Laminated film and method for producing the same

Abstract

To provide a laminated film that achieves 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 laminated on the first layer, wherein the base material layer contains a thermoplastic resin, the first layer contains, as a main component, a water-soluble vinyl-based polymer, the sodium salt concentration in the first layer is less than 0.2 wt.%, and the second layer contains, as a main component, at least one selected from the group consisting of a metal and an inorganic oxide.

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 laminated on the first layer, the substrate layer contains a thermoplastic resin, the first layer contains a water-soluble vinyl polymer as a main component, the sodium salt concentration in the first layer is less than 0.2% by weight; It has been found that the above problems can be solved if the second layer is a laminated film containing at least one selected from metals and inorganic oxides as a main component. [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 gist of this disclosure. The present disclosure is not limited to 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 laminated on the first layer, the substrate layer contains a thermoplastic resin, the first layer contains a water-soluble vinyl polymer as a main component, the sodium salt concentration in the first layer is less than 0.2% by weight; The second layer contains at least one selected from a metal and an inorganic oxide as a main component. The laminated film according to the first embodiment can provide a packaging film that can further suppress the deterioration of gas barrier properties in a high humidity environment. Water-soluble vinyl polymers are water-soluble synthetic resins that have traditionally been used primarily as raw materials for synthetic fibers. However, in recent years, their unique properties have led to their use in a variety of fields, including film materials, emulsifying dispersants, adhesives, and binder resins. Water-soluble vinyl polymers are produced by polymerizing vinyl acetate monomers and saponifying the resulting polyvinyl acetate. The resulting water-soluble vinyl polymers typically contain sodium salts (especially sodium acetate). The present inventors have conducted extensive research and found that by lowering the sodium salt concentration in a layer containing a water-soluble vinyl polymer as a main component, deterioration of a layer containing at least one selected from a metal and an inorganic oxide can be further suppressed, thereby obtaining a laminate film that can further suppress deterioration of gas barrier properties in high-humidity environments.

[0012] <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"). (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.

[0013] Examples of polyolefin resins include polyethylene resins and polypropylene resins.

[0014] 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.

[0015] 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.

[0016] Furthermore, the polypropylene resin may have an atactic structure, an isotactic structure, a syndiotactic structure, or a metallocene structure.

[0017] 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.

[0018] The polyolefin resin contained in the substrate layer may be a biomass-derived polyolefin resin or a mechanically recycled or chemically recycled polyolefin resin.

[0019] (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.

[0020] 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.

[0021] 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.

[0022] <First layer> The laminate film according to the first embodiment includes a first layer containing a water-soluble vinyl polymer as a main component and laminated on at least one surface of a substrate layer. That is, the first layer is composed of a resin composition containing a water-soluble vinyl 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 a first embodiment, the first layer contains a water-soluble vinyl polymer as a main component. In this specification, the term "main component" means that the content exceeds 50% by mass of the total mass (100% by mass). In one embodiment, of the components constituting the first layer, the water-soluble vinyl 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 composed of a resin containing a water-soluble vinyl polymer as a main component, and more preferably a film composed of a resin consisting of a water-soluble vinyl 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 the water-soluble vinyl polymer, and that can further suppress deterioration of the gas barrier properties in a high-humidity environment.

[0023] (Water-soluble vinyl polymer) In this embodiment, the water-soluble vinyl polymer is a water-soluble resin containing a polymer obtained by polymerizing a monomer having a vinyl group. Examples of water-soluble vinyl polymers include vinyl alcohol polymers. Examples of vinyl alcohol polymers include homopolymers such as polyvinyl alcohol, and olefin-vinyl alcohol copolymers such as olefin-modified polyvinyl alcohol (e.g., C copolymers such as ethylene-vinyl alcohol copolymers). 2-10 (Preferably C 2-5 , more preferably C 2-3 ) olefin-vinyl alcohol copolymer) etc. These water-soluble vinyl polymers can be used alone or in combination of two or more. In one embodiment, from the viewpoint of gas barrier properties, the water-soluble vinyl polymer preferably contains an olefin-modified vinyl alcohol resin, and more preferably contains a polyvinyl alcohol (PVA) resin and / or an olefin-vinyl alcohol copolymer. From the viewpoint of gas barrier properties in a high humidity environment, the water-soluble vinyl polymer preferably contains an olefin-vinyl alcohol copolymer, and C 2-10(Preferably C 2-5 , more preferably C 2-3 ) It is more preferable that the polymer contains an olefin-vinyl alcohol copolymer, and even more preferable that the polymer contains an ethylene-vinyl alcohol copolymer.

[0024] The saponification degree of the vinyl alcohol polymer can be selected from the range of 80 mol% or more, preferably 96 mol% or more, more preferably 99 mol% or more (particularly 99.5 mol% or more). The polymerization degree of the vinyl alcohol polymer is, for example, 200 or more (e.g., 200 to 5000), preferably 300 to 5000, more preferably about 400 to 3000.

[0025] (sodium salt concentration) In a first embodiment, the first layer contains a water-soluble vinyl polymer as a main component, and the sodium salt concentration in the first layer is less than 0.2 wt%. In the present disclosure, the "sodium salt concentration in the first layer" refers to the concentration of sodium salt (particularly sodium acetate) derived from the water-soluble vinyl polymer contained in the first layer, and does not include sodium salt not derived from the water-soluble vinyl polymer. By having the sodium salt concentration in the first layer less than 0.2 wt%, deterioration of the layer containing at least one selected from metals and inorganic oxides is further suppressed. The sodium salt concentration in the first layer can be made less than 0.2 wt% by using a water-soluble vinyl polymer with a low concentration of sodium salt (particularly sodium acetate) as the water-soluble vinyl polymer raw material. The adjustment of the sodium salt concentration in the water-soluble vinyl polymer is described below. The sodium salt concentration in the first layer can be determined by separating the first layer from the laminated film by physical or chemical methods, and dissolving the first layer in an aqueous solution, and then subjecting the solution to liquid chromatography or the like. In one embodiment, it is preferred that the sodium salt concentration in the first layer is less than 0.15 wt %, more preferably less than 0.1 wt %, and even more preferably less than 0.05 wt %. In one embodiment, it is preferred that the sodium acetate concentration in the first layer be less than 0.15 wt %, more preferably less than 0.1 wt %, and even more preferably less than 0.05 wt %.

[0026] In one embodiment, the first layer preferably further contains a polyalkyleneimine. By including a polyalkyleneimine in the first layer, the adhesion between the base layer and the first layer is improved, and the gas barrier properties are further improved. The polyalkyleneimine is obtained by polymerizing one or more alkyleneimines having 2 to 6 carbon atoms by a conventional method. Examples of alkyleneimines having 2 to 6 carbon atoms include ethyleneimine, propyleneimine, 1,2-butyleneimine, 2,3-butyleneimine, and 1,1-dimethylethyleneimine. In one embodiment, the polyalkyleneimine is preferably polyethyleneimine or polypropyleneimine, and more preferably polyethyleneimine. Polyethyleneimine is obtained by polymerizing ethyleneimine and has a branched chain structure containing primary, secondary, and / or tertiary amine nitrogen atoms.

[0027] The weight average molecular weight of the polyalkyleneimine is preferably 1,000 to 1,000,000, more preferably 10,000 to 300,000, even more preferably 30,000 to 100,000, and particularly preferably 50,000 to 80,000, as measured by gel permeation chromatography (GPC).

[0028] 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.

[0029] 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.

[0030] In one embodiment, the first layer may further contain a layered inorganic compound. Examples of layered inorganic compounds include swellable hydrous silicates, such as smectite group clay minerals (montmorillonite, beidellite, nontronite, saponite, hectorite, sauconite, stevensite, etc.), vermiculite group clay minerals (vermiculite, etc.), kaolin-type minerals (halloysite, kaolinite, endelite, dickite, etc.), phyllosilicates (talc, pyrophyllite, mica, margarite, muscovite, phlogopite, tetrasilylic mica, taeniolite, etc.), jamonite group minerals (antigorite, etc.), and chlorite group minerals (chlorite, cookite, nanite, etc.). These layered inorganic compounds may be natural or synthetic. These layered inorganic compounds may be used alone or in combination. Among these layered inorganic compounds, smectite group clay minerals, particularly montmorillonite, are preferred.

[0031] <Second layer> The second layer is a layer directly laminated on the first layer. 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.

[0032] The second layer contains at least one selected from a metal and an inorganic oxide as a main component. Regarding the "main component", it is the same as described above. In one embodiment, it is preferable that the metal or the inorganic oxide among the components constituting the second layer occupies 60% by mass or more, more preferably 70% by mass or more, still 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 deposition film containing at least one selected from a metal and an inorganic oxide as a main component, and more preferably a vapor deposition film composed of at least one selected from a metal and an inorganic oxide. As the metal contained in the second layer, aluminum is preferable. 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 may be 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.

[0033] 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 even more preferably 30 nm or more. The upper limit is preferably 300 nm or less, more preferably 100 nm or less. When the second layer is a vapor deposition film, the thickness of the second layer can be adjusted by the vapor deposition conditions described below. From the viewpoint of gas barrier properties, the thickness of the entire laminated film is preferably 5 to 104 μm, more preferably 5 to 100 μm, even more preferably 5 to 90 μm, and particularly preferably 10 to 80 μm.

[0034] <Protective layer> The laminate film according to the first embodiment may further include a protective layer. The protective layer is a layer laminated on the second layer. By including the protective layer, the gas barrier properties of the laminate film are 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.

[0035] In one embodiment, from the viewpoint of easily improving the adhesion between the second layer and the protective layer, the protective layer preferably contains a polyurethane-based resin. The polyurethane-based resin may be the same as or different from the polyurethane resin (A) described above.

[0036] 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) nand / 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.

[0037] 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. When the laminated film further comprises a protective layer, the thickness of the entire laminated film is preferably 5 to 104 μm, more preferably 5 to 100 μm, even more preferably 5 to 90 μm, and particularly preferably 10 to 80 μm, from the viewpoint of gas barrier properties.

[0038] <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.

[0039] [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 on the first layer (step (2)). An example of the production method including steps (1) and (2) will be described below.

[0040] <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 carried out by preparing a coating agent containing a water-soluble vinyl 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).

[0041] (Step (1'): Preparation of coating agent) The coating agent can be prepared, for example, by adding a predetermined amount of a water-soluble vinyl polymer to water and mixing them. 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%. To adjust the sodium salt concentration in the first layer to less than 0.2 wt%, a commercially available water-soluble vinyl polymer that has been treated to reduce sodium salts (particularly sodium acetate) may be used as the water-soluble vinyl polymer used in the coating solution. Alternatively, since sodium salts (particularly sodium acetate) are soluble in polar solvents such as methanol and water, the commercially available water-soluble vinyl polymer can be washed with methanol or water, and then the water-soluble vinyl polymer can be separated from the washings by filtration or other methods, whereby the sodium salts (particularly sodium acetate) move into the filtrate, thereby reducing the sodium salt (particularly sodium acetate) concentration in the water-soluble vinyl polymer.

[0042] 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.

[0043] 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:

[0044] 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.

[0045] 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.

[0046] 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.

[0047] <Step (2): Laminating the second layer> Step (2) is to laminate a second layer containing at least one selected from metals and inorganic oxides as a main component on the first layer obtained in step (1). 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.

[0048] 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.

[0049] <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.

[0050] 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 laminated on the first layer, the substrate layer contains a thermoplastic resin, the first layer contains a water-soluble vinyl polymer as a main component, the sodium salt concentration in the first layer is less than 0.2% by weight; A laminated film, wherein the second layer contains, as a main component, at least one selected from a metal and an inorganic oxide. [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 water-soluble vinyl polymer contains an olefin-modified vinyl alcohol resin. [4] The laminated film according to any one of [1] to [3], wherein the first layer contains a polyalkyleneimine. [5] The laminated film according to any one of [1] to [4], wherein the thermoplastic resin is a polyolefin resin. [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 the second layer onto the first layer.

[10] The method according to [9], wherein the sodium salt concentration in the first layer is less than 0.2% by weight. [Example]

[0051] 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.

[0052] [Laminated film manufacturing] [Example 1] Five parts by mass of an olefin-modified polyvinyl alcohol resin (ethylene-modified polyvinyl alcohol resin, "Exceval (registered trademark) AQ-4104," manufactured by Kuraray Co., Ltd., sodium acetate concentration: 0.01% by weight) 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 (product name: Epomin P-1000, manufactured by Nippon Shokubai Co., Ltd., weight-average molecular weight: 70,000, solids concentration: 30% by weight) was then added to prepare a coating solution with a solids concentration of 5% 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 dry thickness of 0.5 μm, 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 of vapor-deposited aluminum 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: Olefin-modified polyvinyl alcohol (low sodium acetate) layer (thickness: 0.5 μm), sodium acetate concentration: 0.01 wt% Second layer: Vapor-deposited aluminum layer (thickness: 50 nm)

[0053] [Comparative Example 1] Five parts by mass of an olefin-modified polyvinyl alcohol resin (manufactured by Kuraray Co., Ltd., "Exceval (registered trademark) HR-3010," sodium acetate concentration: 1% by weight) 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), sodium acetate concentration: 1% by weight Second layer: Vapor-deposited aluminum layer (thickness: 50 nm)

[0054] Comparative Example 2 Five parts by mass of polyvinyl alcohol (PVA) resin (manufactured by Kuraray Co., Ltd., "3-98 (product name)", sodium acetate concentration: 1 wt%) was added to 100 parts of distilled water and dissolved by stirring at 90°C for one hour. 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 wt%) was further added to prepare a coating solution with a solid content concentration: 5 wt%. 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), sodium acetate concentration: 1% Second layer: Vapor-deposited aluminum layer (thickness: 50 nm)

[0055] 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)

[0056] [Changes in appearance 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.

[0057] [Table 1]

[0058] As shown in Table 1, the laminate film of Example 1 was evaluated as A for appearance change 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 appearance change, and changes in appearance such as color change and pinholes in the second layer, i.e., deterioration of the second layer, were observed. From the above results, it can be seen that the laminate film of Example 1 according to the first embodiment can provide a laminate film that can further suppress deterioration of the gas barrier property by further suppressing deterioration of the second layer containing at least one selected from metals and inorganic oxides as a main component under a high humidity environment. Also, 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 laminated on the first layer, the substrate layer contains a thermoplastic resin, the first layer contains a water-soluble vinyl polymer as a main component, the sodium salt concentration in the first layer is less than 0.2 wt. %; A laminated film, wherein the second layer contains, as a main component, at least one selected from a metal and an inorganic oxide.

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 water-soluble vinyl polymer comprises an olefin-modified vinyl alcohol resin.

4. 3. The laminate film according to claim 1, wherein the first layer comprises a polyalkyleneimine.

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

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 the second layer onto the first layer.

10. 10. The method of claim 9, wherein the sodium salt concentration in the first layer is less than 0.2% by weight.

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