; FIG. 1 is a schematic cross-sectional view of a gas barrier film according to one embodiment of the present invention; FIG. Graph comparing power spectral densities

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. FIG. 1 to 3 are schematic cross-sectional views of a gas barrier film 1 according to this embodiment. The gas barrier film 1 includes a substrate 10 and a first gas barrier layer 30 formed on the first surface 10a of the substrate 10. As shown in FIG.

The base material 10 is a film having a resin whose main component is polyethylene. The thickness of the base material 10 is not particularly limited. The substrate 10 can be a single-layer film or a multilayer film in which films with different properties are laminated in consideration of the use of the packaging material. Considering workability when forming the first gas barrier layer 30 and the second gas barrier layer 40 described later, the thickness of the base material 10 is preferably in the range of 3 to 200 μm in practice, particularly 6 to 80 μm. is preferred.

The power spectrum density of the surface shape of the first surface 10a of the base material 10 can be obtained from measurement with an atomic force microscope (AFM), and the cross-sectional profile obtained by AFM is Fourier transformed and frequency analysis is performed. Power spectral densities at spatial frequencies can be calculated. The maximum value of the power spectral density in the spatial frequency range of 1 μm ⁻¹ or more and 10 μm ⁻¹ or less obtained from AFM measurement in the range of 10 μm×10 μm on the first surface 10 a of the substrate 10 is 8.0 nm ³ or less. preferable. By setting the surface shape of the first surface 10a within the above range, a dense film can be formed when the first gas barrier layer 30 is provided, and good gas barrier performance can be obtained.

Regardless of whether the substrate 10 is a single-layer film or a multilayer film, the polyethylene resin constituting the first surface 10a is high-density polyethylene (HDPE), low-density polyethylene (LDPE), or medium-density polyethylene. (MDPE), linear low-density polyethylene LLDPE, and ultra-low-density polyethylene, or a plurality thereof.

The substrate 10 may be either an unstretched film or a stretched film. When using a stretched film, there is no particular limitation on the stretch ratio. In addition, on the first surface 10a, the crystallinity calculated from the ratio of the crystal peak area to the total peak area measured by the parallel beam method of X-ray diffraction at a diffraction angle of 10° to 30° is 20% or more. may be

The base material 10 may contain additives other than resin components. The additive can be appropriately selected from various known additives. Examples of additives include antiblocking agents (AB agents), heat stabilizers, weather stabilizers, ultraviolet absorbers, lubricants, slip agents, nucleating agents, antistatic agents, antifogging agents, pigments, and dyes. The AB agent may be either organic or inorganic, but is preferably not added to the first surface 10a of the substrate 10 because it may adversely affect the formation of the gas barrier layer. Any one of these additives may be used alone, or two or more thereof may be used in combination. Among the above, lubricants and slip agents are preferable from the viewpoint of processability. The content of the additive in the base material 10 can be appropriately adjusted within a range that does not impair the effects of the present embodiment.

The first gas barrier layer 30 is a layer mainly composed of silicon oxide, silicon oxide containing carbon, silicon nitride, metal aluminum, or aluminum oxide, and has barrier properties against predetermined gases such as oxygen and water vapor. It is a layer that demonstrates The first gas barrier layer 30 may be transparent or opaque, and is provided on the first surface 10a side of the substrate 10 .

The thickness of the first gas barrier layer 30 varies depending on the type of component used, composition, and film formation method, but generally can be appropriately set within the range of 3 to 300 nm. If the thickness of the first gas barrier layer 30 is less than 3 nm, a uniform film may not be obtained or the film thickness may not be sufficient, and the function as a gas barrier layer may not be sufficiently exhibited. If the thickness of the first gas barrier layer 30 exceeds 300 nm, the first gas barrier layer 30 may crack due to external factors such as bending and pulling after film formation, resulting in loss of barrier properties. More preferably, the thickness of the first gas barrier layer 30 is in the range of 6 to 150 nm.

The method for forming the first gas barrier layer 30 is not limited, and for example, a vacuum deposition method, a plasma activated deposition method, an ion beam deposition method, an ion plating method, a sputtering method, a plasma-enhanced chemical vapor deposition (PECVD) method, or the like can be used. . By combining the plasma-assisted method and the ion-beam-assisted method, the first gas barrier layer 30 can be densely formed to improve the barrier property.

A pretreatment layer 20 may be provided before forming the first gas barrier layer 30 on the first surface 10a of the substrate 10 (FIG. 2). By providing the pretreatment layer 20, the film formability and adhesion strength of the first gas barrier layer 30 can be improved. There are no restrictions on the components and formation method of the pretreatment layer 20, and it can be selected from thermoplastic resins, thermosetting resins, ultraviolet curable resins, plasma treatment, and the like. , 10 μm×10 μm, the maximum value of the power spectral density in the spatial frequency range of 1 μm ⁻¹ to 10 μm ⁻¹ obtained by AFM measurement is preferably 8.0 nm ³ or less.

When a resin layer is used for the pretreatment layer 20, the content of the organic polymer in the pretreatment layer 20 may be, for example, 70% by mass or more, or may be 80% by mass or more. Examples of organic polymers include polyacrylic resins, polyester resins, polycarbonate resins, polyurethane resins, polyamide resins, polyolefin resins, polyimide resins, melamine resins, and phenol resins. Considering the strength, it is preferable to include at least one of polyacrylic resin, polyol resin, polyurethane resin, polyamide resin, or reaction product of these organic polymers. The pretreatment layer 20 may also contain a silane coupling agent, organic titanate, or modified silicone oil.

More preferably, the organic polymer used in the pretreatment layer 20 is an organic polymer having a urethane bond generated by a reaction between a polyol having two or more hydroxyl groups at the polymer end and an isocyanate compound, and/or a high Examples include organic polymers containing reaction products of polyols having two or more hydroxyl groups at the molecular ends and organic silane compounds such as silane coupling agents or hydrolysates thereof.

Examples of polyols include at least one selected from acrylic polyols, polyvinyl acetals, polystyrene polyols, polyurethane polyols, and the like. The acrylic polyol may be obtained by polymerizing an acrylic acid derivative monomer, or may be obtained by copolymerizing an acrylic acid derivative monomer and another monomer. Acrylic acid derivative monomers include ethyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, and hydroxybutyl methacrylate. Examples of monomers to be copolymerized with acrylic acid derivative monomers include styrene.

The isocyanate compound has the effect of increasing the adhesion between the base material 10 and the first gas barrier layer 30 through urethane bonds generated by reacting with polyol. That is, the isocyanate compound functions as a cross-linking agent or curing agent. Examples of isocyanate compounds include monomers such as aromatic tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), aliphatic xylene diisocyanate (XDI), hexamethylene diisocyanate (HMDI), and isophorone diisocyanate (IPDI). , polymers thereof, and derivatives thereof. The isocyanate compounds described above may be used singly or in combination of two or more.

Silane coupling agents include, for example, vinyltrimethoxysilane, γ-chloropropylmethyldimethoxysilane, γ-chloropropyltrimethoxysilane, glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and γ- methacryloxypropylmethyldimethoxysilane and the like. The organosilane compound may be a hydrolyzate of these silane coupling agents. The organic silane compound may contain one of the above-mentioned silane coupling agents and hydrolysates thereof alone or in combination of two or more thereof.

The resin layer provided as the pretreatment layer 20 is formed by mixing the above-described components in an organic solvent in an arbitrary ratio to prepare a mixed solution, and using the prepared mixed solution on the first surface 10a of the base material 10. be able to. The mixture includes, for example, tertiary amines, imidazole derivatives, carboxylic acid metal salt compounds, quaternary ammonium salts, quaternary phosphonium salts and other curing accelerators; phenolic, sulfur, and phosphite antioxidants; A leveling agent; a flow control agent; a catalyst; a cross-linking reaction accelerator;

The mixture is applied to the substrate 10 using a known printing method such as offset printing, gravure printing, or silk screen printing, or a known coating method such as roll coating, knife edge coating, or gravure coating. It can be coated on one side 10a. After coating, the pretreatment layer 20 can be formed by heating to, for example, 50 to 200° C. and drying and/or curing.

When a resin layer is formed as the pretreatment layer 20, the thickness may be adjusted according to the application or required properties, but is preferably 0.01 to 1 μm, more preferably 0.01 to 0.5 μm. If the thickness of the pretreatment layer 20 is 0.01 μm or more, sufficient adhesion strength between the base material 10 and the first gas barrier layer 30 can be obtained, and gas barrier properties are also improved. If the thickness of the pretreatment layer 20 is 1 μm or less, it is easy to form a uniform coating surface, and the drying load and manufacturing cost can be suppressed.

When the pretreatment layer 20 is formed by plasma treatment, in-line plasma treatment is preferable from the viewpoint of productivity. The plasma treatment method is not particularly limited to glow discharge or the like, and a magnet may be used to increase the plasma density. Gas used for plasma treatment can be selected from one or more of oxygen, nitrogen, and argon.

A second gas barrier layer 40 may be further provided on the first gas barrier layer 30 (on the side of the first surface 10a) (FIG. 3). The second gas barrier layer 40 protects the first gas barrier layer 30 and further enhances the barrier properties of the gas barrier film 1 . The second gas barrier layer 40 is made of a thermoplastic resin, a thermosetting resin, an ultraviolet curable resin, a metal alkoxide, a water-soluble polymer, a polycarboxylic acid polymer, a polyvalent metal compound, a polycarboxylic acid polymer and a polyvalent metal. Coating layers such as polyvalent metal salts of carboxylic acids that are reaction products with compounds can be used. Especially preferred are metal alkoxides and water-soluble polymers, which are excellent in oxygen barrier properties. This is formed using a coating agent containing an aqueous solution or a water/alcohol mixed solution containing a water-soluble polymer and at least one kind of metal alkoxide or a hydrolyzate thereof as a main ingredient. For example, a coating agent is prepared by dissolving a water-soluble polymer in an aqueous (water or water/alcohol mixed) solvent and mixing a metal alkoxide directly or a material that has been previously hydrolyzed. The second gas barrier layer 40 can be formed by applying this coating agent on the first gas barrier layer 30 and then drying it.

Each component contained in the coating agent for forming the second gas barrier layer 40 will be described in more detail. Examples of water-soluble polymers used in coating agents include polyvinyl alcohol (PVA), polyvinylpyrrolidone, starch, methylcellulose, carboxymethylcellulose, and sodium alginate. In particular, use of PVA is preferable because excellent gas barrier properties can be obtained. PVA is generally obtained by saponifying polyvinyl acetate. As the PVA, both so-called partially saponified PVA in which several tens of percent of acetic acid groups remain and complete PVA in which only several percent of acetic acid groups remain can be used. A PVA intermediate between the two may be used.

The metal alkoxide used in the coating agent is a compound represented by the general formula M(OR) _n (M: metal of Si and Al, R: alkyl group such as CH ₃ and C ₂ H ₅ ). Specific examples include tetraethoxysilane [Si(OC ₂ H ₅ ) ₄ ], triisopropoxyaluminum Al[OCH(CH ₃ ) ₂ ] ₃ and the like. Silane coupling agents include those having an epoxy group such as 3-glycidoxypropyltrimethoxysilane, those having an amino group such as 3-aminopropyltrimethoxysilane, and mercapto groups such as 3-mercaptopropyltrimethoxysilane. , those having an isocyanate group such as 3-isocyanatopropyltriethoxysilane, and tris-(3-trimethoxysilylpropyl)isocyanurate.

A polycarboxylic acid-based polymer is a polymer having two or more carboxy groups in its molecule. Examples of polycarboxylic acid-based polymers include (co)polymers of ethylenically unsaturated carboxylic acids; copolymers of ethylenically unsaturated carboxylic acids and other ethylenically unsaturated monomers; alginic acid, carboxymethyl cellulose and acidic polysaccharides having a carboxyl group in the molecule such as pectin. Examples of ethylenically unsaturated carboxylic acids include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid and the like. Ethylenically unsaturated monomers copolymerizable with ethylenically unsaturated carboxylic acids include, for example, ethylene, propylene, saturated carboxylic acid vinyl esters such as vinyl acetate, alkyl acrylates, alkyl methacrylates, and alkyl itaconates. , vinyl chloride, vinylidene chloride, styrene, acrylamide, acrylonitrile and the like. These polycarboxylic acid-based polymers may be used singly or in combination of two or more.

From the viewpoint of gas barrier properties, a structure derived from at least one polymerizable monomer selected from the group consisting of acrylic acid, maleic acid, methacrylic acid, itaconic acid, fumaric acid and crotonic acid among the above components. Polymers containing units are preferred, and polymers containing structural units derived from at least one polymerizable monomer selected from the group consisting of acrylic acid, maleic acid, methacrylic acid and itaconic acid are particularly preferred. In the above polymer, the proportion of structural units derived from at least one polymerizable monomer selected from the group consisting of acrylic acid, maleic acid, methacrylic acid and itaconic acid is preferably 80 mol% or more, It is more preferably 90 mol % or more (provided that the total of all structural units constituting the polymer is 100 mol %). This polymer may be a homopolymer or a copolymer. When the polymer is a copolymer containing structural units other than the above structural units, the other structural units include, for example, ethylenically unsaturated monomers copolymerizable with the aforementioned ethylenically unsaturated carboxylic acids. Structural units derived from and the like.

The number average molecular weight of the polycarboxylic acid polymer is preferably in the range of 2,000 to 10,000,000, more preferably 5,000 to 1,000,000. If the number average molecular weight is less than 2,000, the water resistance of the gas barrier film may be insufficient depending on the application, and moisture may deteriorate the gas barrier properties and transparency, or cause whitening. On the other hand, if the number-average molecular weight exceeds 10,000,000, the viscosity of the coating agent increases, which may impair the coatability. In the present embodiment, the number average molecular weight is the polystyrene-equivalent number average molecular weight determined by gel permeation chromatography (GPC).

Various additives can be added to the coating agent mainly composed of polycarboxylic acid polymer. Inhibitors, dispersants, surfactants, softeners, stabilizers, film formers, thickeners, and the like.

An aqueous medium is preferable as the solvent used for the coating agent containing a polycarboxylic acid-based polymer as a main component. Aqueous media include water, water-soluble or hydrophilic organic solvents, or mixtures thereof. The aqueous medium usually contains water or water as a main component. The content of water in the aqueous medium is preferably 70% by mass or more, more preferably 80% by mass or more. Examples of water-soluble or hydrophilic organic solvents include alcohols such as methanol, ethanol and isopropanol, ketones such as acetone and methyl ethyl ketone, ethers such as tetrahydrofuran, cellosolves, carbitols, and nitriles such as acetonitriles. is mentioned.

The polyvalent metal compound is not particularly limited as long as it is a compound that reacts with the carboxyl groups of the polycarboxylic acid-based polymer to form a polyvalent metal salt of polycarboxylic acid, such as zinc oxide particles, magnesium oxide particles, magnesium methoxide. , copper oxide, calcium carbonate, and the like. These may be used singly or in combination. From the viewpoint of the oxygen barrier properties of the oxygen barrier coating, zinc oxide particles are preferred among the above. Zinc oxide is an inorganic material that has the ability to absorb ultraviolet light. Although the average particle size of the zinc oxide particles is not particularly limited, the average particle size is preferably 5 μm or less, more preferably 1 μm or less, and 0.1 μm or less from the viewpoint of gas barrier properties, transparency, and coatability. is particularly preferred.

When a coating agent containing a polyvalent metal compound as a main component is applied and dried to form a film, various additives may be added in addition to zinc oxide particles, if necessary, as long as the effects of the present embodiment are not impaired. may contain. Examples of the additive include a resin soluble or dispersible in the solvent used for the coating agent, a dispersant soluble or dispersible in the solvent, a surfactant, a softening agent, a stabilizer, a film-forming agent, a thickener, and the like. may contain. Among the above, it is preferable to contain a resin that is soluble or dispersible in the solvent used for the coating agent. This improves the coatability and film formability of the coating agent. Examples of such resins include alkyd resins, melamine resins, acrylic resins, urethane resins, polyester resins, phenol resins, amino resins, fluorine resins, epoxy resins, and isocyanate resins. Moreover, it is preferable to contain a dispersant that is soluble or dispersible in the solvent used for the coating agent. This improves the dispersibility of the polyvalent metal compound. As the dispersant, an anionic surfactant or a nonionic surfactant can be used. The surfactants include (poly)carboxylates, alkyl sulfates, alkylbenzenesulfonates, alkylnaphthalenesulfonates, alkylsulfosuccinates, alkyldiphenyletherdisulfonates, alkylphosphates, aromatic Phosphate ester, polyoxyethylene alkyl ether, polyoxyethylene alkylphenol ether, polyoxyethylene alkyl ester, alkylallyl sulfate, polyoxyethylene alkyl phosphate, sorbitan alkyl ester, glycerin fatty acid ester, sorbitan fatty acid ester, sucrose fatty acid various surfactants such as esters, polyethylene glycol fatty acid esters, polyoxyethylene sorbitan alkyl esters, polyoxyethylene alkyl allyl ethers, polyoxyethylene derivatives, polyoxyethylene sorbitol fatty acid esters, polyoxy fatty acid esters, polyoxyethylene alkylamines, etc. be done. These surfactants may be used alone or in combination of two or more. When the additive is contained in the coating agent containing the polyvalent metal compound as the main component, the mass ratio of the polyvalent metal compound and the additive (polyvalent metal compound: additive) is 30:70 to 99. :1, preferably 50:50 to 98:2.

Solvents used in coating agents containing polyvalent metal compounds as main components include, for example, water, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-propyl alcohol, n-butyl alcohol, n-pentyl alcohol, dimethylsulfoxide, Dimethylformamide, dimethylacetamide, toluene, hexane, heptane, cyclohexane, acetone, methyl ethyl ketone, diethyl ether, dioxane, tetrahydrofuran, ethyl acetate, butyl acetate. Moreover, these solvents may be used individually by 1 type, or may be used in mixture of 2 or more types. Among these, methyl alcohol, ethyl alcohol, isopropyl alcohol, toluene, ethyl acetate, methyl ethyl ketone, and water are preferred from the viewpoint of coatability. Moreover, from the viewpoint of manufacturability, methyl alcohol, ethyl alcohol, isopropyl alcohol, and water are preferred.

When forming a film of a polyvalent metal compound after applying and drying a coating agent containing a polycarboxylic acid-based polymer as a main component, the polycarboxylic acid-based polymer has a part of the carboxy group in advance. It may be neutralized with a basic compound. By partially neutralizing the carboxyl groups of the polycarboxylic acid polymer in advance, the water resistance and heat resistance of the film made of the polycarboxylic acid polymer can be further improved. As the basic compound, at least one basic compound selected from the group consisting of the above-described polyvalent metal compounds, monovalent metal compounds and ammonia is preferred. Examples of monovalent metal compounds include sodium hydroxide and potassium hydroxide.

When applying and drying a coating agent in which a polycarboxylic acid-based polymer and a polyvalent metal compound are mixed to form a film, the polycarboxylic acid-based polymer, the polyvalent metal compound, and water or an alcohol are used as a solvent. , a resin or dispersant that can be dissolved or dispersed in a solvent and, if necessary, additives are mixed to prepare a coating agent. The second gas barrier layer 40 can also be formed by applying and drying such a coating agent by a known coating method.

Examples of coating methods for the second gas barrier layer 40 include casting, dipping, roll coating, gravure coating, screen printing, reverse coating, spray coating, kit coating, die coating, and metering bar coating. , a chamber doctor combination coating method, a curtain coating method, and the like.

The thickness of the second gas barrier layer 40 varies depending on the composition of the coating agent used, the coating conditions, etc., and is not particularly limited. However, when the film thickness of the second gas barrier layer 40 after drying is less than 0.01 μm, a uniform coating film may not be obtained, and sufficient gas barrier properties may not be obtained. If the film thickness after drying exceeds 50 μm, the second gas barrier layer 40 is likely to crack. Therefore, the preferred thickness of the second gas barrier layer 40 is, for example, in the range of 0.01-50 μm. The optimum thickness of the second gas barrier layer 40 is, for example, in the range of 0.1-10 μm.

The gas barrier film 1 of the present embodiment having the above configuration exhibits high gas barrier properties, and the main resin component is polyethylene, and the ratio of the main resin component in the gas barrier film 1 is 90% by mass or more. is also easy. That is, the gas barrier film 1 can be configured as a highly recyclable monomaterial.

When a packaging material such as a packaging bag is produced using the gas barrier film 1, a heat-sealable heat-sealable layer 60 is further provided on the first gas barrier layer 30, and the heat-sealed layers are heat-sealed to each other. , packaging materials can be easily produced. In this case also, by making the main resin component of the heat seal layer 60 the same as the main resin component of the base material 10, the packaging material can be a monomaterial. When providing the second gas barrier layer 40 , the heat seal layer 60 may be provided on the second gas barrier layer 40 . Another layer may be provided between the heat seal layer 60 and the first gas barrier layer 30 or the second gas barrier layer 40 as appropriate.

By using the same polyethylene as the base material 10 as the material of the heat seal layer 60, recycling becomes possible. As the polyethylene resin used for the heat seal layer 60, it is preferable to use low-density polyethylene or linear low-density polyethylene because heat sealing is easy. The thickness of the heat seal layer 60 is determined depending on the purpose, and can be, for example, about 50 to 200 μm. The heat seal layer 60 is laminated on the first gas barrier layer 30 or the second gas barrier layer 40 via the adhesive layer 50 made of adhesive.

A known dry lamination adhesive can be used for the adhesive layer 50 . The dry lamination adhesive is not particularly limited, but specific examples include a two-liquid curing type ester-based adhesive, an ether-based adhesive, a urethane-based adhesive, and the like. Alternatively, the heat seal layer 60 may be laminated by extrusion lamination using a fluid resin.

A gas barrier adhesive can be used for the adhesive layer 50 . By applying the gas barrier adhesive to the adhesive layer 50, the gas barrier properties of the gas barrier film can be improved. The oxygen permeability of the gas barrier adhesive is preferably 150 cc/m ² ·day·atm or less, more preferably 100 cc/m ² ·day·atm or less, and 80 cc/m ² ·day·atm or less. is more preferably 50 cc/m ² ·day·atm or less. When the oxygen permeability is within the above range, the gas barrier properties of the laminate can be sufficiently improved, and even if a slight crack occurs in the first gas barrier layer 30 or the second gas barrier layer 40, However, the gap can be supplemented by the gas-barrier adhesive entering into the gap, and the deterioration of the gas-barrier property can be suppressed.

The gas-barrier adhesive may be any adhesive that exhibits gas-barrier properties after curing, and examples thereof include epoxy-based adhesives and polyester/polyurethane-based adhesives. As specific examples, "Maxieve" manufactured by Mitsubishi Gas Chemical Company, Ltd., "Paslim" manufactured by DIC Corporation, and the like can be used.

The thickness of the adhesive layer 50 is preferably 0.1 to 20 μm, more preferably 0.5 to 10 μm, even more preferably 1 to 5 μm. When the thickness of the gas barrier adhesive is equal to or greater than the above lower limit, cracking of the inorganic oxide 11 can be more sufficiently suppressed, and the gas barrier properties of the laminate can be further improved. In addition, since the thickness of the gas barrier adhesive is equal to or greater than the above lower limit, it is possible to obtain a cushioning property that mitigates impact from the outside, and it is possible to prevent cracking of the first gas barrier layer 30 due to the impact. On the other hand, when the thickness of the gas barrier adhesive is equal to or less than the above upper limit, there is a tendency that the flexibility of the gas barrier laminate can be sufficiently maintained.

In addition to the above conditions, it is particularly preferable that the thickness of the adhesive layer 50 is 50 times or more the thickness of the first gas barrier layer 30 . When the thickness of the adhesive layer 50 satisfies the above conditions, cracking of the first gas barrier layer 30 and the second gas barrier layer 40 can be more sufficiently suppressed, and the adhesive layer 50 is coated with a gas barrier adhesive. When used, the gas barrier properties of the gas barrier film 1 can be further improved. In addition, when the thickness of the adhesive layer 50 satisfies the above conditions, it is possible to further enhance the cushioning property of mitigating the impact from the outside, thereby preventing the first gas barrier layer 30 and the second gas barrier layer 40 from cracking due to the impact. can be prevented. On the other hand, the thickness of the adhesive layer 50 is preferably 300 times or less the thickness of the first gas barrier layer 30 from the viewpoints of maintaining the flexibility of the gas barrier film 1, processability, and cost.

Adhesives for forming the adhesive layer 50 can be used, for example, by bar coating, dipping, roll coating, gravure coating, reverse coating, air knife coating, comma coating, die coating, screen printing, and spraying. It can be applied by a coating method, a gravure offset method, or the like. The temperature for drying the coating film obtained by applying this adhesive can be, for example, 30 to 200.degree. C., preferably 50 to 180.degree. The temperature for curing the coating film can be, for example, room temperature (27°C) to 70°C, preferably 30 to 60°C. By setting the drying and curing temperatures within the above ranges, cracks in the first gas barrier layer 30 and the adhesive layer 50 can be further suppressed, and excellent gas barrier properties can be exhibited.

From the viewpoint of preventing the first gas barrier layer 30 from cracking, the adhesive layer 50 and the first gas barrier layer 30 are preferably in direct contact with each other. Therefore, the adhesive is preferably formed by coating the adhesive on the first gas barrier layer 30, drying and curing the adhesive.

A printed layer can be provided on the substrate 10 or the heat seal layer 60 . In general, the printed layer is provided at a position visible from the outside of the gas barrier film for the purpose of displaying information about the contents, identifying the contents, or improving the design of the packaging bag. The printing method and printing ink are not particularly limited, and are appropriately selected from known printing methods and printing inks in consideration of printability on film, design properties such as color tone, adhesion, safety as a food container, etc. be. Examples of printing methods that can be used include gravure printing, offset printing, gravure offset printing, flexographic printing, and inkjet printing. Among them, the gravure printing method can be preferably used from the viewpoint of productivity and high definition of the pattern. The printed layer may or may not be provided as appropriate depending on the intended use.

In order to improve the adhesion of the printed layer, the surface of the layer forming the printed layer may be subjected to various pretreatments such as corona treatment, plasma treatment and flame treatment, or may be provided with a coating layer such as an easy adhesion layer.

A printing base material may be attached as the second base material 70 to the second surface 10b side of the base material 10 opposite to the first surface 10a. By using the same polyethylene as the base material 10 as the material of the second base material 70, recycling becomes possible. The second surface 10b of the base material may be provided with various pretreatments such as corona treatment, plasma treatment, and flame treatment, or a coating layer such as an easy-adhesion layer, in order to improve adhesion with the second base material 70. I do not care. Dry lamination using a known dry lamination adhesive or extrusion lamination can be used. Specifically, the base material 10 and the second base material 70 can be adhered via the adhesive layer 50 described above.

The gas barrier film of this embodiment will be further described using examples and comparative examples. The present invention is not limited in any way by the specific contents of Examples and Comparative Examples.

(Example 1)
As the base material 10, a polyethylene film having a maximum power spectral density of 1.4 nm ³ in a spatial frequency range of 1 μm ⁻¹ or more and 10 μm ^{−1 or} less obtained from AFM measurement in a range of 10 μm × 10 μm on the first surface 10a ( thickness of 25 μm) was used. SiO was sublimated in a vacuum apparatus, and a first gas barrier layer 30 (thickness: 30 nm) made of silicon oxide (SiOx) was formed on the first surface of the substrate 10 by electron beam evaporation.

Subsequently, on the first gas barrier layer 30, as the adhesive layer 50, 23 parts by mass of a solvent obtained by mixing ethyl acetate and methanol at a mass ratio of 1:1 and 16 parts by mass of Maxieve C93T manufactured by Mitsubishi Gas Chemical Company, Inc. Adhesive A, which is an epoxy adhesive, was prepared by mixing 5 parts by mass of Maxieve M-100 manufactured by Mitsubishi Gas Chemical Co., Ltd. An LLDPE film MC-S (thickness: 60 μm) manufactured by Tohcello Co., Ltd. was laminated as the heat seal layer 60 with the adhesive A interposed therebetween.
As described above, the gas barrier film 1 according to Example 1 was produced.

(Example 2)
A gas barrier film 1 of Example 2 was produced in the same manner as in Example 1, except that the film thickness of the first gas barrier layer 30 made of silicon oxide (SiOx) was 14 nm.

(Example 3)
As the substrate 10, a polyethylene film having a maximum power spectral density of 4.2 nm ³ in a spatial frequency range of 1 μm ⁻¹ or more and 10 μm ^{−1 or} less obtained from AFM measurement in a range of 10 μm × 10 μm on the first surface 10a ( A gas barrier film 1 of Example 3 was produced in the same manner as in Example 1, except that a film having a thickness of 35 μm was used.

(Example 4)
A gas barrier film 1 of Example 4 was produced in the same manner as in Example 3, except that the film thickness of the first gas barrier layer 30 made of silicon oxide (SiOx) was set to 40 nm.

(Example 5)
Plasma treatment with Ar gas is performed on the first surface 10a of the base material 10 at a treatment intensity of 100 W·sec/m ² , and the spatial frequency obtained from AFM measurement in the range of 10 μm × 10 μm of the surface is 1 μm ⁻¹ or more. A pretreatment layer 20 having a maximum power spectral density of 3.8 nm ³ in the range of 10 μm ⁻¹ or less was formed.
The calculation of the treatment intensity is as follows.
Power density [W/m ² ] = input power [W] / cathode area [m ² ]
Processing time [sec] = Electrode MD width [m] / Processing speed [m/sec]
Processing intensity = Power density [W/m ² ] ・Processing time [sec]

After providing the pretreatment layer 20 under the above conditions, the first gas barrier layer 30 (thickness 25 nm) is provided in the same manner as in Example 1, and the adhesive A described in Example 1 (adhesive layer 50) is interposed therebetween. The gas barrier film 1 of Example 5 was produced by laminating it with the heat seal layer 60 .

(Example 6)
As the pretreatment layer 20 on the first surface 10a of the substrate 10, the maximum value of the power spectral density in the range of spatial frequencies 1 μm ⁻¹ to 10 μm ⁻¹ obtained from AFM measurement in the range of 10 μm × 10 μm on the surface is 2 A thermosetting resin layer of .1 nm ³ was provided.

The thermosetting resin layer is formed by mixing acrylic polyol and tolylene diisocyanate so that the number of NCO groups of tolylene diisocyanate is equal to the number of OH groups of acrylic polyol, and the total solid content (acrylic polyol and tolylene diisocyanate) was diluted with ethyl acetate to 5% by mass. β-(3,4 Epoxycyclohexyl)trimethoxysilane was further added to the mixed solution after dilution so as to be 5 parts by mass with respect to the total amount of 100 parts by mass of acrylic polyol and tolylene diisocyanate, and these were mixed. It was prepared by The thermosetting resin was applied to the first surface 10a by gravure coating, dried and cured to form a thermosetting resin layer. A gas barrier film 1 of Example 6 was produced in the same manner as in Example 5 except that the thermosetting resin layer was provided and the film thickness of the first gas barrier layer 30 was set to 28 nm.

(Example 7)
On the first gas barrier layer 30, a coating agent obtained by mixing the following liquids (1) and (2) at a weight ratio of 6:4 was applied by gravure coating and dried to form a second gas barrier layer having a thickness of 0.4 μm. 40 was formed, and a 60 μm-thick LLDPE film (as the heat seal layer 60) was laminated by dry lamination using a two-component curing type polyurethane adhesive, and the film thickness of the first gas barrier layer 30 was set to 30 nm. A gas barrier film 1 of Example 7 was produced in the same manner as in Example 6, except that
(1) Liquid: 89.6 g of hydrochloric acid (0.1N) was added to 10.4 g of tetraethoxysilane and stirred for 30 minutes to hydrolyze. 3 wt% water/isopropyl alcohol solution of alcohol (water: isopropyl alcohol weight ratio 90:10)

(Example 8)
A gas barrier film 1 of Example 8 was produced in the same manner as in Example 1, except that the first gas barrier layer 30 having a thickness of 3 nm was formed by electron beam evaporation of aluminum oxide (AlOx).

(Example 9)
A gas barrier film 1 of Example 9 was produced in the same manner as in Example 8, except that the film thickness of the first gas barrier layer 30 made of aluminum oxide (AlOx) was 6 nm.

(Example 10)
A gas barrier film 1 of Example 10 was produced in the same manner as in Example 3, except that the first gas barrier layer 30 having a thickness of 10 nm was formed by electron beam evaporation of aluminum oxide (AlOx).

(Example 11)
A gas barrier film 1 of Example 11 was produced in the same manner as in Example 6, except that the first gas barrier layer 30 having a thickness of 20 nm was formed by electron beam evaporation of aluminum oxide (AlOx).

(Example 12)
A gas barrier film 1 of Example 12 was produced in the same manner as in Example 1, except that the first gas barrier layer 30 having a thickness of 10 nm was formed by electron beam evaporation of metal aluminum (Al).

(Example 13)
Example 3 except that hexamethyldisiloxane (HMDSO) was introduced into the vacuum chamber and the first gas barrier layer 30 (thickness: 30 nm) made of carbon-containing silicon oxide (SiOxCy) was formed by plasma CVD. A gas barrier film of Example 13 was produced in the same manner.

(Example 14)
As the first gas barrier layer 30, monosilane ( _SiH.sub.4 ), ammonia ( _NH.sub.3 ), and nitrogen ( _N.sub.2 ) are introduced into a vacuum apparatus, and a gas barrier layer (thickness: 30 nm) made of silicon nitride (SiNx) is formed by plasma CVD. ) was formed in the same manner as in Example 3 to prepare a gas barrier film of Example 14.

(Comparative example 1)
As a substrate ^{, a} polyethylene film (thickness ³² μm ) was used to prepare a gas barrier film of Comparative Example 1 in the same manner as in Example 1.

(Comparative example 2)
As a base material, ^a polyethylene film ⁽ thickness 30 ^μm ) was used to prepare a gas barrier film of Comparative Example 2 in the same manner as in Example 1.

(Comparative Example 3)
A gas barrier film of Comparative Example 3 was produced in the same manner as in Comparative Example 1, except that aluminum oxide (AlOx) was deposited by electron beam evaporation to form a first gas barrier layer having a thickness of 10 nm.

Evaluation items and measurement methods in each example and comparative example are shown below.

(Power spectrum analysis of base material and pretreatment layer surface shape)
For the power spectrum analysis of the surface shape of the substrate and the pretreatment layer, an atomic force microscope (AFM5400L) manufactured by Hitachi High-Tech Science Co., Ltd. was used, and cross-sectional profile data (unit: nm) was obtained in the range of 10 μm×10 μm. In order to convert the obtained uneven waveform of the cross section into the spatial frequency domain, the spatial frequency component was decomposed by Fourier transform, and the power spectrum intensity at the spatial frequency included in each range was integrated for each unit spatial frequency width. Then, the obtained power spectrum intensity was divided by the number of data to calculate the power spectrum density, which is the power spectrum per unit spatial frequency. The formula for calculating the power spectral density is shown below.

Since the uneven waveform of the cross-sectional profile is an irregular variation and is a superimposition of waves of various spatial frequencies, it can be expressed by the following Fourier integral formula (1). The Fourier component X(f) represents the amplitude (in nm) of the wave e ^i2πft of frequency f.

The obtained Fourier component represents the magnitude and phase of the complex number component of each frequency component, and is expressed as a power value per unit spatial frequency width (1 μm ⁻¹ width) so as not to depend on the frequency resolution Δf of the Fourier transform. , the Fourier components are converted to energy (power) and compared. The frequency resolution Δf is represented by the following equation (2).
Δf=1/T=f _s /N (2)
In order to increase the frequency resolution (reduce Δf), either the sampling frequency fs is decreased or the number of sampling points N is increased.
A complex number Z obtained from the Fourier transform is expressed by the following equation (3) where a is a real number component, b is an imaginary number component, and A is a real number.
Z=a+bi=Ae ^iθ (3)
Therefore, the power spectrum can be represented by the absolute value of the complex number |Z|
Power spectrum A=|Z|=√a ² +b ² (4)
Then, in order to make this power spectrum a value per unit spatial frequency, the power spectrum was divided by the number of data to obtain a power spectrum density, which is a power spectrum per unit spatial frequency.

(Evaluation of gas barrier performance after coating layer formation)
Oxygen transmission rate (OTR) (unit: cc/m ² · day · atm, measurement conditions: 30 ° C.-70% RH) and water vapor transmission rate (WVTR) (unit: g / m ² ·day, measurement conditions: 40° C.-90% RH) were evaluated. OTR was measured using OX-TRAN2/22 manufactured by mocon, and WVTR was measured using PERMATRAN-W3/34 manufactured by mocon.

Table 1 shows the results of power spectrum analysis, gas barrier performance measurement, and evaluation.

In Examples 1 to 14, the maximum value of the power spectral density in the spatial frequency range of 1 μm ⁻¹ or more and 10 μm ⁻¹ or less obtained from AFM measurement in the range of 10 μm × 10 μm on the surface of the substrate 10 and the pretreatment layer 20 Since it was 8.0 nm ³ or less, sufficient gas barrier properties of OTR of 0.8 cc/m ² ·day·atm or less and WVTR of 0.9 g/m ² ·day or less could be confirmed.

In Comparative Examples 1 to 3, the maximum value of the power spectral density in the spatial frequency range of 1 μm ⁻¹ to 10 μm ⁻¹ obtained from AFM measurement in the range of 10 μm × 10 μm on the surface of the base material and the pretreatment layer is 8. 0 nm ³ , the oxygen barrier properties and/or water vapor barrier properties were inferior to those of Examples 1 to 14.

A comparison of power spectrum densities in Example 1 and Comparative Example 1 is shown in FIG.

An embodiment and an example of the present invention have been described above, but the specific configuration is not limited to this embodiment, and modifications and combinations of configurations without departing from the gist of the present invention are also included. .

INDUSTRIAL APPLICABILITY The gas barrier film of the present invention is highly recyclable as a polyethylene material and exhibits excellent gas barrier properties, so it can be suitably used mainly as a packaging material.

1 gas barrier film 10 substrate 10a first surface 10b second surface 20 pretreatment layer 30 first gas barrier layer 40 second gas barrier layer 50 adhesive 60 heat seal layer 70 second substrate

Claims (11)

Atomic force microscope measurement in an area of 10 μm × 10 μm on the first surface of the substrate comprising a substrate containing polyethylene as a main component and a first gas barrier layer formed on the first surface of the substrate A gas barrier film having a maximum power spectral density of 8.0 nm ³ or less in a spatial frequency range of 1 μm ⁻¹ or more and 10 μm ⁻¹ or less. 2. The gas barrier film according to claim 1, wherein the first surface of said base material is one of high density polyethylene, medium density polyethylene, low density polyethylene and ultra low density polyethylene. The first surface of the substrate is measured by the parallel beam method of X-ray diffraction at a diffraction angle of 10° to 30°, and the crystallinity calculated from the ratio of the crystal peak area to the total peak area is 20%. The gas barrier film according to claim 1 or 2, characterized by the above. 4. The gas barrier film according to any one of claims 1 to 3, wherein the first surface of the substrate is free of an anti-blocking agent. 5. The gas barrier film according to any one of claims 1 to 4, wherein the first gas barrier layer comprises one or more of silicon oxide, carbon-containing silicon oxide, silicon nitride, metal aluminum, and aluminum oxide. The first surface of the substrate has a pretreatment layer formed by a thermoplastic resin, a thermosetting resin, an ultraviolet curable resin, or a plasma treatment, and an atomic force in the range of 10 μm×10 μm on the surface of the pretreatment layer 6. The gas barrier according to any one of claims 1 to 5, wherein the maximum value of the power spectral density in the spatial frequency range of 1 μm ⁻¹ to 10 μm ⁻¹ obtained by microscopic measurement is 8.0 nm ³ or less. the film. A second gas barrier layer is further provided on the first gas barrier layer, and the second gas barrier layer is a layer composed of a metal alkoxide, a hydrolyzate of a metal alkoxide, a water-soluble polymer, a polycarboxylic acid-based polymer, or a multi-layer. 7. The gas barrier according to any one of claims 1 to 6, comprising a layer comprising either a valent metal compound or a polyvalent metal salt of a carboxylic acid that is a reaction product of a polycarboxylic acid polymer and a polyvalent metal compound. the film. The gas barrier film according to any one of claims 1 to 7, wherein a heat seal layer is laminated on the first gas barrier layer or the second gas barrier layer via an adhesive. 9. The gas barrier film according to claim 8, wherein said adhesive is a gas barrier adhesive. 10. The gas barrier film according to claim 8 or 9, wherein said heat seal layer is low density polyethylene or linear low density polyethylene. The gas barrier film according to any one of claims 1 to 10, wherein a second substrate containing polyethylene as a main component is laminated on the second surface of the substrate.

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