Laminated film and method for producing the same

Abstract

To provide a laminated film and a method for producing the laminated film that achieve further suppression of a decrease in gas barrier properties in a high-humidity environment.SOLUTION: A laminated film comprises a base material layer, a first layer laminated on at least one surface of the base material layer, and a second layer containing, as a main component, at least one selected from the group consisting of a metal and an inorganic oxide, wherein the base material layer contains a thermoplastic resin, the first layer contains, as a main component, a polyvinylidene chloride-based polymer, and the second layer is directly laminated on the first layer.

Description

[Technical Field]

[0001] The present disclosure relates to a laminated film and a method for producing the same. [Background technology]

[0002] Conventionally, gas barrier films have been known in which a laminated film having gas barrier properties is formed on a film serving as a base layer to suppress the permeation of oxygen, water vapor, etc. To further improve the gas barrier properties, laminated films have also been known in which a vapor-deposited layer of a metal or inorganic oxide is further provided on the laminated film having gas barrier properties.

[0003] For example, Patent Document 1 proposes that a multilayer substrate layer is formed by providing a resin material having a polar group as a coating layer on a stretched polypropylene resin layer, thereby improving the adhesion between the vapor-deposited film and the multilayer substrate layer and improving the gas barrier properties. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2021-024136 Summary of the Invention [Problem to be solved by the invention]

[0005] However, conventional laminated films having a vapor-deposited film of a metal or inorganic oxide have a problem in that the vapor-deposited film is easily deteriorated, particularly when stored in a high-humidity environment, resulting in a decrease in gas barrier properties.

[0006] An object of the present disclosure is to provide a laminated film that can further suppress the deterioration of gas barrier properties in a high-humidity environment, and a method for producing the same. [Means for solving the problem]

[0007] As a result of extensive research, the inventors of the present invention have found that: a substrate layer; a first layer laminated on at least one surface of the base material layer; a second layer containing at least one selected from a metal and an inorganic oxide as a main component; the substrate layer contains a thermoplastic resin, the first layer contains a polyvinylidene chloride polymer as a main component, It has been found that the above-mentioned problems can be solved by a laminated film in which the second layer is laminated directly on the first layer. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide a laminated film that can further suppress deterioration of gas barrier properties in a high-humidity environment, and a method for producing the same. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of the present disclosure will be described in detail below. However, the scope of the present disclosure is not limited to the embodiment described herein, and various modifications can be made without departing from the spirit of the present disclosure. Each aspect disclosed in this specification can be combined with any other feature disclosed in this specification. Furthermore, when multiple upper and lower limit values ​​are described for a particular parameter, any of these upper and lower limit values ​​can be combined to form a suitable numerical range. Furthermore, the lower and / or upper limit values ​​of a numerical range described in this disclosure are numerical values ​​within that numerical range and may be replaced with numerical values ​​shown in the examples. The expression "X to Y" indicating a numerical range means "X or more and Y or less." Furthermore, unless otherwise noted, all test temperatures were room temperature (20°C ± 5°C). When a particular description given for one embodiment is applicable to other embodiments, that description may be omitted in the other embodiments.

[0010] The configurations and combinations thereof in each embodiment are merely examples, and additions, omissions, substitutions, and other modifications of the configurations are possible as appropriate within the scope of the present disclosure. The present disclosure is not limited by the embodiments, but is limited only by the claims. Each feature disclosed herein may be combined with any other feature disclosed herein.

[0011] [Laminated film] A first embodiment of the present disclosure relates to a laminated film. The laminated film according to the first embodiment is a substrate layer; a first layer laminated on at least one surface of the base material layer; a second layer containing at least one selected from a metal and an inorganic oxide as a main component; the substrate layer contains a thermoplastic resin, the first layer contains a polyvinylidene chloride polymer as a main component, The second layer is laminated directly onto the first layer.

[0012] The laminated film according to the first embodiment can further suppress the deterioration of gas barrier properties in a high humidity environment. When a layer containing a metal or inorganic oxide is directly laminated on a base layer (herein also simply referred to as "base layer") made of a thermoplastic resin, pinholes are likely to occur in the layer containing the metal or inorganic oxide in a high-humidity environment, and the gas barrier properties are likely to deteriorate. Therefore, the present inventors have conducted extensive research and found that by providing a layer containing a polyvinylidene chloride polymer between the base layer and a layer containing at least one selected from a metal and an inorganic oxide (herein also referred to as "inorganic layer"), the deterioration of the gas barrier properties can be further suppressed even in a high-humidity environment. In general, it is known that polyvinylidene chloride polymers easily react with moisture in the air and generate trace amounts of hydrochloric acid over time. Therefore, it has been thought that if a layer containing a polyvinylidene chloride copolymer is directly laminated to an inorganic layer, the inorganic layer will easily deteriorate and the gas barrier properties will be reduced. For this reason, no laminate film in which a layer containing a polyvinylidene chloride polymer and an inorganic layer are directly laminated has been known to date. However, through intensive research, the present inventors have found that when a layer containing a polyvinylidene chloride polymer is provided between a substrate layer and an inorganic layer, the inorganic layer does not deteriorate even when the layer containing the polyvinylidene chloride polymer and the inorganic layer are directly laminated together, and that deterioration of the inorganic layer is actually more suppressed. This has resulted in a laminate film that can further suppress deterioration of gas barrier properties in high-humidity environments. In addition, this laminate film can also suppress changes in appearance over time in high-humidity environments. On the other hand, even when a layer containing a polyvinylidene chloride polymer is provided between the base layer and the inorganic layer, if the layer containing the polyvinylidene chloride polymer and the inorganic layer are not directly laminated together (for example, if another resin layer or adhesive layer is laminated between the layer containing the polyvinylidene chloride polymer and the inorganic layer), it has been found that the inorganic layer (especially the layer containing a metal) may be altered due to the generation of hydrochloric acid. In this case, it is difficult to prevent a decrease in gas barrier properties in a high-humidity environment.

[0013] <Base material layer> The substrate layer contains a thermoplastic resin, that is, the substrate layer is made of a resin composition containing a thermoplastic resin (hereinafter, sometimes referred to as a "substrate layer resin composition").

[0014] (thermoplastic resin) Examples of thermoplastic resins include polyolefin resins (polyethylene, polypropylene, etc.), polyester resins (polyethylene naphthalate, polyethylene terephthalate, etc.), polyamide resins (nylon-6, nylon-66, etc.), polystyrene, ethylene-vinyl alcohol copolymer resin, polyvinyl chloride, polyimide, polyvinyl alcohol, polycarbonate, polyethersulfone, acrylic resins, and cellulose resins (triacetyl cellulose, diacetyl cellulose, etc.). These thermoplastic resins may be used alone or in combination of two or more. In one embodiment, the thermoplastic resin is preferably a polyolefin-based resin, and the substrate layer is preferably a film made of a polyolefin-based resin.

[0015] Examples of polyolefin resins include polyethylene resins and polypropylene resins.

[0016] Examples of polyethylene resins include low-density polyethylene resin (LDPE), medium-density polyethylene resin (MDPE), linear low-density polyethylene resin (LLDPE), ethylene-vinyl acetate copolymer (EVA) resin, ethylene-α-olefin copolymer resin, and ethylene-(meth)acrylic acid copolymer resin.

[0017] The polypropylene-based resin may be, for example, a homopolypropylene resin, a block polypropylene resin, a random polypropylene resin, or a copolymer resin of propylene and another monomer. Examples of the other monomer include α-olefins such as ethylene, 1-butene, 1-hexene, 1-octene, 3-methylpentene, and 4-methylpentene. The polypropylene-based resin may also be a copolymer resin obtained by combining propylene with two or more other monomers. When the base layer contains the copolymer resin, it preferably contains 80% by mass or more of propylene as a monomer component, more preferably 90% by mass or more, more preferably 95% by mass or more, and particularly preferably 98% by mass or more.

[0018] Furthermore, the polypropylene resin may have an atactic structure, an isotactic structure, a syndiotactic structure, or a metallocene structure.

[0019] In one embodiment, the substrate layer is preferably a polypropylene-based resin film (particularly, a homopolypropylene film). This film may be a uniaxially stretched film, a biaxially stretched film, or an unstretched film. The substrate layer may be composed of a single-layer film or a laminate of two or more films. When the substrate layer is a laminate of two or more films, the types of polyolefin-based resins contained in the layers may be the same or different. In one embodiment, the substrate layer is preferably a biaxially oriented polypropylene (OPP) film.

[0020] The polyolefin resin contained in the substrate layer may be a biomass-derived polyolefin resin or a mechanically recycled or chemically recycled polyolefin resin.

[0021] (additives) The resin composition for the base layer may contain known additives such as antioxidants, weather stabilizers, heat stabilizers, lubricants, crystal nucleating agents, UV absorbers, colorants, and antiblocking agents, as long as the effects of the present disclosure are not impaired. For example, at least one resin selected from petroleum resins and terpene resins may be blended in to improve the water vapor barrier properties of the base layer. When the base layer contains these resins, the total content thereof may be 1% by mass or more, 2% by mass or more, 15% by mass or less, or 10% by mass or less, relative to the total mass of the resin composition for the base layer.

[0022] Furthermore, for the purpose of improving the adhesion between the substrate layer and the first layer, the surface of the substrate layer may be subjected to corona discharge treatment, plasma treatment, etc. If necessary, the surface on which the first layer is not laminated (the uncoated surface) may be subjected to corona discharge treatment or plasma treatment.

[0023] The thickness of the substrate layer is not particularly limited and can be appropriately set depending on the application of the packaging film. In one embodiment, the thickness of the substrate layer may be 5 μm or more, 10 μm or more, or 15 μm or more. The upper limit of the thickness of the substrate layer may be 100 μm or less, 90 μm or less, or 80 μm or less. That is, the thickness of the substrate layer may be 5 to 100 μm, 10 to 90 μm, or 15 to 80 μm. In one embodiment, the base layer is preferably a biaxially oriented polypropylene (OPP) film having a thickness of 5 to 80 μm.

[0024] <First layer> The laminate film according to the first embodiment includes a first layer laminated on at least one surface of a substrate layer and containing a polyvinylidene chloride polymer as a main component. That is, the first layer is composed of a resin composition containing a polyvinylidene chloride polymer as a main component. The first layer may be laminated on a corona discharge-treated or plasma-treated surface of the substrate layer. In this embodiment, the first layer contains a polyvinylidene chloride polymer as a main component. In this specification, "main component" means that the polyvinylidene chloride polymer accounts for more than 50% by mass of the total mass (100% by mass). In one embodiment, of the components constituting the first layer, the polyvinylidene chloride polymer preferably accounts for 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more. In one embodiment, the first layer is preferably a film containing a resin containing a polyvinylidene chloride polymer as a main component, more preferably a film containing a resin made of a polyvinylidene chloride polymer, and even more preferably a film made of a resin made of a polyvinylidene chloride polymer. By providing such a first layer, a packaging film can be obtained that has high gas barrier properties due to the low oxygen permeability and moisture permeability that are characteristics of polyvinylidene chloride polymers, and that can further suppress deterioration of gas barrier properties in high-humidity environments.

[0025] (Polyvinylidene chloride polymer) In the present disclosure, the term "polyvinylidene chloride polymer" refers to a resin containing a homopolymer of vinylidene chloride and / or a copolymer in which vinylidene chloride monomer as a main component is polymerized with one or more other monomers. In one embodiment, the polyvinylidene chloride polymer is preferably a resin in which vinylidene chloride monomers account for 80% by mass or more, more preferably 85% by mass or more, and even more preferably 85% by mass or more. In one embodiment, the polyvinylidene chloride polymer is preferably a resin in which vinylidene chloride monomers account for 60% by mass or more and 95% by mass or less, more preferably 70% by mass or more and 95% by mass or less, even more preferably 80% by mass or more and 95% by mass or less, and even more preferably 85% by mass or more and 95% by mass or less.

[0026] The other monomer is not particularly limited as long as it is a monomer that can be copolymerized with the vinylidene chloride monomer. Examples of the other monomer include acrylonitrile-based monomers, alkyl (meth)acrylate monomers, 2-methoxyethyl (meth)acrylate, 2-butoxyethyl (meth)acrylate, methoxytriethylene glycol (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, diethylene glycol (meth)acrylate, polyethylene glycol (meth)acrylate, 2-(dimethylamino)ethyl (meth)acrylate, N,N-dimethylacrylamide, N-methylol (meth)acrylamide, N-vinylpyrrolidone, vinyl propionate, vinyl stearate, vinyl chloride, vinyl acetate, and styrene.

[0027] Examples of the acrylonitrile monomer include (meth)acrylonitrile, fumaronitrile, maleonitrile, 2-chloroacrylonitrile, 3-ethoxyacrylonitrile, α-(2-cyanoethyl)acrylonitrile, etc. In one embodiment, the acrylonitrile monomer is preferably (meth)acrylonitrile.

[0028] Examples of alkyl (meth)acrylate monomers include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, n-amyl (meth)acrylate, isoamyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, decyl (meth)acrylate, and undecyl (meth)acrylate. In one embodiment, the alkyl (meth)acrylate monomer is preferably an alkyl (meth)acrylate monomer in which the alkyl group has 1 to 4 carbon atoms.

[0029] In one embodiment, the polyvinylidene chloride polymer is preferably a copolymer of vinylidene chloride monomer and one or more other monomers selected from the group consisting of (meth)acrylonitrile monomers, alkyl (meth)acrylate monomers, and 2-hydroxyethyl (meth)acrylate. In one embodiment, the polyvinylidene chloride polymer is preferably a copolymer of vinylidene chloride monomer and one or more other monomers selected from the group consisting of (meth)acrylonitrile monomers and alkyl (meth)acrylate monomers having an alkyl group having 1 to 4 carbon atoms.

[0030] In one embodiment, the polyvinylidene chloride polymer is a copolymer containing a vinylidene chloride monomer, an acrylonitrile monomer, and an alkyl (meth)acrylate monomer. In at least one embodiment, the polyvinylidene chloride polymer is preferably a copolymer containing a vinylidene chloride monomer, one or more acrylonitrile monomers, and one or more alkyl (meth)acrylate monomers. In one embodiment, the polyvinylidene chloride polymer is a copolymer containing vinylidene chloride monomer, (meth)acrylonitrile, and an alkyl (meth)acrylate monomer whose alkyl group has from 1 to 4 carbon atoms. In at least one embodiment, the polyvinylidene chloride polymer is preferably a copolymer containing vinylidene chloride monomer, one or two monomers selected from the group consisting of (meth)acrylonitrile, and one or two or more monomers selected from the group consisting of alkyl (meth)acrylate monomers whose alkyl group has from 1 to 4 carbon atoms.

[0031] In one embodiment, the polyvinylidene chloride polymer preferably contains 85% by mass or more and 95% by mass or less of vinylidene chloride, 1% by mass or more and 10% by mass or less of one or two types selected from the group consisting of (meth)acrylonitrile, and 0.5% by mass or more and 5% by mass or less of one or more types selected from the group consisting of alkyl (meth)acrylate monomers whose alkyl group has 1 to 4 carbon atoms.

[0032] The molecular weight of the polyvinylidene chloride polymer is not particularly limited. In one embodiment, the molecular weight of the polyvinylidene chloride polymer is 10,000 to 500,000, preferably 20,000 to 250,000, and more preferably 25,000 to 100,000, in terms of weight average molecular weight measured by gel permeation chromatography (GPC). When the weight average molecular weight is within the above range, a laminate film with excellent gas barrier properties can be obtained.

[0033] (Isocyanate) In one embodiment, the first layer preferably further contains an isocyanate. When the first layer further contains an isocyanate, the adhesion between the base layer and the first layer is improved, and the deterioration of the gas barrier property of the laminate film in a high-humidity environment can be further suppressed. The isocyanate is not particularly limited, and examples thereof include aliphatic polyisocyanates, aromatic polyisocyanates, araliphatic polyisocyanates, and alicyclic polyisocyanates.

[0034] Examples of aromatic polyisocyanates include 4,4'-, 2,4'-, or 2,2'-diphenylmethane diisocyanate or a mixture thereof (MDI), 2,4- or 2,6-tolylene diisocyanate or a mixture thereof (TDI), 4,4'-toluidine diisocyanate (TODI), 1,5-naphthalene diisocyanate (NDI), m- or p-phenylene diisocyanate or a mixture thereof, 4,4'-diphenyl diisocyanate, 4,4'-diphenyl ether diisocyanate, tolylene diisocyanate-trimethylolpropane adduct, etc. These may be used alone or in combination of two or more.

[0035] Examples of aromatic aliphatic polyisocyanates include 1,3- or 1,4-xylylene diisocyanate or a mixture thereof (XDI), 1,3- or 1,4-tetramethylxylylene diisocyanate or a mixture thereof (TMXDI), ω,ω'-diisocyanato-1,4-diethylbenzene, etc. These may be used alone or in combination of two or more.

[0036] Examples of alicyclic polyisocyanates include 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate, IPDI), 4,4'-, 2,4'-, or 2,2'-dicyclohexylmethane diisocyanate, or mixtures thereof (H 12 Examples of suitable isocyanates include 1,3- or 1,4-bis(isocyanatomethyl)cyclohexane or a mixture thereof (hydrogenated xylylene diisocyanate, H6XDI), bis(isocyanatomethyl)norbornane (NBDI), 1,3-cyclopentene diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, methyl-2,4-cyclohexane diisocyanate, and methyl-2,6-cyclohexane diisocyanate. These may be used alone or in combination of two or more.

[0037] Examples of aliphatic polyisocyanates include hexamethylene diisocyanate (HDI), trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, 1,2-, 2,3- or 1,3-butylene diisocyanate, 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, and the like.

[0038] The isocyanate may also include polymers of the above polyisocyanates (for example, dimers, trimers, pentamers, heptamers, etc.), biuret-modified products produced by the reaction of the above polyisocyanates with water, allophanate-modified products produced by the reaction of the above polyisocyanates with monools or polyhydric alcohols (described later), and oxadiazinetrione-modified products produced by the reaction of the above polyisocyanates with carbon dioxide gas.

[0039] Among these, from the viewpoint of gas barrier properties, aromatic polyisocyanates such as MDI, TDI, TODI, and NDI; aromatic aliphatic polyisocyanates such as XDI and TMXDI; IPDI, H 12 It is preferable to use alicyclic polyisocyanates such as MDI, H6XDI, NBDI, etc., or aliphatic polyisocyanates such as HDI, etc. Two or more of these may be used in combination.

[0040] In one embodiment, the thickness of the first layer is preferably 0.2 to 4.0 μm, more preferably 0.2 to 2.0 μm, even more preferably 0.4 to 2.0 μm, and particularly preferably 0.4 to 1.5 μm.

[0041] In one embodiment, the content of the isocyanate in the first layer is preferably 0.1 to 15 mass%, more preferably 0.5 to 10 mass%, even more preferably 0.8 to 8 mass%, and particularly preferably 1 to 5 mass%. The content of the isocyanate in the first layer can be adjusted by adding an isocyanate to the polyvinylidene chloride polymer contained as a main component in the first layer.

[0042] In one embodiment, an anchor coat layer may be formed between the substrate layer and the first layer. The anchor coat layer can be formed by applying an anchor coat agent to the substrate layer. As the anchor coat agent, a conventionally known anchor coat agent can be used, and anchor coat agents for food packaging films are particularly preferably used. From the viewpoint of easily achieving the effects of the present disclosure, it is preferable to have a configuration in which the first layer is laminated directly on the substrate layer.

[0043] <Second layer> The second layer is a layer containing at least one selected from a metal and an inorganic oxide as a main component. By configuring the second layer to be laminated directly on the first layer, deterioration of gas barrier properties and appearance in a high-humidity environment can be suppressed. In the present disclosure, "directly laminated" means that no other layer exists between the first layer and the second layer. If necessary, another layer may be laminated on the second layer.

[0044] The second layer contains at least one selected from a metal and an inorganic oxide as a main component. The term "main component" is as defined above. In one embodiment, of the components constituting the second layer, the metal or inorganic oxide preferably accounts for 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 80% by mass or more. In one embodiment, the second layer is preferably a vapor-deposited film containing at least one selected from a metal and an inorganic oxide as a main component, and more preferably a vapor-deposited film consisting of at least one selected from a metal and an inorganic oxide. The metal contained in the second layer is preferably aluminum. As the inorganic oxide contained in the second layer, a metal oxide is preferable. Preferable examples include aluminum oxide, silicon oxide, magnesium oxide, tin oxide, etc. Among these, the second layer is preferably a vapor deposition film containing at least one selected from aluminum oxide and silicon oxide as a main component, and particularly preferably a vapor deposition film containing aluminum oxide as a main component. In the present disclosure, aluminum oxide is AlO x (0 < x ≦ 1.5), and silicon oxide may be SiO x (0 < x ≦ 2.0). As long as the effects of the present disclosure are not inhibited, the second layer may contain other elements other than aluminum oxide and silicon oxide. In one embodiment, it is preferable that the second layer is a vapor deposition film containing at least one selected from aluminum, aluminum oxide, and silicon oxide as a main component, and more preferably a vapor deposition film containing aluminum as a main component. In one embodiment, the second layer is preferably a layer containing vapor-deposited aluminum, and more preferably a layer composed of vapor-deposited aluminum.

[0045] From the viewpoint of gas barrier properties, the thickness of the second layer is preferably 3 nm or more, more preferably 10 nm or more, and further preferably 30 nm or more. Also, the upper limit is preferably 300 nm or less, and more preferably 100 nm or less. When the second layer is a vapor deposition film, the thickness of the second layer can be adjusted according to the vapor deposition conditions described later.

[0046] <Protective layer> The laminated film according to the first embodiment may further include a protective layer. The protective layer is a layer laminated on the second layer. By providing the protective layer, the gas barrier properties of the laminated film are more likely to be further improved. The protective layer may contain, for example, polyvinyl alcohol-based resins, polysaccharides such as starch, methyl cellulose, and carboxymethyl cellulose, water-soluble polymers such as hydroxyl-containing polymeric acrylic resins, polyurethane-based resins, polyester-based resins, acrylic resins, titanium-based resins, isocyanate-based resins, imine-based resins, polybutadiene-based resins, etc. These may be used alone or in combination of two or more. Furthermore, these resins may be used in combination with a curing agent.

[0047] In one embodiment, from the viewpoint of easily improving the gas barrier property, the protective layer is formed by mixing a water-soluble polymer and a compound represented by the general formula: M(OR) n and / or a hydrolyzate thereof, and more preferably a water-soluble polymer and a siloxane-based compound in which M in the above general formula contains silicon. The water-soluble polymer preferably contains a polyvinyl alcohol-based resin.

[0048] The thickness of the protective layer is not particularly limited as long as the effects of the present disclosure are achieved, but it is preferably 0.1 to 1 μm.

[0049] <Application> As described above, the laminate film according to the first embodiment can further suppress the deterioration of gas barrier properties in a high-humidity environment. Such a laminate film can be suitably used as various packaging films that require gas barrier properties in a high-humidity environment, for example, as a packaging film for packaging food. In one embodiment, the laminate film according to the first embodiment is preferably a packaging film.

[0050] [Laminated film manufacturing method] A second embodiment of the present disclosure relates to a method for producing the laminated film according to the first embodiment. The manufacturing method according to the second embodiment includes laminating a first layer on at least one surface of a base layer (step (1)), and laminating a second layer directly on the first layer (step (2)). An example of the production method including steps (1) and (2) will be described below.

[0051] <Step (1): Laminating the first layer> Step (1) is a step of laminating a first layer on at least one surface of a substrate layer. In one embodiment, the lamination step is preferably performed by preparing a coating agent containing a polyvinylidene chloride polymer as a main component and applying the coating agent to the substrate layer. In one embodiment, a coating agent preparation step (step (1')) may be included before step (1).

[0052] (Step (1'): Preparation of coating agent) The coating agent can be prepared, for example, by adding a predetermined amount of polyvinylidene chloride polymer to a solvent capable of dissolving the polyvinylidene chloride polymer and mixing them together. The solid content concentration in the coating agent can be set within any range, but in one embodiment, the solid content concentration in the coating agent is preferably 5 to 20%.

[0053] The obtained coating agent is applied onto a substrate layer. As the substrate layer to which the coating agent is applied, it is preferable to use the above-mentioned film. In one embodiment, the substrate layer is preferably a polypropylene-based resin film, more preferably a biaxially oriented polypropylene (OPP) film.

[0054] The amount of coating agent applied (weight of the first layer after drying) can be appropriately selected depending on the size of the substrate layer, the desired thickness of the first layer, etc. In one embodiment, the amount of coating agent applied (weight of the first layer after drying) is 0.2 to 5.0 g / m 2 It is preferable that the density is 0.5 to 2.4 g / m 2 More preferably, it is 0.5 to 1.8 g / m 2 It is even more preferred that:

[0055] The method for applying the coating agent to the substrate layer is not particularly limited, and known methods and devices such as gravure coating, reverse coating, doctor coating, bar coating, and dip coating can be used.

[0056] By performing a heat treatment after coating, a first layer is formed on at least one surface of the substrate layer as the solvent evaporates, and the first layer is laminated on the substrate layer. The temperature of the heat treatment may be, for example, 80°C or higher, 90°C or higher, or 100°C or higher. The upper limit may be 140°C or lower, or 120°C or lower. The heat treatment time can be appropriately changed depending on the type of solvent, the amount applied, and the temperature.

[0057] In one embodiment, an aging treatment may be further performed after the heat treatment. The temperature of the aging treatment may be 40° C. or higher, or 50° C. or higher, and the upper limit may be 60° C. or lower. The time for the aging treatment may be, for example, one day or longer.

[0058] <Step (2): Laminating the second layer> Step (2) is to directly laminate a second layer containing at least one selected from a metal and an inorganic oxide as a main component on the first layer obtained in step (1). "Directly laminate" means that the second layer is laminated on the first layer without forming any other layer between the first and second layers or applying any adhesive or the like between the first and second layers. From the viewpoint of easily obtaining a laminated film with excellent gas barrier properties, the second layer is preferably a vapor-deposited film containing at least one selected from a metal and an inorganic oxide, and more preferably a vapor-deposited film consisting of at least one selected from a metal and an inorganic oxide. Examples of the metal and inorganic oxide that can be used include those described above. In one embodiment, the metal contained in the second layer is preferably aluminum. In one embodiment, the second layer is preferably a layer containing vapor-deposited aluminum, and more preferably a layer consisting of vapor-deposited aluminum.

[0059] The deposition method is not particularly limited, and known methods and devices can be used, and may be physical vapor deposition (PVD) or chemical vapor deposition (CVD). Examples of physical vapor deposition methods include vacuum deposition, reactive vapor deposition, sputtering, reactive sputtering, ion plating, and reactive ion plating. Examples of chemical vapor deposition methods include plasma CVD and laser CVD. The deposition conditions may be appropriately selected so as to obtain a second layer of a desired thickness.

[0060] <Step (3): Laminating the protective layer> The manufacturing method according to this embodiment may further include laminating a protective layer on the second layer (step (3)). The protective layer may be formed by applying a coating agent containing a protective layer resin composition containing the above-mentioned resin, or a protective layer resin composition containing a water-soluble polymer and a metal alkoxide and / or its hydrolysate, onto the second layer. The coating agent may contain a solvent or a dispersion medium. The same coating method as exemplified in step (1) can be used.

[0061] A non-limiting list of exemplary embodiments and combinations of exemplary embodiments of the present disclosure are set forth below. [1] A substrate layer; a first layer laminated on at least one surface of the base material layer; a second layer containing at least one selected from a metal and an inorganic oxide as a main component; the substrate layer contains a thermoplastic resin, the first layer contains a polyvinylidene chloride polymer as a main component, A laminated film in which the second layer is laminated directly onto the first layer. [2] The laminated film according to [1], wherein the second layer is a vapor-deposited film containing, as a main component, at least one selected from aluminum, aluminum oxide, and silicon oxide. [3] The laminated film according to [1] or [2], wherein the first layer further contains an isocyanate. [4] The laminated film according to any one of [1] to [3], wherein the thermoplastic resin comprises a polyolefin resin. [5] The laminated film according to any one of [1] to [4], wherein the base layer is a biaxially oriented polypropylene film. [6] The laminated film according to any one of [1] to [5], wherein the thickness of the first layer is 0.2 to 4.0 μm. [7] The laminated film according to any one of [1] to [6], further comprising a protective layer laminated on the second layer. [8] The laminated film according to any one of [1] to [7], which is a packaging film. [9] A method for producing a laminated film according to any one of [1] to [8], laminating the first layer on at least one surface of the base layer; and laminating said second layer directly onto said first layer.

[10] The manufacturing method according to [9], wherein the second layer is a vapor-deposited film containing, as a main component, at least one selected from aluminum, aluminum oxide, and silicon oxide. [Example]

[0062] The effects of the present disclosure will be clarified below by examples, but the present disclosure should not be interpreted as being limited based on the description of these examples.

[0063] [Laminated film manufacturing] [Example 1] To 100 parts by weight of vinylidene chloride copolymer (manufactured by Asahi Kasei Corporation, "R204"), 3 parts by weight of tolylene diisocyanate was added and dissolved in a mixed solvent of toluene / tetrahydrofuran = 1 / 2 (weight ratio) to prepare a coating solution with a resin concentration of 10% by weight. A corona-discharge-treated biaxially oriented polypropylene (OPP) film (thickness: 20 μm) was prepared as the substrate layer. The coating solution was applied to the corona-discharge-treated surface of this substrate layer using a bar coater to a thickness of 1 μm after drying, and then dried in an oven at 100°C for 1 minute to form a first layer. Aluminum was directly vapor-deposited on the surface of the first layer by physical vapor deposition (PVD) to form a second layer, which was a vapor-deposited aluminum layer with a thickness of 50 nm, thereby obtaining the laminated film of Example 1. The laminated film of Example 1 has the following configuration. Base layer: Biaxially oriented polypropylene (OPP) film layer (thickness: 20 μm) First layer: Polyvinylidene chloride (PVDC) layer (thickness: 1 μm) Second layer: Vapor-deposited aluminum layer (thickness: 50 nm)

[0064] [Comparative Example 1] Five parts by mass of an olefin-modified polyvinyl alcohol resin (manufactured by Kuraray Co., Ltd., "Exeval (registered trademark) HR-3010") was added to 100 parts of distilled water, and the mixture was stirred at 90°C for one hour to dissolve. 0.2 parts by mass of polyethyleneimine (manufactured by Nippon Shokubai Co., Ltd., "Epomin P-1000 (product name)", weight-average molecular weight: 70,000, solid content concentration: 30% by weight) was then added to prepare a coating solution with a solid content concentration of 5% by weight. A laminated film was produced in the same manner as in Example 1 using the coating liquid. The laminated film of Comparative Example 1 has the following configuration. Base layer: Biaxially oriented polypropylene (OPP) film layer (thickness: 20 μm) First layer: Olefin-modified polyvinyl alcohol layer (thickness: 0.5 μm) Second layer: Vapor-deposited aluminum layer (thickness: 50 nm)

[0065] Comparative Example 2 Five parts by mass of polyvinyl alcohol (PVA) resin (Kuraray Co., Ltd., "3-98") was added to 100 parts of distilled water and dissolved by stirring at 90°C for 1 hour. 0.2 parts by mass of polyethyleneimine (Nippon Shokubai Co., Ltd., "Epomin P-1000 (product name)", weight average molecular weight: 70,000, solid content concentration: 30% by weight) was then added to prepare a coating solution with a solid content concentration of 5% by weight. A laminated film was produced in the same manner as in Example 1 using the coating liquid. The laminated film of Comparative Example 2 has the following configuration. Base layer: Biaxially oriented polypropylene (OPP) film layer (thickness: 20 μm) First layer: Polyvinyl alcohol (PVA) layer (thickness: 0.5 μm) Second layer: Vapor-deposited aluminum layer (thickness: 50 nm)

[0066] Comparative Example 3 A corona discharge-treated biaxially stretched polyethylene terephthalate (PET) film (thickness: 12 μm) was prepared as the substrate layer. Aluminum was directly vapor-deposited onto the corona discharge-treated surface of this substrate layer by physical vapor deposition (PVD) to form a second layer of vapor-deposited aluminum with a thickness of 50 nm, thereby obtaining a laminated film of Comparative Example 3. The laminated film of Comparative Example 3 has the following configuration. Base layer: Polyethylene terephthalate (PET) film layer (thickness: 12 μm) First layer: None Second layer: Vapor-deposited aluminum layer (thickness: 50 nm)

[0067] Comparative Example 4 To 100 parts by weight of vinylidene chloride copolymer (manufactured by Asahi Kasei Corporation, "R204"), 3 parts by weight of tolylene diisocyanate was added and dissolved in a mixed solvent of toluene / tetrahydrofuran = 1 / 2 (weight ratio) to prepare a coating solution with a resin concentration of 10% by weight. A corona-discharge-treated biaxially oriented polypropylene (OPP) film (thickness: 20 μm) was prepared as a substrate layer. The coating solution was applied to the corona-discharge-treated surface of this substrate layer using a bar coater so as to have a thickness of 1 μm after drying, and then dried in an oven at 100°C for 1 minute to form a first layer. A two-component curing urethane laminating adhesive was applied to the surface of the first layer using a bar coater to a dry thickness of 2 μm, and then dried for 30 seconds in an oven at 80° C. The adhesive-coated surface was bonded to the aluminum-vapor-deposited surface of an aluminum-vapor-deposited non-oriented polypropylene (CPP) film ("2203" manufactured by Toray Advanced Film Co., Ltd.), to obtain the laminated film of Comparative Example 4. That is, the laminated film of Comparative Example 4 has another resin layer (adhesive layer) laminated between a layer containing a polyvinylidene chloride polymer and a layer containing at least one selected from metals and inorganic oxides as a main component, i.e., the second layer is not laminated directly on the first layer. The laminated film of Comparative Example 4 has the following configuration. Base layer: Biaxially oriented polypropylene (OPP) film layer (thickness: 20 μm) First layer: Polyvinylidene chloride (PVDC) layer (thickness: 1 μm) Adhesive layer: Two-component curing urethane laminate adhesive layer (thickness: 2 μm) Second layer: Vapor-deposited aluminum layer on aluminum-deposited non-oriented polypropylene (CPP) film (vapor-deposited thickness: 50 nm, film thickness: 25 μm) Third layer: Aluminum-coated CPP film (coating thickness: 50 nm, film thickness: 25 μm) Table 1 shows the configuration of each laminate film according to the examples and comparative examples.

[0068] [Appearance changes after storage in a high humidity environment] After storing each laminated film at 85°C and 85% RH for 24 hours, the change in appearance of the second layer was visually observed and evaluated according to the following criteria. The results are shown in Table 1. A: No change in appearance was observed. B: Changes in appearance such as color change or pinholes were observed.

[0069] [Table 1]

[0070] As shown in Table 1, the laminate film of Example 1 was evaluated as A for change in appearance after 24 hours of storage under conditions of 85°C and 85% humidity, i.e., no change in appearance was observed. On the other hand, the laminate films of Comparative Examples were evaluated as B for change in appearance, and changes in appearance such as color change and pinholes in the second layer, i.e., deterioration of the second layer, were observed. Furthermore, as shown in Comparative Example 4, even when the first layer was a polyvinylidene chloride polymer, the aluminum layer became transparent when the first layer was not directly laminated with an inorganic layer. From the above results, it can be seen that the laminate film of Example 1 according to the first embodiment can further suppress deterioration of the second layer containing at least one selected from metals and inorganic oxides as a main component under high humidity environments, thereby providing a laminate film that can further suppress deterioration of gas barrier properties under high humidity environments. Furthermore, the laminate film of Example 1 was obtained by the manufacturing method according to the second embodiment.

Claims

1. a substrate layer; a first layer laminated on at least one surface of the base material layer; a second layer containing at least one selected from a metal and an inorganic oxide as a main component; the substrate layer contains a thermoplastic resin, the first layer contains a polyvinylidene chloride polymer as a main component, A laminated film in which the second layer is laminated directly onto the first layer.

2. The laminated film according to claim 1 , wherein the second layer is a vapor-deposited film containing, as a main component, at least one selected from aluminum, aluminum oxide, and silicon oxide.

3. The laminated film according to claim 1 or 2, wherein the first layer further comprises an isocyanate.

4. The laminated film according to claim 1 or 2, wherein the thermoplastic resin comprises a polyolefin resin.

5. 3. The laminated film according to claim 1, wherein the substrate layer is a biaxially oriented polypropylene film.

6. 3. The laminated film according to claim 1, wherein the thickness of said first layer is 0.2 to 4.0 μm.

7. The laminated film according to claim 1 or 2, further comprising a protective layer laminated on the second layer.

8. The laminated film according to claim 1 or 2, which is a packaging film.

9. A method for producing the laminated film according to claim 1 or 2, laminating the first layer on at least one surface of the base layer; and laminating said second layer directly onto said first layer.

10. The method according to claim 9 , wherein the second layer is a vapor-deposited film containing, as a main component, at least one selected from aluminum, aluminum oxide, and silicon oxide.

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