Laminated film

Abstract

[Problem] To provide a laminate film which, when made into a gas barrier laminate film provided with an inorganic thin film layer, has excellent oxygen barrier properties and adhesion between layers in a normal state and after heat-moisture treatment, has good adhesion even when processed such as printing / laminating, and is easy to manufacture and excellent in economical efficiency. [Solution] A laminated film which has a coating layer on at least one surface of a base film, and which is characterized in that the coating layer is formed from a coating layer resin composition that contains a resin having an oxazoline group as a constituent component, and in that the coating layer has an inorganic thin film layer on the coating layer, a protective layer containing a urethane resin is provided on the inorganic thin film layer, the surface hardness of the laminated film is 350-700 N / mm2, and the arithmetic average roughness of the protective layer at 2 [mu] m is 0.5-2.0 nm.

Description

[0001] This application is a divisional application of the application with the application number 201880014564.7, the application date 2018 / 02 / 08, and the title "Laminated film". TECHNICAL FIELD

[0002] The present application relates to a laminated film used in the field of packaging of food, pharmaceutical products, industrial products, and the like. In detail, it relates to a laminated film which, when a gas barrier laminated film provided with an inorganic film layer is produced, by controlling the physical properties of the film surface, as a result, good gas barrier properties and adhesion, printability, and moisture resistance can be exhibited. BACKGROUND

[0003] For packaging materials used in food, pharmaceutical products, and the like, in order to suppress oxidation of proteins, fats, and the like, maintain taste, freshness, and maintain the efficacy of pharmaceutical products, it is required to have properties of blocking oxygen, water vapor, and the like, i.e., gas barrier properties. In addition, gas barrier materials used in solar cells, organic EL, and the like electronic devices, electronic components, and the like require higher gas barrier properties than packaging materials for food and the like.

[0004] Conventionally, in food applications requiring blocking of various gases such as water vapor and oxygen, a gas barrier laminate in which a metal film formed of aluminum or the like, an inorganic film formed of inorganic oxides such as silicon oxide and aluminum oxide is formed on the surface of a base film formed of plastic has been generally used. Among them, the laminate in which a film of inorganic oxides such as silicon oxide, aluminum oxide, and mixtures thereof (inorganic film layer) is formed is transparent and the contents can be confirmed, and thus is widely used.

[0005] However, the above-described gas barrier laminate has the following problems: in the post-processing step of the packaging material such as printing / laminating / bag making, and further in the conveying / flowing process, the inorganic film layer is physically damaged by bending load, and thus the gas barrier properties deteriorate. In the processing step, once the inorganic film layer is damaged, there is a concern that the gas barrier properties will greatly deteriorate due to the subsequent moisture treatment such as boiling / retort processing. In addition, films in which the interlayer adhesion between the vapor deposition layer and the resin in contact therewith is lacking also have the problem that peeling occurs due to bending load, the barrier properties deteriorate, or the contents leak out.

[0006] On the other hand, as a method for improving the deterioration of a gas barrier layered body having an inorganic thin film, a method of providing a cover layer formed of various water-based polyurethane resins, polyester resins, or a mixture of polyurethane and polyester between a polyester base film and an inorganic thin film layer formed by, for example, a vapor deposition method has been proposed (for example, Patent Literature 1). Furthermore, in order to improve the water resistance of the cover layer under a humid heat, a cover layer formed of an oxazoline group-containing water-soluble polymer has been reported (for example, refer to Patent Literature 2). The provision of a cover layer between a base film and an inorganic thin film can also be performed continuously in the film formation of the base, and a large cost reduction can be expected compared to the formation of a protective layer on the inorganic thin film. However, in the above-described configuration, since the cover layer itself has no gas barrier property, the contribution to the gas barrier property is largely dependent on the inorganic thin film layer, and there is a problem of insufficient gas barrier property.

[0007] In view of the above problems, a protective layer having a gas barrier property has been further provided on the inorganic thin film. For example, a method of applying a water-soluble polymer and an inorganic layered compound and a metal alkoxide or a hydrolyzate thereof on an inorganic thin film, and forming a composite of the inorganic layered compound and the water-soluble polymer on the inorganic thin film by a sol-gel method has been proposed. According to this method, although excellent properties are exhibited even after a humid heat treatment, there are problems that the properties are different at the start and end of the application (for example, for the outer peripheral portion and the inner peripheral portion when a roll-shaped film is manufactured for industrial circulation), or the properties are different due to a slight temperature difference in drying and heat treatment in the film width direction, or a large quality difference occurs depending on the environment at the time of manufacture. Furthermore, a problem has been pointed out that since the film obtained by the application by the sol-gel method lacks flexibility, if a bend or an impact is applied to the film, a pinhole or a defect is easily generated, and the gas barrier property is reduced. In addition, the surface wettability of the film applied by the sol-gel method is low, and a smooth surface is easily obtained, and thus there is a problem that the adhesion of ink at the time of printing processing or an adhesive at the time of lamination processing is not sufficient. In order to eliminate this problem, a change to a structure in which the components of the ink or the adhesive are more easily adhered to the sol-gel layer, or a countermeasure such as an extension of the aging time after the application, an increase in the adhesive film thickness, and the like is required, and there is a limitation in terms of productivity and economy (cost) at the time of processing.

[0008] Against this backdrop, the following improvement is desired: a resin layer can be formed on an inorganic thin film layer by a coating method without sol-gel reactions, i.e., a coating method with a degree of cross-linking reaction during coating with a resin as the main component. Examples of such improved gas-barrier laminates include: a gas-barrier laminate in which a resin layer containing an inorganic layered compound with a specific particle size and aspect ratio is coated on an inorganic thin film; a gas-barrier laminate in which a barrier resin containing a silane coupling agent is coated on an inorganic thin film; and a laminate in which a polyurethane containing m-phenylenediamine is coated on an inorganic thin film (see, for example, Patent Document 3).

[0009] However, the current situation is that no gas barrier film can be obtained by using any of the above methods. It must have excellent production stability and economy during manufacturing, maintain good barrier / adhesion after severe damp heat treatment, and have sufficient transfer / adhesion for ink during printing and adhesive during lamination.

[0010] Existing technical documents

[0011] Patent documents

[0012] Patent Document 1: Japanese Patent Application Publication No. 2-50837

[0013] Patent Document 2: Japanese Patent No. 5560708

[0014] Patent Document 3: Japanese Patent No. 4524463

[0015] Patent Document 4: Japanese Patent Application Publication No. 11-179836 Summary of the Invention

[0016] Problem to be solved by the invention

[0017] In Patent Document 2, the primary goal is to maintain resistance to boiling and thus no research was conducted on improving the gas barrier properties before treatment. Furthermore, Patent Document 3 investigated the humidity dependence of oxygen permeability, showing good values, but did not study the gas barrier properties or adhesion after harsh hydrothermal treatments such as boiling / cooking.

[0018] The present invention was made in view of the problems of the prior art. The objective is to provide a laminated film that, when fabricated as a gas barrier laminated film having an inorganic thin film layer, exhibits excellent oxygen barrier properties and interlayer adhesion under normal conditions and after undergoing damp heat treatment, and also has good adhesion during processing such as printing / lamination, and is easy to manufacture and economical.

[0019] Solution to the problem

[0020] The inventors discovered that by fabricating a laminated film consisting of a specific covering layer with excellent softness / adhesion and a specific barrier protective layer sandwiching an inorganic thin film layer, it is possible to improve the gas barrier properties before treatment and maintain its barrier and adhesive properties even after severe damp heat treatment, thus completing the present invention.

[0021] That is, the present invention comprises the following components.

[0022] (1) A laminated film, characterized in that a cover layer is provided on at least one side of a substrate film, the cover layer being formed of a cover layer resin composition comprising a resin having an oxazoline group as a constituent component, an inorganic film layer is provided on the cover layer, and a protective layer containing a polyurethane resin is provided on the inorganic film layer, wherein the surface hardness of the protective layer of the laminated film is 350 to 700 N / mm. 2 Furthermore, the arithmetic mean roughness of the aforementioned protective layer in a 2μm square is 0.5–2.0 nm.

[0023] (2) The laminated film according to (1) is characterized in that the aforementioned protective layer contains aromatic or aromatic aliphatic components.

[0024] (3) The laminated film according to (1) or (2) is characterized in that the aforementioned protective layer contains isophthalic diisocyanate.

[0025] (4) The laminated film according to any one of (1) to (3), characterized in that the amount of oxazoline group in the resin composition for the aforementioned cover layer is 5.1 to 9.0 mmol / g.

[0026] (5) The laminated film according to any one of (1) to (4), characterized in that the aforementioned covering layer contains an acrylic resin with an acid value of less than 10 mg KOH / g.

[0027] (6) The laminated thin film according to any one of (1) to (5), characterized in that the aforementioned inorganic thin film layer is a layer of composite oxide of silicon oxide and aluminum oxide.

[0028] Effects of the invention

[0029] According to the present invention, a laminated film can be provided that, when fabricating a gas barrier laminated film having an inorganic thin film layer, maintains excellent gas barrier properties under normal conditions, not to mention after undergoing severe hydrothermal treatment such as boiling, and exhibits good lamination strength (adhesion) without interlayer delamination. Furthermore, the laminated film of the present invention allows for consistent quality under a wide range of manufacturing conditions without material selection during processing steps such as printing and lamination, thus offering excellent economic efficiency and production stability, and providing a gas barrier film with homogeneous properties. Detailed Implementation

[0030] The laminated film of the present invention has a cover layer, an inorganic film layer, and a protective layer provided on at least one side of a plastic substrate film. First, the plastic substrate film will be described, followed by a description of the cover layer, the inorganic film layer, and other layers laminated thereon.

[0031] [Substrate Film]

[0032] As the substrate film used in this invention (hereinafter sometimes referred to as "substrate film"), for example, a film made by melting and extruding plastic and stretching, cooling, and heat-setting it along the length and / or width directions as needed can be used. Examples of plastics include polyamides such as nylon 4 / 6, nylon 6, nylon 6 / 6, and nylon 12; polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene 2,6-naphthalenedicarboxylate; polyolefins such as polyethylene, polypropylene, and polybutene; and polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, fully aromatic polyamides, polyamide-imide, polyimide, polyether-imide, polysulfone, polystyrene, and polylactic acid. Among these, polyesters are preferred in terms of heat resistance, dimensional stability, and transparency, and polyethylene terephthalate and copolymers formed by copolymerizing polyethylene terephthalate with other components are particularly preferred.

[0033] As a substrate film, any thickness of substrate film can be used according to the desired purpose and application, such as mechanical strength and transparency. There is no particular limitation on its film thickness, but it is usually recommended to be 5 to 250 μm. When used as packaging material, 10 to 60 μm is ideal.

[0034] There is no particular limitation on the transparency of the substrate film, but when used as a packaging material that requires transparency, it is ideal to have a light transmittance of more than 50%.

[0035] The substrate film can be a single-layer film formed from a single type of plastic, or a laminated film composed of two or more types of plastic films. There are no particular restrictions on the type, number, or method of lamination when making a laminated film; any known method can be selected according to the purpose.

[0036] In addition, as long as the purpose of the present invention is not compromised, surface treatments such as corona discharge treatment, glow discharge treatment, flame treatment, and surface roughening treatment can be applied to the substrate film. In addition, known anchoring coating treatment, printing, decoration, etc. can also be applied.

[0037] [Overlay]

[0038] The capping layer of this invention comprises a resin having oxazoline groups. It is particularly preferable that unreacted oxazoline groups are present in the capping layer. Oxazoline groups have a high affinity for inorganic films such as metal oxides, and can react with oxygen-deficient portions of inorganic oxides and metal hydroxides generated during the formation of the inorganic film layer, thus exhibiting strong adhesion to the inorganic film layer. Furthermore, the unreacted oxazoline groups present in the capping layer can react with carboxylic acid terminals generated through the hydrolysis of the substrate film and the capping layer to form crosslinks, maintaining the water resistance of the capping layer.

[0039] Furthermore, by allowing the unreacted oxazoline moiety and the reacted crosslinked moiety to coexist in the capping layer, a membrane that is both water-resistant and flexible is created. Therefore, when subjected to bending or other loads, stress on the inorganic film layer can be mitigated, resulting in suppression of the reduction in gas barrier properties.

[0040] While capping layers formed solely from resins containing oxazoline groups can exhibit resistance to damp heat treatment, prolonged / high-temperature damp heat treatments can sometimes lead to insufficient cohesion within the capping layer itself, resulting in deformation and damage to the inorganic film layer. Therefore, in this invention, to ensure the capping layer can adequately withstand more severe damp heat treatments, it is preferable to also contain an acrylic resin. The inclusion of an acrylic resin increases the cohesion of the capping layer, resulting in improved water resistance.

[0041] Furthermore, by including a polyurethane resin, particularly a polyurethane resin containing carboxylic acid groups, in the resin composition for the cover layer, the resistance to damp heat treatment of the cover layer can be further improved. That is, by reacting the carboxylic acid groups in the polyurethane resin with oxazoline groups, the cover layer is locally cross-linked and becomes a layer possessing the flexibility of polyurethane resin, thereby mitigating the stress of the inorganic film to a higher level.

[0042] By setting the above-mentioned covering layer, although the laminated film of the present invention is a laminate with an inorganic film layer, the gas barrier properties and interlayer adhesion of the inorganic film layer can be maintained after humid heat treatment such as steaming by the above-mentioned method.

[0043] Next, the composition of the resin composition for forming the coating layer will be described in detail.

[0044] (Resin with oxazoline group (A))

[0045] The capping layer of the present invention comprises a resin having an oxazoline group. Examples of resins having an oxazoline group include polymers having an oxazoline group obtained by copolymerizing a polymerically unsaturated monomer having an oxazoline group with other polymerically unsaturated monomers as needed by conventionally known methods (e.g., solution polymerization, emulsion polymerization, etc.).

[0046] Examples of polymerizable unsaturated monomers containing an oxazoline group include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, and 2-isopropenyl-5-ethyl-2-oxazoline. These can be used alone or in combination of two or more.

[0047] Other polymerizable unsaturated monomers include, for example, alkyl or cycloalkyl esters of (meth)acrylic acid with 1 to 24 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, lauryl (meth)acrylate, and isobornyl (meth)acrylate; hydroxyalkyl esters of (meth)acrylic acid with 2 to 8 carbon atoms, such as 2-hydroxyethyl (meth)acrylate and hydroxypropyl (meth)acrylate; vinyl aromatic compounds such as styrene and vinyltoluene; adducts of (meth)acrylamide, dimethylaminopropyl (meth)acrylamide, dimethylaminoethyl (meth)acrylate, glycidyl (meth)acrylate, and amines; polyethylene glycol (meth)acrylate; N-vinylpyrrolidone, ethylene, butadiene, chloroprene, vinyl propionate, vinyl acetate, and (meth)acrylonitrile. These can be used alone or in combination of two or more.

[0048] From the viewpoint of improving compatibility with other resins, wettability, crosslinking efficiency, and transparency of the coating layer, the resin containing oxazoline groups used in this invention is preferably a water-dispersible resin. To make the resin containing oxazoline groups a water-dispersible resin, it is preferable to contain a hydrophilic monomer as one of the aforementioned polymerizable unsaturated monomers.

[0049] Examples of hydrophilic monomers include 2-hydroxyethyl methacrylate, methoxy polyethylene glycol (meth)acrylate, monoester compounds of (meth)acrylate and polyethylene glycol, etc., which are monomers with polyethylene glycol chains; 2-aminoethyl methacrylate and its salts; (meth)acrylamide; N-hydroxymethyl (meth)acrylamide; N-(2-hydroxyethyl) (meth)acrylamide; (meth)acrylonitrile; sodium styrene sulfonate, etc. Among these, monomers with polyethylene glycol chains, such as methoxy polyethylene glycol (meth)acrylate and monoester compounds of (meth)acrylate and polyethylene glycol, which have high water solubility are preferred (the molecular weight of the introduced polyethylene glycol chain is preferably 150 to 700, especially from the viewpoint of water resistance, it is 150 to 200, and from the viewpoint of compatibility with other resins and transparency of the coating layer, it is 300 to 700).

[0050] In copolymers formed from polymerizable unsaturated monomers having an oxazoline group and other polymerizable unsaturated monomers, the molar percentage of polymerizable unsaturated monomers having an oxazoline group is preferably 30 to 70 mol%, more preferably 40 to 65 mol%.

[0051] For resins containing oxazoline groups, the oxazoline group content is preferably 5.1 to 9.0 mmol / g. More preferably, it is in the range of 6.0 to 8.0 mmol / g. Conventionally, examples of using resins containing oxazoline groups with an oxazoline group content of around 5.0 mmol / g have been reported for use in capping layers (see, for example, Patent Document 4). However, in this invention, a resin with a higher oxazoline group content is used. This is because by using a resin with a higher oxazoline group content, it is possible to form a cross-linked structure in the capping layer while leaving the oxazoline group in the capping layer. As a result, it helps to maintain gas barrier properties during humid heat treatment and improve flexural strength. As such oxazoline-containing resins, the "EPOCROS (registered trademark)" series commercially available from Nippon Shokubai Co., Ltd. is an example.

[0052] The proportion of resin containing oxazoline groups in the resin composition for the coating layer is preferably 20-60% by mass, more preferably 25-55% by mass, and even more preferably 30-50% by mass, out of 100% by mass of the total resin content. If the proportion of resin containing oxazoline groups is less than 20% by mass, there is a tendency that the effect of oxazoline groups in improving water resistance and adhesion will not be fully utilized. On the other hand, if it exceeds 60% by mass, there is a concern that there will be too many unreacted oxazoline groups, resulting in insufficient cohesion of the coating layer and reduced water resistance.

[0053] (Acrylic resin (B))

[0054] To improve the water resistance and solvent resistance of the coating layer, the aforementioned resin composition for the coating layer may contain an acrylic resin. As the acrylic resin, an acrylic resin whose main component is alkyl acrylate and / or alkyl methacrylate (hereinafter, sometimes collectively referred to as "(meth)acrylate") is used. Specifically, examples of acrylic resins include water-soluble or water-dispersible resins that typically contain alkyl methacrylate at a content of 40 to 95 mol%, and, if necessary, typically contain copolymerizable vinyl monomers having functional groups at a content of 5 to 60 mol%. By setting the content of alkyl methacrylate in the acrylic resin to 40 mol% or more, the coatability, film strength, and anti-blocking properties become particularly good. On the other hand, by setting the content of alkyl (meth)acrylate to 95 mol% or less and introducing at least 5 mol% of a compound with specific functional groups into the acrylic resin as a copolymer component, it is possible to facilitate water solubility and / or water dispersibility and to stabilize its state over a long period of time. As a result, improvements can be achieved in the adhesion between the capping layer and the substrate film, the strength of the capping layer due to the reaction within the capping layer, water resistance, solvent resistance, etc. The preferred range for the content of alkyl (meth)acrylate is 50 to 90 mol%, more preferably 60 to 85%.

[0055] Alkyl groups in (meth)acrylates include, for example, methyl, n-propyl, isopropyl, n-butyl, isobutyl, 2-ethylhexyl, lauryl, stearyl, cyclohexyl, etc.

[0056] Functional groups in copolymerizable vinyl monomers may include, for example, carboxyl, anhydride, sulfonic acid or its salts, amide or hydroxyalkylated amide, amino (including substituted amino), hydroxyalkylated amino or its salts, hydroxyl, epoxy, etc., with carboxyl, anhydride, and epoxy groups being particularly preferred. There may be only one type of these functional groups or two or more types.

[0057] Compounds with carboxyl or anhydride groups that can be used as vinyl monomers include, in addition to acrylic acid, methacrylic acid, itaconic acid, and maleic acid, their alkali metal salts, alkaline earth metal salts, and ammonium salts, and maleic anhydride can also be listed.

[0058] Compounds containing sulfonic acid groups or their salts that can be used as vinyl monomers include, for example, vinyl sulfonic acid, styrene sulfonic acid, metal salts (sodium, etc.) and ammonium salts of these sulfonic acids.

[0059] Compounds having an amide group or a hydroxyalkylated amide group that can be used as vinyl monomers include, for example, acrylamide, methacrylamide, N-methylmethacrylamide, hydroxymethylated acrylamide, hydroxymethylated methacrylamide, ureoyl vinyl ether, β-ureoyl isobutyl vinyl ether, ureoyl ethyl acrylate, etc.

[0060] Compounds that can be used as vinyl monomers and have an amino group, a hydroxyalkylated amino group, or their salts include, for example, diethylaminoethyl vinyl ether, 2-aminoethyl vinyl ether, 3-aminopropyl vinyl ether, 2-aminobutyl vinyl ether, dimethylaminoethyl methacrylate, dimethylaminoethyl vinyl ether, and compounds formed by hydroxymethylating their amino groups, as well as compounds formed by quaternization using halogenated alkanes, dimethyl sulfuric acid, sulcolones, etc.

[0061] Compounds containing hydroxyl groups that can be used as vinyl monomers include, for example, β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate, β-hydroxypropyl acrylate, β-hydroxypropyl methacrylate, β-hydroxyethylene ether, 5-hydroxypentylethylene ether, 6-hydroxyhexylethylene ether, polyethylene glycol monoacrylate, polyethylene glycol monomethacrylate, polypropylene glycol monoacrylate, and polypropylene glycol monomethacrylate.

[0062] Compounds with epoxide groups that can be used as vinyl monomers include, for example, glycidyl acrylate, glycidyl methacrylate, etc.

[0063] In addition to the aforementioned functionalized compounds that are alkyl esters of (meth)acrylate and vinyl monomers, waterborne acrylic resins may also contain, for example, acrylonitrile, styrene, butyl vinyl ether, monoalkyl or dialkyl maleate, monoalkyl or dialkyl fumarate, monoalkyl or dialkyl itaconic acid, methyl vinyl ketone, vinyl chloride, vinylidene chloride, vinyl acetate, vinylpyridine, vinylpyrrolidone, vinyltrimethoxysilane, etc.

[0064] Preferably, the acrylic resin contains carboxyl groups, and its acid value is preferably 10 mg KOH / g or less. More preferably, it is 8 mg KOH / g or less, and even more preferably, it is 5 mg KOH / g or less. When the acid value is 10 mg KOH / g or less, the resin itself has excellent water resistance, so the cohesive strength of the coating layer can be improved even without crosslinking. If the acid value exceeds 10 mg KOH / g, although the strength of the coating layer is improved through crosslinking, there are concerns about reduced flexibility of the coating layer and increased stress on the inorganic film layer during cooking.

[0065] The proportion of acrylic resin in the resin composition constituting the cover layer is preferably 10-60% by mass, more preferably 15-55% by mass, and even more preferably 20-50% by mass, out of 100% by mass of the total resin content in the composition (e.g., the total of the aforementioned oxazoline-containing resin, acrylic resin, and the polyurethane resin described below). If the proportion of acrylic resin is less than 10% by mass, the effect of improving water resistance and solvent resistance may not be fully realized. On the other hand, if it exceeds 60% by mass, the cover layer becomes too hard, and therefore tends to increase the stress load on the inorganic film layer during damp heat treatment.

[0066] (Polyurethane Resin (C))

[0067] Preferably, the resin composition constituting the cover layer contains a polyurethane resin.

[0068] As polyurethane resins, water-soluble or water-dispersible resins obtained by reacting a polyhydroxy compound (polyol component) with a polyisocyanate compound using conventional methods can be used, for example. In particular, since waterborne polyurethane resins have improved affinity for aqueous media, polyurethane resins containing carboxyl groups or their salts are preferred. It should be noted that the composition of these polyurethane resins can be determined by nuclear magnetic resonance analysis, etc.

[0069] Examples of polyhydroxy compounds that are components of polyurethane resins include polyethylene glycol, polypropylene glycol, polyethylene glycol-propylene glycol, polytetramethylene glycol, hexamethylene glycol, tetramethylene glycol, 1,5-pentanediol, diethylene glycol, triethylene glycol, neopentanediol, polycaprolactone, polyhexamethylene adipate, polyhexamethylene sebacate, polytetramethylene adipate, polytetramethylene sebacate, trimethylolpropane, trimethylolethane, pentaerythritol, and glycerin.

[0070] Examples of polyisocyanate compounds that are components of polyurethane resins include aromatic diisocyanates such as toluene diisocyanate (2,4- or 2,6-toluene diisocyanate or mixtures thereof) (TDI) and diphenylmethane diisocyanate (4,4'-, 2,4'- or 2,2'-diphenylmethane diisocyanate or mixtures thereof) (MDI); aromatic aliphatic diisocyanates such as phenyl dimethyl diisocyanate (XDI); alicyclic diisocyanates such as isophorone diisocyanate (IPDI), 4,4-dicyclohexylmethane diisocyanate and 1,3-bis(isocyanate methyl)cyclohexane; aliphatic diisocyanates such as 1,6-hexamethylene diisocyanate (HDI) and 2,2,4-trimethylhexamethylene diisocyanate; or polyisocyanates formed by pre-addition of one or more of these compounds with trimethylolpropane, etc.

[0071] To introduce carboxyl groups or their salts into polyurethane resins, for example, a polyol compound containing a carboxyl group, such as dimethylolpropionic acid or dimethylolbutyric acid, can be introduced as a copolymer component, and then neutralized using a salt-forming agent. Specific examples of salt-forming agents include trialkylamines such as ammonia, trimethylamine, triethylamine, triisopropylamine, tri-n-propylamine, and tri-n-butylamine; N-alkylmorpholines such as N-methylmorpholine and N-ethylmorpholine; and N-dialkylalkanolamines such as N-dimethylethanolamine and N-diethylethanolamine. These can be used alone or in combination of two or more.

[0072] The polyurethane resin preferably has carboxyl groups and an acid value in the range of 10–40 mg KOH / g. Therefore, the reaction between the oxazoline groups and carboxyl groups allows the capping layer to maintain flexibility even with partial crosslinking, achieving both further improvement in cohesion and stress relief of the inorganic film. More preferably, the acid value is in the range of 15–35 mg KOH / g, and even more preferably, in the range of 20–30 mg KOH / g.

[0073] When the coating layer contains polyurethane resin, the proportion of polyurethane resin in the resin composition constituting the coating layer is preferably 10-60% by mass, more preferably 15-55% by mass, and even more preferably 20-50% by mass, out of 100% by mass of the total resin content in the composition (e.g., the total of the aforementioned oxazoline-containing resin, acrylic resin, and the polyurethane resin described below). By containing polyurethane resin within the above range, improved water resistance can be expected.

[0074] In the resin composition for the capping layer, the amount of carboxyl groups [mmol] relative to the amount of oxazoline groups [mmol] is preferably 20 mmol% or less, more preferably 15 mmol% or less. If the amount of carboxyl groups exceeds 20 mmol%, the crosslinking reaction will proceed excessively during the formation of the capping layer, thereby consuming a large number of oxazoline groups, reducing the adhesion to the inorganic film layer and the flexibility of the capping layer. As a result, there is a concern that the gas barrier properties and adhesion after humid heat treatment may be compromised.

[0075] In this invention, it is preferable to set the coating layer adhesion amount to 0.010–0.200 g / m³. 2 This allows for uniform control of the capping layer, resulting in a dense deposition of the inorganic thin film layers. Furthermore, the increased cohesion of the capping layer itself and the improved adhesion between the inorganic thin film layer, capping layer, and substrate film layers enhance the water resistance of the capping layer. The preferred capping layer adhesion amount is 0.015 g / m². 2 The above, and more preferably, is 0.020 g / m 2 The above, and more preferably, is 0.025 g / m 2 The preferred value is 0.190 g / m³.2 The following, or more preferably, is 0.180 g / m 2 The following, and more preferably, is 0.170 g / m 2 The following applies if the coating layer adhesion exceeds 0.200 g / m². 2 If the cohesion within the capping layer is insufficient, and the uniformity of the capping layer also decreases, defects may sometimes occur in the inorganic film layer, failing to fully demonstrate the gas barrier properties before and after the humid heat treatment. Furthermore, not only does the gas barrier property decrease, but the manufacturing cost also increases, which is economically disadvantageous. On the other hand, if the capping layer thickness is less than 0.010 g / m... 2 There is a concern that sufficient air barrier properties and interlayer tightness may not be achieved.

[0076] It should be noted that, as needed and without prejudice to the present invention, the resin composition for the coating layer may contain various known inorganic and organic additives such as antistatic agents, lubricants, and antiblocking agents.

[0077] There are no particular limitations on the method for forming the coating layer; for example, conventionally known methods such as coating can be used. Among coating methods, suitable methods include offline coating and online coating. For example, in the case of online coating performed in the process of manufacturing a substrate film, although the drying and heat treatment conditions during coating also depend on the coating thickness and the conditions of the apparatus, it is preferable to immediately send the film into a right-angle stretching process after coating and dry it in the preheating zone or stretching zone of the stretching process. In this case, a temperature of about 50 to 250°C is usually preferred.

[0078] [Inorganic Thin Film Layer]

[0079] The laminated film of the present invention has an inorganic film layer on the aforementioned cover layer.

[0080] Inorganic thin film layers are thin films formed from metals or inorganic oxides. There are no particular restrictions on the materials used to form inorganic thin film layers, as long as they can form a thin film. From the viewpoint of gas barrier properties, inorganic oxides such as silicon dioxide (Silica), aluminum oxide (Alumina), and mixtures of silicon dioxide and aluminum oxide are preferred. In particular, composite oxides of silicon dioxide and aluminum oxide are preferred from the perspective of balancing the flexibility and density of the thin film layer. In this composite oxide, the mixing ratio of silicon dioxide to aluminum oxide is preferably in the range of 20% to 70% by mass of the metal component (Al). If the Al concentration is less than 20%, the water vapor barrier properties may decrease. On the other hand, if it exceeds 70%, the inorganic thin film layer tends to harden, raising concerns that the film may be damaged during secondary processing such as printing and lamination, resulting in reduced barrier properties. It should be noted that silicon dioxide referred to here refers to various silicon oxides such as SiO and SiO2, or mixtures thereof, and aluminum oxide refers to various aluminum oxides such as AlO and Al2O3, or mixtures thereof.

[0081] The thickness of the inorganic thin film layer is typically 1–100 nm, preferably 5–50 nm. If the thickness of the inorganic thin film layer is less than 1 nm, it is sometimes difficult to obtain satisfactory gas barrier properties. On the other hand, even if it exceeds 100 nm and becomes too thick, the effect of improving gas barrier properties is not comparable, and it becomes disadvantageous in terms of bending resistance and manufacturing cost.

[0082] There are no particular limitations on the method for forming inorganic thin film layers. For example, known vapor deposition methods such as vacuum evaporation, sputtering, ion plating (PVD), or chemical vapor deposition (CVD) are suitable. The following describes a typical method for forming inorganic thin film layers using silicon oxide / alumina-based thin films as an example. For instance, in the case of vacuum evaporation, a mixture of SiO2 and Al2O3, or a mixture of SiO2 and Al, is preferably used as the vapor deposition raw material. Particles are typically used as the vapor deposition raw material; ideally, the size of each particle should be such that the pressure during vapor deposition does not change, with a preferred particle size of 1 mm to 5 mm. Heating can be performed using resistance heating, high-frequency induction heating, electron beam heating, laser heating, etc. Alternatively, reactive vapor deposition can be performed by introducing oxygen, nitrogen, hydrogen, argon, carbon dioxide, water vapor, etc., as the reaction gas, or by using ozone addition, ion-assisted methods, etc. Furthermore, the film formation conditions can be arbitrarily changed, such as applying a bias voltage to the deposited object (the stacked thin film for evaporation), or heating or cooling the deposited object. Similarly, the evaporation material, reactive gas, bias voltage of the deposited object, and heating / cooling can also be changed when using sputtering or CVD methods.

[0083] [Protective Layer]

[0084] In this invention, a protective layer is provided on the aforementioned inorganic thin film layer. The inorganic thin film layer laminated on the plastic film is not a completely dense film, but rather has scattered tiny defects. A protective layer is formed by coating the inorganic thin film layer with the specific protective layer resin composition described later, thereby allowing the resin in the protective layer resin composition to penetrate into the defects of the inorganic thin film layer, resulting in stable gas barrier properties. Furthermore, the protective layer itself uses a gas-barrier material, thereby significantly improving the gas barrier performance of the laminated film.

[0085] In this invention, the surface hardness of the protective layer of the laminated film is preferably 350–700 N / mm. 2 Therefore, the surface hardness required to achieve a tight seal is ideal, and it should maintain its properties even after cooking. A surface hardness of 375 N / mm² is preferred. 2 Above, or more preferably 400 N / mm 2 The above, further optimized, is 420N / mm. 2 The preferred value is 675 N / mm. 2 Below, more preferably 650 N / mm 2 The following is a further preferred value: 625 N / mm 2 The surface hardness of the protective layer of the laminated thin film exceeds 700 N / mm. 2 When the surface hardens excessively, the adhesive used in printing and lamination cannot penetrate, resulting in reduced adhesion. On the other hand, a surface hardness below 350 N / mm²... 2 At that time, the cohesive force of the protective layer is weak, and there is concern that the protection of the inorganic film layer becomes insufficient, and there is also concern that the pigment in the ink will be buried and the ink transferability (printing appearance) will deteriorate.

[0086] In this invention, the arithmetic mean roughness of the protective layer within a 2μm square viewing angle is preferably 0.50 to 2.0 nm. This maintains the uniformity of the protective layer and improves adhesion through the anchoring effect generated by the formation of minute surface irregularities. The arithmetic mean roughness is preferably 0.60 nm or more, more preferably 0.70 nm or more, further preferably 0.80 nm or more, preferably 1.9 nm or less, more preferably 1.8 nm or less, and further preferably 1.7 nm or less. When the arithmetic mean roughness exceeds 2.0 nm, the surface becomes excessively rough, reducing the uniformity of the protective layer. This results in unevenness and defects in the coating appearance, sometimes reducing printability. On the other hand, when the arithmetic mean roughness is below 0.5 nm, the surface becomes excessively flat, making it impossible to achieve the so-called anchoring effect, raising concerns about reduced adhesion and ink transfer during printing.

[0087] In this invention, to ensure that the surface hardness and arithmetic mean roughness of the protective layer are within the aforementioned specified range, it is preferable that the adhesion amount of the protective layer is 0.15–0.60 g / m. 2Therefore, uniformity reduces coating unevenness and defects, and the anchoring effect improves adhesion. Furthermore, the increased cohesiveness of the protective layer strengthens the bond between the inorganic film layer and the protective layer, also improving water resistance. The preferred coating weight is 0.17 g / m³. 2 Above, more preferably 0.20 g / m 2 The above, further optimized, is 0.23 g / m 2 The preferred value is 0.57 g / m³. 2 Below, more preferably 0.54 g / m 2 The following is a further preferred option: 0.51 g / m 2 The following applies: The amount of protective layer adhered exceeds 0.600 g / m². 2 At this time, while the gas barrier properties improve, the surface hardness decreases, and the cohesive force within the protective layer becomes insufficient, raising concerns about reduced adhesion. Furthermore, the arithmetic mean roughness of the protective layer also increases, resulting in uneven coating appearance, defects, or sometimes failing to fully demonstrate the gas barrier / adhesion properties after hydrothermal treatment. On the other hand, the film thickness of the protective layer is less than 0.15 g / m². 2 There are concerns that sufficient air barrier properties and interlayer tightness may not be achieved.

[0088] In this invention, a polyurethane resin is used as the protective layer. The polyurethane resin contains polar urethane bond portions, resulting in good adhesion to the metal oxide layer and easy resin penetration into damaged areas. Furthermore, it contains crystalline portions with high aggregation forces generated by hydrogen bonding between the urethane bonds, thus achieving stable gas barrier properties. Additionally, it also contains highly flexible amorphous portions; therefore, by controlling the ratio of amorphous to crystalline portions, the surface hardness can be kept within the aforementioned specified range. As the polyurethane resin, a highly polar aqueous dispersion system with good wettability to the metal oxide layer is preferred. Furthermore, from the viewpoint of production stability, a thermosetting resin is ideal as the resin curing type.

[0089] (Polyurethane resin (D))

[0090] Polyurethane resin (D) can be obtained by reacting the following polyisocyanate component (E) with the following polyol component (F) using conventional methods. Furthermore, chain extension can also be achieved by reacting low-molecular-weight compounds with two or more active hydrogen atoms, such as diols (e.g., 1,6-hexanediol) or diamines (e.g., hexamethylenediamine), as chain extenders.

[0091] (E) Polyisocyanate components

[0092] Polyisocyanate components (E) that can be used in the synthesis of polyurethane resin (D) include aromatic polyisocyanates, alicyclic polyisocyanates, and aliphatic polyisocyanates. Diisocyanate compounds are commonly used as polyisocyanate compounds.

[0093] Examples of aromatic diisocyanates include, for example, toluene diisocyanate (2,4- or 2,6-toluene diisocyanate or mixtures thereof) (TDI), phenyl diisocyanate (m-phenylene diisocyanate, terephthalene diisocyanate or mixtures thereof), 4,4'-biphenyl diisocyanate, 1,5-naphthalene diisocyanate (NDI), diphenylmethane diisocyanate (4,4'-, 2,4'-, or 2,2'-diphenylmethane diisocyanate or mixtures thereof) (MDI), 4,4'-dimethylbiphenyl diisocyanate (TODI), 4,4'-diphenyl ether diisocyanate, etc. Examples of aromatic aliphatic diisocyanates include, for example, phenyl dimethyl diisocyanate (1,3- or 1,4-phenyl dimethyl diisocyanate or mixtures thereof) (XDI), tetramethyl phenyl dimethyl diisocyanate (1,3- or 1,4-tetramethyl phenyl dimethyl diisocyanate or mixtures thereof) (TMXDI), ω,ω'-diisocyanate-1,4-diethylbenzene, etc.

[0094] Examples of alicyclic diisocyanates include 1,3-cyclopentene diisocyanate, cyclohexane diisocyanate (1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate), 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate, IPDI), methylene bis(cyclohexyl isocyanate) (4,4'-, 2,4'- or 2,2'-methylene bis(cyclohexyl isocyanate)) (hydrogenated MDI), methylcyclohexane diisocyanate (methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate), bis(isocyanate methyl)cyclohexane (1,3- or 1,4-bis(isocyanate methyl)cyclohexane or mixtures thereof) (hydrogenated XDI), etc.

[0095] Examples of aliphatic diisocyanates include trimethylene diisocyanate, 1,2-propylidene diisocyanate, butylidene diisocyanate (tetramethylene diisocyanate, 1,2-butylidene diisocyanate, 2,3-butylidene diisocyanate, 1,3-butylidene diisocyanate), hexamethylene diisocyanate, pentamethylene diisocyanate, 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, and 2,6-diisocyanate methyl caffeate.

[0096] (G) Polyol components

[0097] As a polyol component (especially a diol component), a range of diols from low molecular weight to high molecular weight can be used. From the viewpoint of gas barrier properties and the softness provided by amorphous parts, alkylene glycols (e.g., ethylene glycol, propylene glycol, trimethylene glycol, 1,3-butanediol, 1,4-butanediol, pentanediol, hexanediol, neopentanediol, heptahydrate, octanediol, etc., in straight-chain or branched form) can be used. 2-10 alkylene glycols), (poly)oxyC 2-4 Alkylene glycols (diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, etc.) and other low molecular weight glycols. The preferred glycol composition is C. 2-8 Polyol components [e.g., C] 2-6 Alkylene glycols (especially ethylene glycol, 1,2- or 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, etc.), dioxane or trioxane 2-3 Alkyl glycols (diethylene glycol, triethylene glycol, dipropylene glycol, etc.), with C being a particularly preferred glycol component. 2-8 Alkyl glycols (especially C16) 2-6 (alkylene glycols).

[0098] These diol components can be used alone or in combination of two or more. Furthermore, depending on the requirements, low molecular weight diol components such as aromatic diols (e.g., bisphenol A, dihydroxyethyl terephthalate, catechol, resorcinol, hydroquinone, 1,3- or 1,4-phenylenedimethyl diol or mixtures thereof), alicyclic diols (e.g., hydrogenated bisphenol A, phenylenedimethyl diol, cyclohexanediol, cyclohexanediol, etc.) can also be used in combination. Furthermore, depending on the requirements, polyol components with three or more functionalities can also be used in combination, such as glycerol, trimethylolethane, trimethylolpropane, polyester polyols, polycarbonate polyols, and polyether polyols. Preferably, the polyol components contain at least C... 2-8 Polyol components (especially C) 2-6 Alkylene glycols). C in 100% by mass of the polyol component. 2-8 Polyol components (especially C) 2-6 The proportion of alkylene glycols can be selected from about 50 to 100% by mass, and is generally preferred to be 70% or more and 100% or less by mass, more preferably 80% or more and 100% or less by mass, and even more preferably 90% or more and 100% or less by mass.

[0099] In this invention, from the perspective of improving the gas barrier properties arising from the formation of crystallization points derived from urethane bonds, it is more preferable to use a polyurethane resin containing an aromatic or aromatic aliphatic diisocyanate as a main component. Of particular preference is the presence of an isophthalic diisocyanate. By using the above-mentioned resin, the cohesive force of the urethane bonds can be further improved due to the stacking effect of the aromatic rings, resulting in good gas barrier properties. It is preferable to set the proportion of aromatic or aromatic aliphatic diisocyanates in the polyurethane resin to be 30 mol% or more (30 to 100 mol%) in 100 mol% of the polyisocyanate component (E). The total proportion of aromatic or aromatic aliphatic diisocyanates is preferably 40 to 100 mol%, more preferably 50 to 100 mol%, and even more preferably 60 to 100 mol%. As such a resin, the "TAKELAC (registered trademark)" series sold by Mitsui Chemicals Co., Ltd. can be appropriately used. If the total proportion of aromatic or aromatic aliphatic diisocyanates is less than 30 mol%, good gas barrier properties may not be obtained.

[0100] From the viewpoint of improving affinity with inorganic thin film layers, the aforementioned polyurethane resin preferably has carboxyl groups. To introduce carboxyl (salt) groups into the polyurethane resin, for example, polyol compounds with carboxyl groups, such as dimethylolpropionic acid or dimethylolbutyric acid, which are polyol components, can be introduced as copolymerizing components. Furthermore, after synthesizing the polyurethane resin containing carboxyl groups, neutralization with a salt-forming agent yields an aqueous dispersion of the polyurethane resin. Specific examples of salt-forming agents include trialkylamines such as ammonia, trimethylamine, triethylamine, triisopropylamine, tri-n-propylamine, and tri-n-butylamine; N-alkylmorpholines such as N-methylmorpholine and N-ethylmorpholine; and N-dialkylalkanolamines such as N-dimethylethanolamine and N-diethylethanolamine. These can be used alone or in combination of two or more.

[0101] (Properties of polyurethane resin)

[0102] The acid value of the polyurethane resin is preferably in the range of 10 to 60 mg KOH / g. More preferably, it is in the range of 15 to 55 mg KOH / g, and even more preferably, it is in the range of 20 to 50 mg KOH / g. If the acid value of the polyurethane resin is within the aforementioned range, the liquid stability is improved when preparing an aqueous dispersion. In addition, the protective layer can be uniformly deposited on the highly polar metal oxide layer, thus improving the coating appearance.

[0103] The glass transition temperature (Tg) of the polyurethane resin of the present invention is preferably 100°C or higher, more preferably 110°C or higher, and even more preferably 120°C or higher. By setting Tg to 100°C or higher, the surface hardness of the film can be easily adjusted within the aforementioned specified range.

[0104] In the polyurethane resin of the present invention, various additives may be incorporated as needed within a range that does not impair gas barrier properties. Examples of additives include silane coupling agents, layered inorganic compounds, stabilizers (antioxidants, heat stabilizers, ultraviolet absorbers, etc.), plasticizers, antistatic agents, lubricants, anti-blocking agents, colorants, fillers, and crystallizing nucleating agents.

[0105] In particular, silane coupling agents are effective in improving the adhesion of gas-barrier polyurethane resins to metal oxide layers. Examples of silane coupling agents include hydrolyzable alkoxysilane compounds, such as halogenated alkoxysilanes (e.g., 2-chloroethyltrimethoxysilane, 2-chloroethyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, etc., chloroC2-4 alkyltriC1-4 alkoxysilanes), and epoxy-containing alkoxysilanes [e.g., 2-glycidyl etheroxyethyltrimethoxysilane, 2-glycidyl etheroxyethyltriethoxysilane, 3-glycidyl etheroxyethyltriethoxysilane, etc.]. Glycidyl etheroxypropyltriethoxysilane and other glycidyl etheroxy C2-4 alkyltriC1-4 alkoxysilanes, 3-glycidyl etheroxypropylmethyldimethoxysilane, 3-glycidyl etheroxypropylmethyldiethoxysilane and other glycidyl etheroxydiC2-4 alkyldiC1-4 alkoxysilanes, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 3-(3,4-Epoxycyclohexyl)propyltrimethoxysilane, etc. (epoxycycloalkyl)C2-4 alkyltriC1-4 alkoxysilanes, etc., alkoxysilanes with amino groups [2-aminoethyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, etc., aminoC2-4 alkyltriC1-4 alkoxysilanes, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, etc., aminodiC2-4 alkyldiC1-4 alkoxysilanes, 2-[N-(2-aminoethyl)amino]ethyl 3-[N-(2-aminoethyl)amino]propyltrimethoxysilane, 3-[N-(2-aminoethyl)amino]propyltriethoxysilane, etc. (2-aminoC2-4 alkyl)aminoC2-4 alkyltriC1-4 alkoxysilanes, 3-[N-(2-aminoethyl)amino]propylmethyldimethoxysilane, 3-[N-(2-aminoethyl)amino]propylmethyldiethoxysilane, etc. (aminoC2-4 alkyl)aminodiC2-4 alkyldiC1-4 alkoxysilanes, etc., containing thiol groups. Alkoxysilanes (such as 2-mercaptoethyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, etc., mercapto-C2-4 alkyltriC1-4 alkoxysilanes, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropylmethyldiethoxysilane, etc., mercapto-diC2-4 alkyldiC1-4 alkoxysilanes, etc.), alkoxysilanes with vinyl groups (such as vinyltrimethoxysilane, vinyltriethoxysilane, etc., vinyltriC1-4 alkoxysilanes, etc.), alkoxysilanes with olefinic unsaturated groups […]. Silane coupling agents include 2-(meth)acryloyloxyethyltrimethoxysilane, 2-(meth)acryloyloxyethyltriethoxysilane, 3-(meth)acryloyloxypropyltrimethoxysilane, 3-(meth)acryloyloxypropyltriethoxysilane, etc. (meth)acryloyloxyC2-4alkyltriC1-4alkoxysilanes, 3-(meth)acryloyloxypropylmethyldimethoxysilane, 3-(meth)acryloyloxypropylmethyldiethoxysilane, etc. (meth)acryloyloxydiC2-4alkyldiC1-4alkoxysilanes, etc. These silane coupling agents can be used alone or in combination of two or more.

[0106] The proportion of the silane coupling agent relative to 100 parts by weight of polyurethane resin is less than 30 parts by weight (e.g., 0.1 to 30 parts by weight), preferably 0.5 to 20 parts by weight, and more preferably about 1 to 10 parts by weight.

[0107] When a protective layer is formed using a resin composition, a coating liquid (coating solution) formed from the aforementioned polyurethane resin, ion-exchanged water, and a water-soluble organic solvent can be prepared, coated onto a substrate film, and dried. As the water-soluble organic solvent, single or mixed solvents selected from alcohols such as ethanol and isopropanol (IPA), ketones such as acetone and methyl ethyl ketone, etc., can be used. From the viewpoint of coating processing and odor control, IPA is preferred.

[0108] The coating method for the protective layer resin composition is not particularly limited as long as it is applied to the film surface and forms a layer. For example, common coating methods such as gravure coating, reverse roller coating, wire rod coating, and die coating can be used. From the viewpoint of productivity and coating stability, wire rod coating and gravure coating are suitable.

[0109] When forming the protective layer, it is preferable to heat-dry it after coating with the resin composition for the protective layer. The drying temperature is preferably 110–210°C, more preferably 115–205°C, and even more preferably 120–200°C. If the drying temperature is below 110°C, insufficient drying or insufficient aggregation due to heat may occur in the protective layer, raising concerns that the surface hardness may not be within the specified range. As a result, there are concerns that the adhesion and water resistance of the protective layer after the boiling treatment may be reduced. On the other hand, if the drying temperature exceeds 210°C, excessive aggregation of the protective layer may occur, the film may become excessively hardened, or the resin may become homogenized through melting, raising concerns that a textured surface may not be obtainable. In addition, excessive heat applied to the film itself, which serves as the substrate, may cause the film to become brittle or shrink, raising concerns that processability may deteriorate. It should be noted that applying additional heat treatment (e.g., 150–190°C) other than drying is also effective in ensuring the drying of the protective layer.

[0110] As described above, the laminated film of the present invention is a gas barrier laminated film (laminated body) that is generally excellent in terms of oxygen barrier properties and interlayer adhesion after undergoing wet heat treatment, and also has good adhesion when subjected to processing such as printing / lamination. Furthermore, it is easy to manufacture and economically efficient.

[0111] [Other layers]

[0112] In the gas barrier laminated film having an inorganic film layer formed by using the laminated film of the present invention, in addition to the above-mentioned substrate film, cover layer, inorganic film layer and protective layer, various layers known to be present in the gas barrier laminated film may be provided as needed.

[0113] For example, when using a gas-barrier laminated film with an inorganic film layer as a packaging material, it is preferable to form a heat-sealable resin layer called a sealant. The heat-sealable resin layer is usually disposed on the inorganic film layer, but sometimes it is disposed on the outside of the substrate film (the side opposite to the surface where the cover layer is formed). The heat-sealable resin layer is usually formed by extrusion lamination or dry lamination. As for the thermoplastic polymer forming the heat-sealable resin layer, it can be polyethylene resins such as HDPE, LDPE, and LLDPE, polypropylene resins, ethylene-vinyl acetate copolymers, ethylene-α-olefin random copolymers, ionomer resins, etc., as long as they can sufficiently exhibit sealing and adhesive properties.

[0114] Furthermore, in the gas barrier laminated film having an inorganic thin film layer, at least one or more printed layers, other plastic substrates and / or paper substrates may be laminated between or on the outside of the inorganic thin film layer or the substrate film and the heat-sealing resin layer.

[0115] As the printing ink for forming the printing layer, water-based and solvent-based resin-containing printing inks are preferred. Examples of resins used in this printing ink include acrylic resins, polyurethane resins, polyester resins, vinyl chloride resins, vinyl acetate copolymer resins, and mixtures thereof. The printing ink may contain known additives such as antistatic agents, opacifiers, UV absorbers, plasticizers, lubricants, fillers, colorants, stabilizers, defoamers, crosslinking agents, antiblocking agents, and antioxidants. The printing method for setting the printing layer is not particularly limited, and known printing methods such as offset printing, gravure printing, and screen printing can be used. Known drying methods such as hot air drying, hot roller drying, and infrared drying can be used for drying the solvent after printing.

[0116] On the other hand, from the viewpoint of obtaining sufficient rigidity and strength of the laminate, paper, polyester resin, polyamide resin, and biodegradable resin are preferred as other plastic or paper substrates. Furthermore, in terms of producing films with excellent mechanical strength, biaxially stretched polyester films, biaxially stretched nylon films, and other stretched films are preferred.

[0117] Especially when using gas-barrier laminated films with inorganic film layers as packaging materials, it is preferable to laminate a nylon film between the inorganic film layer and the heat-sealing resin layer to improve mechanical properties such as pinhole resistance and puncture strength. Common types of nylon used here include nylon 6, nylon 66, and m-xylene adipamide. The thickness of the nylon film is typically 10–30 μm, preferably 15–25 μm. If the nylon film is thinner than 10 μm, there is a concern about insufficient strength; on the other hand, if it exceeds 30 μm, it may be too rigid and unsuitable for processing. As for the nylon film, a biaxially stretched film with a stretch ratio in both longitudinal and transverse directions of typically 2 times or more, preferably around 2.5 to 4 times, is preferred.

[0118] The laminated film of the present invention also includes a configuration having the above-mentioned layers other than the capping layer and the inorganic film layer.

[0119] Example

[0120] The following examples illustrate the invention in more detail, but the invention is not limited to these examples and may be implemented with appropriate modifications within the scope suitable for the foregoing / hereafter described in the spirit of the invention. It should be noted that, unless otherwise specified, "%" refers to "percentage by mass" and "parts" refers to "parts by mass".

[0121] The evaluation methods and property measurement methods used in each embodiment and comparative example are described below.

[0122] (1) Evaluation of the fabrication of laminated laminates

[0123] Using a urethane-based two-component curable adhesive (a mixture of "TAKELAC (registered trademark) A525S" and "TAKENATE (registered trademark) A50" manufactured by Mitsui Chemicals Co., Ltd. in a 13.5:1 (mass ratio) ratio), an unstretched polypropylene film ("P1147" manufactured by Toyobo Co., Ltd.) with a thickness of 70 μm as a heat-sealing resin layer was laminated onto the protective layer side (or vapor-deposited layer side in the absence of a protective layer) of each laminated film obtained in the Examples and Comparative Examples, and cured at 40°C for 4 days, thereby obtaining a laminated gas barrier laminate for evaluation (hereinafter sometimes referred to as "laminated laminate"). It should be noted that the thickness of the adhesive layer formed by the urethane-based two-component curable adhesive after drying was adjusted to approximately 2 μm or 5 μm by adjusting the concentration.

[0124] (2) Evaluation method of oxygen permeability

[0125] For each of the obtained laminated films, the oxygen permeability under normal conditions was measured using an oxygen permeability measuring device (MOCON "OX-TRAN2 / 20") according to the electrolytic sensor method of JIS-K7126-2 (Appendix A) at 23°C and 65% relative humidity. It should be noted that the oxygen permeability measurement was performed in the direction in which oxygen permeates from the substrate film side without the laminated capping / protective layer to the capping / protective layer side.

[0126] On the other hand, the laminate prepared in (1) above was subjected to a wet heat treatment in hot water at 130°C for 30 minutes and dried at 40°C for 1 day (24 hours). The resulting wet heat-treated laminate was subjected to the same operation as above, and the oxygen permeability (after cooking) was measured.

[0127] (3) Evaluation method of lamination strength

[0128] The laminate prepared in (1) above was subjected to a hygrothermal treatment in hot water at 130°C for 30 minutes. While still undried, it was cut into test pieces with a width of 15 mm and a length of 200 mm. The lamination strength (after cooking) was measured using a TENSILON universal testing machine (Toyo Baldwin Co., Ltd. "TENSILONUMT-II-500") at a temperature of 23°C and a relative humidity of 65%. The lamination strength was defined as the strength obtained when peeling at a tensile speed of 200 mm / min and a peel angle of 90 degrees.

[0129] (4) Method for determining the arithmetic mean roughness of the protective layer

[0130] The arithmetic mean roughness of the protective layer was measured using a scanning probe microscope (SPM) (Shimadzu Corporation "SPM9700") (cantilever: OMCL-AC200TS provided by Olympus Corporation, observation mode: phase mode). Specifically, SPM images were obtained at a 2 μm square viewing angle on the surface of the coating layer. The arithmetic mean roughness value was calculated after slope correction in the X, Y, and Z directions using the slope correction function of the software included with the SPM.

[0131] (5) Method for determining the surface hardness of the protective layer

[0132] The surface hardness of the protective layer was measured using a dynamic microhardness tester ("DUH-211" manufactured by Shimadzu Corporation). Specifically, for individual protective layers of laminated films held in place on a glass plate by adhesive, a hardness test was performed using a 115° diamond triangular pyramid indenter (Berkovich type) under load and unload conditions. The obtained Martens hardness was taken as the surface hardness value. The test conditions were: test force 0.1 mN, load speed 0.02 mN / s, and holding time 2 seconds.

[0133] (6) Evaluation method for the printability of thin films

[0134] For each of the resulting laminated films, a 2μm printing layer was laminated using solvent-based ink (Rio-alpha (registered trademark) R641 white, manufactured by Toyo Ink). The printed layer was wiped 5 times with a cotton swab, and cases of no ink peeling were recorded as "closed" (○), partial peeling as "closed" (△), and peeling of the entire surface as "closed" (×). Regarding ink transferability, halftone printing was performed using the aforementioned ink at a concentration of 60%. When the surface of the printed layer was observed under an optical microscope at ×50 magnification, cases where the ink was connected to form a network were recorded as "transferability" (○), cases where some ink was not connected were recorded as "transferability" (△), and cases where the ink was completely unconnected and formed dots were recorded as "transferability" (×).

[0135] (7) Method for measuring the adhesion amount of protective layer

[0136] In each embodiment and comparative example, each laminated film obtained in the stage of laminating the protective layer on the substrate film is used as a sample. A 100mm×100mm test piece is cut from the sample, and the protective layer is wiped with 1-methoxy-2-propanol or dimethylformamide. The adhesion amount is calculated from the mass change of the film before and after wiping.

[0137] (8) The amount of oxazoline groups in resins containing oxazoline groups

[0138] The resin containing oxazoline was freeze-dried and analyzed using a Varian Gemini-200 nuclear magnetic resonance (NMR) analyzer. 1 ¹H-NMR spectra were used to determine the absorption peak intensities originating from the oxazoline group and those originating from other monomers, and the amount of oxazoline group (mmol / g) was calculated from these peak intensities.

[0139] (9) Quantitative method for isocyanate components in polyurethane resin

[0140] The sample was dried under reduced pressure and measured using a Varian Gemini-200 nuclear magnetic resonance (NMR) analyzer. 1 H-NMR spectra, the molar percentage of isocyanate components is determined by the integral ratio of peak intensities originating from each isocyanate component.

[0141] In each embodiment and comparative example, the materials used in the formation of the cover layer and the protective layer are prepared as follows.

[0142] <Preparation of materials used in the formation of the capping or protective layer>

[0143] [Resin with oxazoline group (A)]

[0144] As a resin containing an oxazoline group, a commercially available water-soluble oxazoline-containing acrylate (manufactured by Nippon Shokubai Co., Ltd., "EPOCROS (registered trademark) WS-300"; solids content 10%) is prepared. The oxazoline group content of this resin is 7.7 mmol / g.

[0145] [Acrylic Resin (B)]

[0146] As an acrylic resin, a 25% by weight emulsion of an acrylate copolymer (manufactured by Nichigo-Mowinyl Co., Ltd., "Mowinyl (registered trademark) 7980") is prepared for commercial use. The acid value (theoretical value) of this acrylic resin (B) is 4 mg KOH / g.

[0147] [Polyurethane Resin (C)]

[0148] As a polyurethane resin, a commercially available dispersion of polyester polyurethane resin (Mitsui Chemicals, Ltd., "TAKELAC (registered trademark) W605"; solids content 30%) is prepared. This polyurethane resin has an acid value of 25 mg KOH / g and a glass transition temperature (Tg) of 100°C as determined by DSC. Furthermore, through… 1 The proportion of aromatic or aromatic aliphatic diisocyanate to the total polyisocyanate component, as determined by H-NMR, was 55 mol.

[0149] [Polyurethane Resin (D1)]

[0150] As a polyurethane resin, a commercially available dispersion of a polyurethane resin containing isophthalic acid (Mitsui Chemicals, Ltd., "TAKELAC (registered trademark) WPB341"; solids content 30%) is prepared. This polyurethane resin has an acid value of 25 mg KOH / g and a glass transition temperature (Tg) of 130°C as determined by DSC. Furthermore, through… 1 The proportion of aromatic or aromatic aliphatic diisocyanate to the total polyisocyanate component, as determined by H-NMR, was 85 mol.

[0151] [Polyurethane Resin (D2)]

[0152] As a polyurethane resin, a commercially available dispersion of polycarbonate polyurethane resin (Mitsui Chemicals, Ltd., "TAKELAC (registered trademark) WS4000"; solids content 30%) is prepared. The glass transition temperature (Tg) of this polyurethane resin, as determined by DSC, is 130°C.

[0153] [Polyurethane Resin (D3)]

[0154] As a polyurethane resin, a commercially available dispersion of polyester polyurethane resin (Mitsui Chemicals, Ltd., "TAKELAC (registered trademark) WS4022"; solids content 30%) is prepared. The glass transition temperature (Tg) of this polyurethane resin, as determined by DSC, is 110°C.

[0155] [Silane Coupling Agent (G)]

[0156] As a silane coupling agent, Shin-Etsu Chemical Co., Ltd.'s "(registered trademark) KBM603" (30% solid content) is prepared for commercial use.

[0157] [Gas-barrier vinyl alcohol resin (H)]

[0158] As a vinyl alcohol resin with gas barrier properties, a commercially available water-soluble vinyl alcohol resin ("Nichigo G-Polymer (registered trademark) OKS-8049"; powder, manufactured by Nippon Synthetic Chemicals Co., Ltd.) was dissolved in water to prepare an aqueous solution with a solid content of 5%.

[0159] [Gas Barrier Protective Layer Solution (I)]

[0160] A solution containing tetraethoxysilane hydrolyzed in 0.02 mol / L hydrochloric acid was added to a 5% by weight aqueous solution of polyvinyl alcohol resin (PVA) with a saponification degree of 99% and a polymerization degree of 2400, at a weight ratio of SiO2 / PVA = 60 / 40, as a gas barrier protective layer solution (I).

[0161] Example 1

[0162] (1) Preparation of coating liquid 1 used in the cover layer

[0163] The materials are mixed according to the following mixing ratios to prepare a coating liquid (resin composition for the coating layer). It should be noted that the mass conversions of the solid components of the oxazoline-containing resin (A), acrylic resin (B), and polyurethane resin (C) in the resulting coating liquid are shown in Table 1.

[0164] Water: 54.40%

[0165] Isopropanol: 25.00%

[0166] Oxazoline-containing resin (A): 15.00%

[0167] Acrylic resin (B): 3.60%

[0168] Polyurethane resin (C): 2.00%

[0169] (2) Preparation of coating liquid 2 used in the coating of the protective layer

[0170] Mix the following coating agents to prepare coating solution 2. The mass conversion of the solid components of the polyurethane resin (D1) is shown in Table 1.

[0171] Water 58.33%

[0172] Isopropanol 30.00%

[0173] Polyurethane resin (D1) 11.67%

[0174] (3) Manufacturing of polyester substrate film and coating of coating liquid 1 (lamination of cover layer)

[0175] Polyethylene terephthalate resin with an intrinsic viscosity of 0.62 dl / g (30°C, phenol / tetrachloroethane = 60 / 40) was pre-crystallized and then formally dried. Extrusion was performed at 280°C using an extruder with a T-die, followed by rapid curing on a roller with a surface temperature of 40°C to obtain an amorphous sheet. The resulting sheet was then stretched 4.0 times longitudinally at 100°C between heated and cooled rollers. The coating solution 1 was then applied to one side of the resulting uniaxially stretched film using a fountain coating method. While drying, the film was fed into a tenter frame, preheated at 100°C, stretched 4.0 times transversely at 120°C, and subjected to a 6% transverse relaxation while undergoing heat treatment at 225°C to obtain a 12 μm thick biaxially stretched polyester film with a 0.020 g / m² coating. 2 The layered thin film covering the coating.

[0176] (4) Formation of inorganic thin film layer (evaporation)

[0177] Next, a composite inorganic oxide layer of silicon dioxide and aluminum oxide is formed on the capping layer of the laminated thin film obtained in (2) above by electron beam evaporation as an inorganic thin film layer. As the evaporation source, granular SiO2 (99.9% purity) and Al2O3 (99.9% purity) of approximately 3 mm to 5 mm are used. The composition of the composite oxide layer here is SiO2 / Al2O3 (mass ratio) = 60 / 40. Furthermore, the thickness of the inorganic thin film layer (SiO2 / Al2O3 composite oxide layer) is 13 nm.

[0178] (5) Coating of coating solution 2 on the vapor-deposited thin film (layering of protective layer)

[0179] Coating solution 2 was applied to the inorganic film layer of the vapor-deposited film obtained in (4) using a wire rod coating method, and dried at 200°C for 15 seconds to obtain a protective layer. The coating weight after drying was 0.210 g / m². 2 (dry).

[0180] As described above, a laminated film having a capping layer / metal oxide layer / protective layer on a substrate film was fabricated. The resulting laminated film was evaluated for oxygen permeability, lamination strength, and printability as described above. The results are shown in Table 1.

[0181] (Examples 2-7, Comparative Examples 1-6)

[0182] When preparing the coating liquid for forming the protective layer, the resin mixing amount, adhesion amount, and type were changed as shown in Table 1. Otherwise, the laminated films were prepared in the same manner as in Example 1, and the oxygen permeability, lamination strength, and printability were evaluated. The results are shown in Table 1.

[0183] [Table 1]

[0184]

[0185] Industrial applicability

[0186] According to the present invention, a gas-barrier laminated film can be provided, which exhibits excellent gas barrier properties under normal conditions and after undergoing hydrothermal treatment, while also possessing excellent adhesion independent of adhesive thickness, and further providing sufficient adhesion and transferability of ink during printing. This gas-barrier laminated film has the advantages of being easy to manufacture, economical, having excellent production stability, and readily obtainable homogeneous properties. Furthermore, due to its excellent adhesion, the thickness of the adhesive can be reduced, thus greatly benefiting the safety / hygiene and economic (cost) aspects of processing. Therefore, this gas-barrier laminated film is not limited to food packaging for hydrothermal treatment; in addition to its use in packaging various foods, pharmaceuticals, and industrial products, it can also be widely used in industrial applications such as solar cells, electronic paper, organic EL components, and semiconductor components.

Claims

1. A laminated thin film, characterized in that, The substrate film has a cover layer on at least one side, the cover layer being formed of a cover layer resin composition comprising a resin having an oxazoline group as a component, an inorganic film layer being formed on the cover layer, and a protective layer containing a polyurethane resin being formed on the inorganic film layer, the surface hardness of the protective layer of the laminated film being 350 to 700 N / mm. 2 Furthermore, the arithmetic mean roughness of the 2μm square section of the protective layer is 0.5–2.0 nm. The glass transition temperature of the polyurethane resin contained in the protective layer is above 130°C. The acid value of the polyurethane resin contained in the protective layer is in the range of 20 to 55 mg KOH / g.

2. The laminated film according to claim 1, characterized in that, The polyurethane resin contained in the protective layer contains aromatic or aromatic aliphatic components.

3. The laminated film according to claim 1, characterized in that, The polyurethane resin contained in the protective layer contains isophthalic diisocyanate.

4. The laminated film according to claim 1, characterized in that, The amount of oxazoline groups in the resin composition for the coating layer is 5.1 to 9.0 mmol / g.

5. The laminated film according to claim 1, characterized in that, The coating layer contains acrylic resin with an acid value of less than 10 mg KOH / g.

6. The laminated film according to any one of claims 1 to 5, characterized in that, The inorganic thin film layer is a composite oxide layer of silicon oxide and aluminum oxide.

Images