Laminated film, laminate and packaging

Abstract

To solve the following problems in which: there are various vapor deposition films different in heat shrinkability depending on base films thereof; using a vapor deposition film with a high thermal shrinkage in its longitudinal direction to make a laminate for retort processing may cause a deterioration of its barrier properties; and improving the trouble by a change to the base film requires setting a specific brand because of the large production volume at one time.SOLUTION: The present invention provides a multilayer body which has a shrinkage in the MD direction of 1.2% or less before and after retort processing in the width direction, with the difference ▵ between the maximum MD shrinkage and the minimum MD shrinkage being 0.4% or less in the width direction, so that the water vapor transmission after retort processing can be kept under 2.5 g / m2 day.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a laminate film used in the packaging fields of foods, pharmaceuticals, industrial products, etc. More specifically, the present invention relates to a gas barrier laminate film having an inorganic thin film layer, which can exhibit good gas barrier properties and adhesion by controlling the physical properties of the film. [Background technology]

[0002] Packaging materials used for food, pharmaceuticals, etc. are required to have gas barrier properties, i.e., the ability to block gases such as oxygen and water vapor, in order to prevent oxidation of proteins and fats, preserve flavor and freshness, and maintain the efficacy of pharmaceuticals. Furthermore, gas barrier materials used in electronic devices and components such as solar cells and organic electroluminescence (EL) devices require even higher gas barrier properties than packaging materials for food, etc.

[0003] Conventionally, in food applications that require blocking various gases such as water vapor and oxygen, gas barrier laminate films have generally been used, in which a thin metal film made of aluminum or the like or a thin inorganic film made of an inorganic oxide such as silicon oxide or aluminum oxide is formed on the surface of a plastic substrate film. In particular, films formed with a thin film of an inorganic oxide such as silicon oxide, aluminum oxide, or a mixture thereof are widely used because they are transparent and allow the contents to be confirmed.

[0004] However, inorganic thin films have poor flexibility, and therefore pinholes and defects are likely to occur when the film is bent or subjected to impact, or when the film is subjected to high-temperature treatment such as retort treatment, resulting in problems such as a decrease in gas barrier properties.

[0005] To address the above-mentioned problems, attempts have been made to provide an additional protective layer on the inorganic thin film. For example, a laminated film in which a water-soluble polymer resin or a solvent-soluble resin is provided on an inorganic thin film is known, which can improve the stability of the gas barrier property.

[0006] However, these laminated films have various heat shrinkage rates depending on the position of the base film and the winding conditions when laminating the inorganic thin film. When a laminated product is made by laminating a sealant layer using a laminated film with a high heat shrinkage rate and then undergoing retort processing, the laminate expands and contracts during high-humidity heat treatment, causing tensile and compressive stresses in the gas barrier layer, resulting in cracks and a decrease in barrier performance.

[0007] Against this background, a method is known in which a coating layer such as an in-line coating layer or an anchor coating layer is applied to a base film, thereby maintaining gas barrier properties and adhesion even after wet heat treatment (Patent Documents 1 and 2). A method is also known in which a base film containing a polyester resin whose main constituent unit is butylene terephthalate units is used to improve the flexibility of the base material itself, thereby maintaining good gas barrier properties even after wet heat treatment (Patent Documents 3 and 4). Another method is known in which a laminated film of shrink film and polyamide film is used to adjust the shrinkage rate, thereby maintaining good gas barrier properties even after hot water treatment (Patent Document 5).

[0008] However, with any of the above methods, it is necessary to change the raw material of the base film itself, and a dedicated lot must be prepared, which poses the problem of not being able to handle high-mix, small-lot production.

[0009] Furthermore, a method is known in which the thermal shrinkage rate can be controlled by the drying process of the substrate, thereby improving the interlayer adhesion strength (Patent Document 6). However, there is no mention of moist heat treatment.

[0010] Furthermore, when a wide laminated film is made, there is a problem that, due to the difference in the thermal shrinkage rate in the width direction caused by the base film, pinholes and defects occur in the inorganic thin film when subjected to high-temperature treatment such as retort treatment, thereby reducing the gas barrier property. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Patent No. 6631098 [Patent Document 2] Patent No. 6507847 [Patent Document 3] Japanese Patent Publication No. 2019-014043 [Patent Document 4] Patent No. 6879292 [Patent Document 5] JP 2018-089800 A [Patent Document 6] Japanese Patent Application Laid-Open No. 2017-144593 Summary of the Invention [Problem to be solved by the invention]

[0012] An object of the present invention is to provide a laminate film that has good gas barrier properties even when it is wide, and that has little variation in gas barrier properties in the width direction even after retort treatment. [Means for solving the problem]

[0013] The inventors have discovered that by maintaining the film surface temperature at or above the retort treatment temperature and controlling the tension during the protective layer coating process, it is possible to produce a laminated film that has a desired heat shrinkage rate at the end of coating, and further, to maintain its gas barrier properties when subjected to retort treatment.

[0014] That is, the present invention comprises the following configurations. (1) A laminated film having gas barrier properties, comprising a resin substrate, an inorganic thin film layer laminated on at least one side of the resin substrate, and a protective layer laminated on the inorganic thin film layer, and characterized in that the film satisfies the following requirements (I) to (III): (I) No layer is provided between the resin substrate and the inorganic thin film layer. (II) The thermal shrinkage rate in the MD direction before and after retort treatment at 130°C for 30 minutes is 1.2% or less. (III) A 15 μm biaxially oriented nylon film and a 70 μm unoriented polypropylene film are applied to the surface of the protective layer of the laminated film by a polyurethane-based two-component curing adhesive so that the thickness after drying is 4 μm, and then laminated by a dry lamination method. After aging at a temperature of 40°C for 4 days and then subjected to a wet heat treatment at 130°C for 30 minutes, the water vapor permeability is 2.5 g / m 2 - Must be within 1 day. (2) The laminated film according to (1), wherein the laminated film has a width of 1,000 mm or more and the difference Δ between the maximum MD shrinkage rate and the minimum MD shrinkage rate in the width direction when retorted at 130°C for 30 minutes is within 0.4%. (3) The laminated film according to (1) or (2), wherein the inorganic thin film layer contains at least one inorganic oxide containing silicon oxide and / or aluminum oxide. (4) The laminated film according to any one of (1) to (3), wherein the protective layer contains at least one type of urethane resin or ester resin. (5) The laminated film according to any one of (1) to (4), wherein the protective layer contains a silane coupling agent. (6) A laminate obtained by laminating a heat seal layer on the surface of the protective layer of the laminate film according to any one of (1) to (5) above. (7) A packaging bag characterized in that the laminate described in (6) above is used in at least a part thereof. [Effects of the Invention]

[0015] According to the present invention, it is possible to obtain a wide laminate film that has good gas barrier properties and also has a desired heat shrinkage rate at the end of coating, and even when subjected to retort treatment, it is possible to maintain good gas barrier properties with little variation in gas barrier properties in the width direction. DETAILED DESCRIPTION OF THE INVENTION

[0016] The laminated film of the present invention is a laminated film having gas barrier properties, comprising a resin substrate, an inorganic thin film layer laminated on at least one side of the resin substrate, and a protective layer laminated on the inorganic thin film layer, wherein the difference Δ between the maximum MD shrinkage rate and the minimum MD shrinkage rate in the film width direction during retort treatment at 130°C for 30 minutes is within 0.4%, and wherein a 15 μm biaxially oriented nylon film and a 70 μm unoriented polypropylene film are coated on the surface of the protective layer of the laminated film with a polyurethane-based two-component curing adhesive so that the thickness after drying is 4 μm, and the laminate is laminated by a dry lamination method to form a laminate, which is then aged at a temperature of 40°C for 4 days and then subjected to a wet heat treatment at 130°C for 30 minutes, and has a maximum water vapor permeability in the width direction of 2.5 g / m 2 First, we will explain the plastic substrate film, then we will explain the inorganic thin film layer and protective layer laminated on it, and further the other layers.

[0017] [Base film] The substrate film (hereinafter sometimes referred to as "substrate film") used in the present invention may be, for example, a stretched film obtained by melt-extruding a plastic and, if necessary, stretching it in the machine direction (MD) and / or the width direction (TD), cooling, and heat setting. Biaxially stretched films stretched in both the machine direction and the width direction are preferred in terms of obtaining sufficient mechanical strength. 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-naphthalate; polyolefins such as polyethylene, polypropylene, and polybutene; as well as polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, wholly aromatic polyamides, polyamideimides, polyimides, polyetherimides, polysulfones, polystyrenes, and polylactic acids. Among these, polyesters are preferred in terms of heat resistance, dimensional stability, and transparency, and polyethylene terephthalate and copolymers of polyethylene terephthalate with other components are particularly preferred.

[0018] The substrate film can have any thickness depending on the desired purpose and application, such as mechanical strength and transparency. While the thickness is not particularly limited, a thickness of 5 to 250 μm is generally recommended, and 10 to 60 μm is desirable when used as a packaging material. From the viewpoints of handling during processing, post-processing, and machine costs, the width of the substrate film is preferably 1,000 mm or more and 5,000 mm or less, more preferably 3,000 mm or less, and even more preferably 2,000 mm or less. The transparency of the substrate film is not particularly limited, but when used as a packaging material requiring transparency, a light transmittance of 50% or more is desirable.

[0019] The substrate film may be a monolayer film made of one type of plastic, or a laminated film in which two or more types of plastic films are laminated. When a laminated film is used, the type of laminated film, the number of layers, the lamination method, etc. are not particularly limited, and can be arbitrarily selected from known methods depending on the purpose. Furthermore, the substrate film may be subjected to surface treatment such as corona discharge treatment, glow discharge, flame treatment, surface roughening treatment, etc., as long as it does not impair the purpose of the present invention, and may also be subjected to known anchor coating treatment, printing, decoration, etc.

[0020] The MD shrinkage rate is the shrinkage rate in the machine direction, i.e., the longitudinal direction, and the TD shrinkage rate is the shrinkage rate in the transverse direction, i.e., the horizontal direction.

[0021] The initial MD heat shrinkage of the substrate film used before and after 30 minutes of retort treatment at 130°C must be 1.6% or less, preferably 1.5% or less, and more preferably 1.4% or less. The widthwise MD heat shrinkage difference Δ is preferably 0.6% or less, more preferably 0.5% or less, and even more preferably 0.4% or less. The TD heat shrinkage is preferably -0.6% or more, more preferably -0.5% or more, and even more preferably -0.4% or more.

[0022] [Inorganic thin film layer] The laminated film of the present invention has an inorganic thin film layer on the substrate film, which is laminated directly on the resin substrate, with no intervening layer.

[0023] The inorganic thin film layer is a thin film made of a metal or inorganic oxide. There are no particular limitations on the material forming the inorganic thin film layer as long as it can be formed into a thin film. However, from the viewpoint of gas barrier properties, inorganic oxides such as aluminum oxide (alumina), silicon oxide (silica), and a mixture of silicon oxide and aluminum oxide are preferred. Aluminum oxide is particularly preferred from the viewpoint of productivity. Furthermore, a laminate film having a configuration in which a predetermined protective layer described below is combined with an inorganic thin film layer made of aluminum oxide is preferred because it exhibits significant improvements in oxygen permeability and water-lamination strength, particularly after acid treatment. Here, silicon oxide refers to various silicon oxides such as SiO and SiO2 or a mixture thereof, and aluminum oxide refers to various aluminum oxides such as AlO and Al2O3 or a mixture thereof.

[0024] The thickness of the inorganic thin film layer is usually 1 to 100 nm, preferably 3 to 50 nm, and more preferably 5 to 20 nm. If the thickness of the inorganic thin film layer is less than 1 nm, it may be difficult to obtain satisfactory gas barrier properties, while if the thickness is excessively greater than 100 nm, the corresponding improvement in gas barrier properties cannot be obtained and is actually disadvantageous in terms of flex resistance and production costs.

[0025] The method for forming the inorganic thin film layer is not particularly limited, and any known vapor deposition method, such as physical vapor deposition (PVD) methods such as vacuum deposition, sputtering, and ion plating, or chemical vapor deposition (CVD), may be appropriately employed. A typical method for forming the inorganic thin film layer will be described below, taking an aluminum oxide thin film as an example. For example, when using vacuum deposition, Al2O3 or Al is preferably used as the deposition source material. These deposition sources are typically particles, and the particle size is preferably large enough to prevent pressure changes during deposition, with a preferred particle diameter of 1 mm to 5 mm. Heating methods such as resistance heating, high-frequency induction heating, electron beam heating, and laser heating can be used. Reactive vapor deposition can also be employed, using reactive gases such as oxygen, nitrogen, hydrogen, argon, carbon dioxide, and water vapor, or by adding ozone or using ion-assisted deposition. Furthermore, film formation conditions can be freely modified, such as by applying a bias to the deposition target (the laminated film to be deposited) or by heating or cooling the deposition target. The deposition material, reactive gas, bias of the deposition target, heating / cooling, etc. can be changed in the same way when the sputtering method or the CVD method is adopted.

[0026] [Protective layer] In the present invention, a protective layer is provided on the inorganic thin film layer. The inorganic thin film layer laminated on the plastic film is not a completely dense film, but has minute defects scattered therein. By forming a protective layer by coating the inorganic thin film layer with a specific resin composition for the protective layer described below, the resin in the resin composition for the protective layer penetrates into the defects in the inorganic thin film layer, resulting in stable gas barrier properties. In addition, by using a material with gas barrier properties for the protective layer itself, the gas barrier performance of the laminate film is also greatly improved.

[0027] In the present invention, the coating amount of the protective layer is 0.05 to 0.60 g / m 2This reduces coating unevenness and defects due to uniformity, while enhancing adhesion through the anchoring effect. Furthermore, the cohesive strength of the protective layer itself is improved, strengthening adhesion between the inorganic thin film layer and the protective layer, and improving water resistance. The coating amount of the protective layer is preferably 0.08 g / m 2 More preferably, 0.10 g / m 2 More preferably, 0.15 g / m 2 or more, and preferably 0.50 g / m 2 or less, more preferably 0.45 g / m 2 or less, more preferably 0.40 g / m 2 The coating amount of the protective layer is 0.60 g / m or less. 2 If the thickness of the protective layer exceeds 0.10 g / m, the gas barrier properties will improve, but the cohesive force inside the protective layer will be insufficient, which may result in poor adhesion. Furthermore, unevenness or defects may occur in the coating appearance, and the gas barrier properties and adhesiveness may not be fully realized after moist heat treatment. On the other hand, if the thickness of the protective layer exceeds 0.10 g / m, 2 If the thickness is less than this, there is a risk that sufficient gas barrier properties, interlayer adhesion, and ink permeability may not be obtained.

[0028] The protective layer may be made of either a solvent-dispersed resin or a water-dispersed resin. Solvent-dispersed resins are particularly preferred for improving adhesion to the inorganic thin film layer. Furthermore, resins made of a polyester polyol component obtained by reacting a dicarboxylic acid with a polyhydric alcohol and a polyisocyanate component are preferred for achieving high gas barrier properties.

[0029] (A) Polyester component The polyester component is obtained by reacting a polycarboxylic acid with a polyhydric alcohol.

[0030] The polycarboxylic acid includes aromatic polycarboxylic acids, alicyclic polycarboxylic acids, aliphatic polycarboxylic acids, etc. From the viewpoint of gas barrier properties, aromatic polycarboxylic acids are preferred. Examples thereof include orthophthalic acid, isophthalic acid, terephthalic acid, 1,2-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, anthracene-1,2-dicarboxylic acid, and anthraquinone-2,3-dicarboxylic acid.

[0031] As the polyhydric alcohol, glycols ranging from low molecular weight to high molecular weight can be used. However, from the viewpoint of gas barrier properties and flexibility due to the amorphous portion, linear or branched C alkylene glycols such as ethylene glycol, propylene glycol, trimethylene glycol, 1,3-butanediol, 1,4-butanediol, pentanediol, hexanediol, neopentyl glycol, heptanediol, and octanediol are preferred. 2-10 Alkylene glycol), (poly)oxy C 2-4 Low molecular weight glycols such as alkylene glycols (diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, etc.) are used. The preferred glycol component is C 2-8 Polyol component [e.g., C 2-6 Alkylene glycol (especially ethylene glycol, 1,2- or 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, etc.), di- or tri-oxy C 2-3 Alkylene glycols (diethylene glycol, triethylene glycol, dipropylene glycol, etc.), and particularly preferred diol components are C 2-8 Alkylene glycol (especially C 2-6 alkylene glycol).

[0032] These diol components can be used alone or in combination of two or more. Furthermore, if necessary, low-molecular-weight diol components such as aromatic diols (e.g., bisphenol A, bishydroxyethyl terephthalate, catechol, resorcinol, hydroquinone, 1,3- or 1,4-xylylenediol or a mixture thereof) and alicyclic diols (e.g., hydrogenated bisphenol A, xylylenediol, cyclohexanediol, cyclohexanedimethanol) may be used in combination. Furthermore, if necessary, tri- or higher-functional polyol components, such as glycerin, trimethylolethane, trimethylolpropane, polyester polyol, polycarbonate polyol, and polyether polyol may also be used in combination. The polyol component should preferably be at least C 2-8 Polyol component (especially C 2-6 Preferably, the solvent contains alkylene glycol.

[0033] (B) Polyisocyanate component The polyisocyanate component includes aromatic polyisocyanate, alicyclic polyisocyanate, aliphatic polyisocyanate, etc. As the polyisocyanate compound, a diisocyanate compound is usually used.

[0034] Examples of aromatic diisocyanates include tolylene diisocyanate (2,4- or 2,6-tolylene diisocyanate or a mixture thereof) (TDI), phenylene diisocyanate (m-, p-phenylene diisocyanate or a mixture thereof), 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate (NDI), diphenylmethane diisocyanate (4,4'-, 2,4'-, or 2,2'-diphenylmethane diisocyanate or a mixture thereof) (MDI), 4,4'-toluidine diisocyanate (TODI), and 4,4'-diphenyl ether diisocyanate. Examples of aromatic aliphatic diisocyanates include xylylene diisocyanate (1,3- or 1,4-xylylene diisocyanate or a mixture thereof) (XDI), tetramethyl xylylene diisocyanate (1,3- or 1,4-tetramethyl xylylene diisocyanate or a mixture thereof) (TMXDI), and ω,ω'-diisocyanato-1,4-diethylbenzene.

[0035] Examples of alicyclic diisocyanates include 1,3-cyclopentene diisocyanate, cyclohexane diisocyanate (1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate), 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (isophorodiisocyanate, IPDI), methylene bis(cyclohexyl isocyanate) (4,4'-, 2,4'-, or 2,2'-methylene bis(cyclohexyl isocyanate)) (hydrogenated MDI), methyl cyclohexane diisocyanate (methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate), bis(isocyanatomethyl)cyclohexane (1,3- or 1,4-bis(isocyanatomethyl)cyclohexane or a mixture thereof) (hydrogenated XDI), and the like.

[0036] Examples of aliphatic diisocyanates include trimethylene diisocyanate, 1,2-propylene diisocyanate, butylene diisocyanate (tetramethylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate), hexamethylene diisocyanate, pendamethylene diisocyanate, 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, and 2,6-diisocyanate methyl caffeate.

[0037] A urethane resin is obtained by reacting a polyester component (A) with a polyisocyanate component (B). The weight ratio of the polyester component to the polyisocyanate component is 9:1 to 1:9 in terms of solid content, preferably 8:2 to 2:8, and more preferably 6:4 to 4:6.

[0038] The resin composition for a protective layer of the present invention preferably contains a silane coupling agent as described below, but may also contain various additives as needed within a range that does not impair the gas barrier properties. Examples of additives include layered inorganic compounds, stabilizers (antioxidants, heat stabilizers, ultraviolet absorbers, etc.), plasticizers, antistatic agents, lubricants, antiblocking agents, colorants, fillers, and crystal nucleating agents.

[0039] Silane coupling agents are effective in improving the adhesion of a protective layer to an inorganic thin film layer. Examples of silane coupling agents include hydrolyzable alkoxysilane compounds, such as halogen-containing alkoxysilanes (e.g., chloro C2-4 alkyl tri C1-4 alkoxysilanes such as 2-chloroethyltrimethoxysilane, 2-chloroethyltriethoxysilane, 3-chloropropyltrimethoxysilane, and 3-chloropropyltriethoxysilane), and epoxy-containing alkoxysilanes (e.g., 2-glycidyloxyethyltrimethoxysilane, 2-glycidyloxyethyltriethoxysilane, and 3-glycidyloxypropyltriethoxysilane). trimethoxysilane, glycidyloxy C2-4 alkyltriC1-4 alkoxysilanes such as 3-glycidyloxypropyltriethoxysilane, glycidyloxydiC2-4 alkyldiC1-4 alkoxysilanes such as 3-glycidyloxypropylmethyldimethoxysilane and 3-glycidyloxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 3-(3,4-epoxycyclohexyl)propyl (epoxycycloalkyl)C2-4 alkyltriC1-4 alkoxysilanes such as 2-aminoethyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, etc.], alkoxysilanes having an amino group [aminoC2-4 alkyltriC1-4 alkoxysilanes such as 2-aminoethyltrimethoxysilane, 3-aminopropyltriethoxysilane, etc., aminodiC2-4 alkyldiC1-4 alkoxysilanes such as 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, etc., 2-[N-(2-aminoethyl)amino] (2-aminoC2-4 alkyl)aminoC2-4 alkyltriC1-4 alkoxysilanes such as 3-[N-(2-aminoethyl)amino]ethyltrimethoxysilane, 3-[N-(2-aminoethyl)amino]propyltrimethoxysilane, and 3-[N-(2-aminoethyl)amino]propyltriethoxysilane; (aminoC2-4 alkyl)aminodiC2-4 alkyldiC1-4 alkoxysilanes such as 3-[N-(2-aminoethyl)amino]propylmethyldimethoxysilane and 3-[N-(2-aminoethyl)amino]propylmethyldiethoxysilane;Alkoxysilanes having a mercapto group (mercapto C2-4 alkyltri C1-4 alkoxysilanes such as 2-mercaptoethyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, etc., mercaptodi C2-4 alkyldi C1-4 alkoxysilanes such as 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropylmethyldiethoxysilane, etc.), alkoxysilanes having a vinyl group (vinyltri C1-4 alkoxysilanes such as vinyltrimethoxysilane, vinyltriethoxysilane, etc.), ethylene Examples of suitable silane coupling agents include alkoxysilanes having a hydrolytically unsaturated bond group [(meth)acryloxyC2-4 alkyltriC1-4 alkoxysilanes such as 2-(meth)acryloxyethyltrimethoxysilane, 2-(meth)acryloxyethyltriethoxysilane, 3-(meth)acryloxypropyltrimethoxysilane, and 3-(meth)acryloxypropyltriethoxysilane, and (meth)acryloxydiC2-4 alkyldiC1-4 alkoxysilanes such as 3-(meth)acryloxypropylmethyldimethoxysilane and 3-(meth)acryloxypropylmethyldiethoxysilane, etc.]. Among the above-mentioned silane coupling agents, alkoxysilane compounds having an amino group are preferred, with aminopropyltrimethoxysilane being particularly preferred. These silane coupling agents can be used alone or in combination.

[0040] The content of the silane coupling agent is 5.0% by weight or less, preferably 2.0 to 4.5% by weight, and more preferably about 3.0 to 4.0% by weight, based on the protective layer.

[0041] When forming a protective layer using a resin composition for a protective layer, a coating liquid (coating liquid) containing the composition and an organic solvent is prepared, applied to a substrate film, and dried. The organic solvent can be selected from alcohols such as methanol, ethanol, and isopropyl alcohol (IPA), ketones such as acetone and methyl ethyl ketone, ethers such as propylene glycol monomethyl ether and propylene glycol monomethyl ether acetate, and esters such as ethyl acetate and propyl acetate, either alone or in combination. From the viewpoints of coating film processing and odor, methyl ethyl ketone and ethyl acetate are preferred.

[0042] The coating method of the resin composition for the protective layer is not particularly limited as long as it is a method that coats the film surface to form a layer. For example, conventional coating methods such as gravure coating, reverse roll coating, wire bar coating, and die coating can be used. From the viewpoints of productivity and coating stability, wire bar coating and gravure coating are preferably used. In the present invention, by adopting specific process conditions when coating and drying the protective layer as described below, it is possible to obtain a predetermined heat shrinkage rate in the laminated film and reduce the variation in the heat shrinkage rate in the width direction.

[0043] When forming a protective layer, it is preferable to apply a resin composition for the protective layer and then heat-dry it. The drying temperature is preferably 110 to 210°C, more preferably 115 to 205°C, and even more preferably 120 to 200°C. Drying temperatures below 110°C can result in insufficient drying or heat-induced cohesion of the protective layer, potentially resulting in a surface hardness outside the specified range. This can result in reduced adhesion and water resistance of the protective layer when subjected to boiling or retort treatment. On the other hand, drying temperatures above 210°C can result in excessive cohesion of the protective layer, resulting in film hardness and destruction of the barrier layer, potentially resulting in reduced barrier performance. Furthermore, excessive heat applied to the film substrate itself can cause the film to become brittle or shrink, potentially resulting in poor processability. In addition to drying, additional heat treatment (e.g., 150 to 190°C) can also be effective in accelerating the drying of the protective layer.

[0044] The drying time for the protective layer is preferably 30 seconds or less. If the drying time exceeds 30 seconds, not only will the protective layer not dry, but the base film will shrink, causing cracks in the gas barrier layer and a decrease in gas barrier performance. On the other hand, if the drying time is shorter than 5 seconds, the protective layer will not harden, resulting in a decrease in adhesion and barrier properties. From the viewpoint of productivity, the drying time is more preferably 5 to 25 seconds, and even more preferably 10 to 20 seconds. If the film is heated too quickly, the film will shrink significantly, causing compressive stress in the gas barrier layer and a decrease in barrier performance. It is preferable to increase the temperature at a rate of 50°C / second or less. More preferably, the drying time is 30°C / second or less, and even more preferably, 20°C / second or less.

[0045] The surface temperature during heating in the step of forming the protective layer is preferably 100 to 150°C, more preferably 105 to 145°C, and even more preferably 110 to 140°C.

[0046] The film tension during heating in the step of forming the protective layer is preferably 30 to 90 N / m, more preferably 40 to 80 N / m, and even more preferably 50 to 70 N / m. If it is less than 20 N / m, poor winding occurs, and if it exceeds 100 N / m, tensile stress is generated in the gas barrier layer, reducing the barrier performance.

[0047] The MD heat shrinkage of the laminated film before and after retorting at 130°C for 30 minutes must be 0.0% to 1.2%, preferably 0.1% to 1.1%, more preferably 0.2% to 1.0%, and even more preferably 0.3% to 0.9%. The width direction MD heat shrinkage difference △ is preferably 0.3% or less, more preferably 0.2% or less, and even more preferably 0.1% or less. The TD heat shrinkage is preferably -0.5% to 0.4%, more preferably -0.4% to 0.3%, and even more preferably -0.3% to 0.2%.

[0048] Even if the thermal shrinkage rates of the base film having an inorganic thin film layer in the MD and TD directions vary across the width, a thermal shrinkage rate with no variation across the width can be obtained by drying the base film at a predetermined temperature and under a predetermined tension within a variation of △3°C across the width in the protective layer forming process.

[0049] [Heat seal layer] When a gas barrier laminate film having an inorganic thin film layer is used as a packaging material, it is preferable to form a heat-sealable layer called a sealant. The heat-sealable layer is usually formed on the inorganic thin film layer, but it can also be formed on the outer surface of the base film (the surface opposite the surface on which the protective layer is formed). The heat-sealable resin is usually formed by extrusion lamination or dry lamination. The thermoplastic polymer forming the heat-sealable resin layer can be any polymer that exhibits sufficient sealant adhesion, and examples of such polymers include polyethylene resins such as HDPE, LDPE, and LLDPE, polypropylene resins, ethylene-vinyl acetate copolymers, ethylene-α-olefin random copolymers, and ionomer resins. When a moist heat treatment such as retort processing is performed, it is preferable to form the heat-sealable layer using a polypropylene resin by the dry lamination method. The recommended thickness of the heat-sealable layer is usually 20 to 250 μm, and when used as a packaging material, a thickness of 40 to 100 μm is desirable.

[0050] Polyurethane resin, polyisocyanate resin, polyester resin, ether resin, etc. are used to bond the protective layer and the heat seal layer. When performing a moist heat treatment such as retort treatment, it is preferable to use a reaction product of polyurethane resin and polyisocyanate resin as the adhesive. The amount of application varies depending on the material of the film to be bonded, but is generally 1 to 20 g / m. 2 is preferable, and more preferably 2 to 10 g / m 2 and more preferably 3 to 6 g / m 2 The adhesion temperature is set depending on the thickness of the heat seal layer and the thickness of the adhesive, but is preferably 50 to 120°C, more preferably 55 to 100°C, and even more preferably 60 to 80°C.

[0051] As described above, the laminate film of the present invention is a gas barrier laminate film (laminate film) that has excellent water vapor barrier properties and appearance both in its normal state and after retort treatment, and has good adhesion even when processed by printing, lamination, etc., and is easy to produce and economical.

[0052] [Other layers] In addition to the above-mentioned base film, inorganic thin film layer, and protective layer, the gas barrier laminate film having an inorganic thin film layer formed using the laminate film of the present invention may also have various layers, as necessary, that are included in known gas barrier laminate films. For example, a polyamide resin may be provided as an intermediate layer between the gas barrier laminate film and the heat seal layer to improve the adhesion and flexibility of the laminate. A coating layer may also be provided to react with oxygen-deficient portions of inorganic oxides or metal hydroxides generated during the formation of the inorganic thin film layer, thereby improving adhesion.

[0053] Furthermore, the gas barrier laminate film having an inorganic thin film layer may have at least one or more printed layers or other plastic substrates and / or paper substrates laminated between or on the outside of the inorganic thin film layer or the substrate film and the heat-sealable resin layer.

[0054] As the printing ink for forming the printing layer, aqueous and solvent-based resin-containing printing inks are preferably used. Examples of resins used in printing inks include acrylic resins, urethane resins, polyester resins, vinyl chloride resins, vinyl acetate copolymer resins, and mixtures thereof. The printing ink may contain known additives such as antistatic agents, light-blocking agents, ultraviolet absorbers, plasticizers, lubricants, fillers, colorants, stabilizers, lubricants, defoamers, crosslinking agents, anti-blocking agents, and antioxidants. The printing method for forming the printing layer is not particularly limited, and known printing methods such as offset printing, gravure printing, and screen printing can be used. To dry the solvent after printing, known drying methods such as hot air drying, heat roll drying, and infrared drying can be used.

[0055] On the other hand, as other plastic substrates or paper substrates, from the viewpoint of obtaining sufficient rigidity and strength of the laminated film, paper, polyester resin, polyamide resin, biodegradable resin, etc. are preferably used. In addition, in order to obtain a film with excellent mechanical strength, stretched films such as biaxially stretched polyester film and biaxially stretched nylon film are preferred.

[0056] In particular, when a gas barrier laminate film having an inorganic thin film layer is used as a packaging material, it is preferable to laminate a nylon film between the inorganic thin film layer and the heat-sealable resin layer to improve mechanical properties such as pinhole resistance and puncture resistance. Typical types of nylon used here include nylon 6, nylon 66, and metaxylene adipamide. The nylon film typically has a thickness of 10 to 30 μm, preferably 15 to 25 μm. If the nylon film is thinner than 10 μm, it may lack strength, while if it exceeds 30 μm, it may be too stiff and unsuitable for processing. The nylon film is preferably a biaxially stretched film with a stretch ratio in both the longitudinal and transverse directions of typically 2 times or more, preferably about 2.5 to 4 times.

[0057] The laminate film of the present invention also includes an embodiment having the above-mentioned layers other than the substrate layer, inorganic thin film layer, and protective layer.

[0058] The water vapor permeability of the laminated film of the present invention is 2.5 g / m 2 1.0 g / m or less, more preferably 2.0 g / m 2 ·day or less, and more preferably 1.5 g / m 2 ·day or less. In addition, the water vapor transmission rate after retort processing is 2.5 g / m 2 1.0 g / m or less, more preferably 2.0 g / m 2 ·day or less, and more preferably 1.5 g / m 2 ·day or less. [Example]

[0059] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples and can be practiced with appropriate modifications within the scope of the above and below-described aims, all of which are included within the technical scope of the present invention. Unless otherwise specified, "%" means "% by mass."

[0060] The processing methods and evaluation and property measurement methods used in each example and comparative example are as follows.

[0061] (1) Film surface temperature measurement method The film surface temperature was measured using a thermocouple (AEROPAK sheathed thermocouple, manufactured by Okazaki Seisakusho Co., Ltd.).

[0062] (2) Preparation of laminated film for evaluation A 15 μm thick biaxially oriented nylon film (Toyobo Co., Ltd.'s "Harden Film N1102") and a 70 μm thick unstretched polypropylene film (Toyobo Co., Ltd.'s "P1146") as a heat-sealable resin layer were laminated on each laminate film by dry lamination using a polyurethane-based two-component curing adhesive (Mitsui Chemicals, Inc.'s "Takelac® A525S" and "Takenate® A50" blended in a 13.5:1 (mass ratio)). The laminated gas barrier laminate film for evaluation was obtained by aging at 40 °C for 4 days. The thickness of the adhesive layer formed with the urethane-based two-component curing adhesive after drying was approximately 4 μm. Samples were cut out at 500 mm intervals in the width direction and water vapor permeability measurements were performed.

[0063] (3) Retort processing method The laminated film or the laminate obtained in (2) above was subjected to a retort treatment at 130°C for 30 minutes using a hot water spray retort sterilizer ("RCS-60SPXTG" manufactured by Hisaka Seisakusho Co., Ltd.), followed by drying for 1 day in a 40°C room to obtain a laminate.

[0064] (4) Evaluation method for heat shrinkage before and after retort treatment A film measuring 210 mm in the transverse direction (TD) and 297 mm in the machine direction (MD) was cut from the roll, with the ends 50 mm inward from both ends. A test specimen measuring 210 mm in the transverse direction (TD) and 297 mm in the machine direction was also cut from the center of the roll. A 15 mm mark was made in the machine direction and a 10 mm mark was made in the machine direction at the center of the film. The spacing between the marks on the test specimens before retort treatment was measured to an accuracy of 0.1 mm. The test specimens were placed in a hot water spray retort sterilizer (Hisaka Works, Ltd., RCS-60SPXTG) and treated under moist heat conditions at 130°C for 30 minutes. After removing the test specimens from the retort sterilizer and cooling them to room temperature, the length and width were measured at the same locations as the initial measurements. The dimensional change of each test specimen was calculated as a percentage of the initial dimensional change in the machine direction and the machine direction. The dimensional change in each direction was calculated as the average of the measurements in that direction.

[0065] (5) Evaluation method for water vapor permeability The water vapor permeability of the laminated films obtained in (2) and (3) above was measured in accordance with JIS-K7129 using a water vapor permeability measuring device ("PERMATRAN-3 / 33MW" manufactured by MOCON) in an atmosphere at a temperature of 40°C and a relative humidity of 90%. The water vapor permeability was measured in the direction in which water vapor permeated from the substrate film side on which no protective layer was laminated to the protective layer side.

[0066] (6) Appearance evaluation method After the coating liquid was applied by the roll method, the appearance of the rolled up roll was visually inspected.

[0067] The materials used to form the protective layers in the examples and comparative examples were prepared as follows.

[0068] <Preparation of material used to form protective layer A (coating liquid a)> 30% of a polyester resin with a number-average molecular weight of 450 to 3,000 (a polyester primarily composed of a polycarboxylic acid component containing at least one ortho-oriented aromatic dicarboxylic acid or its anhydride, and a polyhydric alcohol component) was dissolved in 70% methyl ethyl ketone (polyester solution). A solution of a silane coupling agent ("KBM-603" manufactured by Shin-Etsu Chemical Co., Ltd.) in acetone and a trimethylolpropane adduct of meta-xylylene diisocyanate ("Takenate D-110N" manufactured by Mitsui Chemicals, Inc.: solids concentration 75%) were mixed and stirred for 10 minutes using a magnetic stirrer. The resulting mixture was diluted with methyl ethyl ketone, and the polyester solution was further added to obtain polyester urethane coating solution a with a solids concentration of 5%. <Preparation of material used to form protective layer B (coating liquid b)> 25% of a polyester resin (mainly composed of terephthalic acid, isophthalic acid, ethylene glycol, and propylene glycol) with a weight-average molecular weight of 35,000 was dissolved in 35% propyl acetate and 40% ethyl acetate (polyester solution). 14.00% of this solution was mixed with 41.40% ethyl acetate, 43.10% propyl acetate, 1.30% isocyanate-containing polyisocyanate (Coronate L, manufactured by Nippon Polyurethane Co., Ltd.), and 0.2% silane coupling agent (KBM-903, manufactured by Shin-Etsu Chemical Co., Ltd.) to obtain polyester urethane coating solution b with a solids concentration of 5%. <Preparation of material used to form protective layer C (coating liquid c)> Polymethacrylic acid having a weight-average molecular weight of 30,000 was diluted with an ethyl acetate / isopropyl alcohol mixed solvent (ethyl acetate / isopropyl alcohol=1:1 (mass ratio)) to obtain polymethacrylic acid coating solution c having a solid content concentration of 5%.

[0069] Example 1 The obtained coating solutions a to c were applied by roll coating onto the inorganic thin film layer of a 12 μm thick, 1,000 mm wide biaxially stretched polyester film, on which a 10 nm inorganic thin film layer of aluminum oxide had been formed. The thermal shrinkage in the MD and TD directions had been measured in advance. The temperature was raised and lowered at a heating rate of 20°C / sec or less so that the residence time in the oven was 10 seconds, and the film was dried until the film surface temperature reached the values ​​shown in Table 1, yielding a protective layer. The coating amount after drying was 0.3 g / m 2 The tension after passing through the dryer was set to 50 N / m by adjusting the rotation speed ratio of the rolls before and after the oven. In this way, a laminate film comprising a resin substrate, an inorganic thin film layer, and a protective layer was produced. The thermal shrinkage rates in the MD and TD directions of the obtained laminate film were measured, and a laminate was produced as described above. Furthermore, a retort treatment was performed at 130°C for 30 minutes, and the change in water vapor permeability was evaluated. The results are shown in Table 1.

[0070] Examples 2 to 4 A laminate was produced in the same manner as in Example 1, except that the surface temperatures of the protective layer and film and the tension after passing through the oven were changed as shown in Table 1, and the water vapor permeability was evaluated.

[0071] Example 5 Laminates were prepared in the same manner as in Example 1, except that biaxially stretched polyester films with inorganic vapor deposition layers formed thereon and having different widths were used, and the water vapor permeability was evaluated.

[0072] (Comparative Examples 1 and 2) A laminate was produced in the same manner as in Example 1, except that the film surface temperature and the tension after passing through the furnace were changed as shown in Table 1, and the water vapor permeability was evaluated.The value after retort treatment was found to have decreased.

[0073] (Comparative Example 3) When the film surface temperature was as shown in Table 1, the film after coating had strong wrinkles. A laminate was produced in the same manner as in Example 1, and the water vapor permeability was evaluated. The value was reduced even before retort treatment.

[0074] Comparative Example 4 When the film surface temperature was as shown in Table 1, the film surface after processing had tackiness and could not be evaluated.

[0075] (Comparative Example 5) When the tension after passing through the dryer was set as shown in Table 1, the tension value was too weak and the film could not be wound onto a roll.

[0076] (Comparative Example 6) A laminate was produced in the same manner as in Example 1 except that the protective layer was changed as shown in Table 1, and the water vapor permeability was evaluated. The value after retort treatment was found to have decreased.

[0077] (Comparative Example 7) A laminate was produced in the same manner as in Example 1, except that the biaxially oriented polyester film having an inorganic thin film layer of aluminum oxide formed thereon was subjected to only a drying process without applying a coating liquid, and the water vapor permeability was evaluated. The value was found to have decreased even before retort treatment.

[0078] [Table 1A]

[0079] [Table 1B] [Industrial Applicability]

[0080] The present invention provides a laminate film that exhibits excellent gas barrier properties not only under normal conditions but also after retort treatment. The gas barrier laminate film of the present invention has the advantages of being easy to manufacture, being economical and stable in production, and easily achieving uniform properties. Furthermore, because the improvement is made during the process, it is easy to handle high-mix, small-lot production. Therefore, the gas barrier laminate film can be widely used not only for food packaging for retort treatment, but also for packaging various foods, pharmaceuticals, industrial products, etc., as well as for industrial applications such as solar cells, electronic paper, organic EL devices, and semiconductor devices.

Claims

1. A laminated film having gas barrier properties, comprising a biaxially stretched polyethylene terephthalate resin film substrate, an inorganic thin film layer laminated on at least one side of the biaxially stretched polyethylene terephthalate resin film substrate, and a protective layer containing a urethane resin laminated on the inorganic thin film layer, wherein the laminated film satisfies the following requirements (1) to (3): (1) No layer is provided between the biaxially oriented polyethylene terephthalate resin film substrate and the inorganic thin film layer. (2) The thermal shrinkage rate in the MD direction before and after retort treatment at 130°C for 30 minutes is 1.2% or less. (3) A 15 μm biaxially oriented nylon film and a 70 μm unoriented polypropylene film were laminated on the surface of the protective layer of the laminated film by a dry lamination method using a polyurethane-based two-component curing adhesive applied to a thickness of 4 μm after drying, and the laminate was aged at a temperature of 40° C. for 4 days, and then subjected to a wet heat treatment at 130° C. for 30 minutes. The water vapor permeability after this was 2.0 g / m ２ ・It must be less than day.

2. 2. The laminated film according to claim 1, wherein the laminated film has a width of 1,000 mm or more and a difference Δ between the maximum MD shrinkage rate and the minimum MD shrinkage rate in the width direction when retorted at 130°C for 30 minutes is 0.4% or less.

3. 3. The laminated film according to claim 1, wherein the inorganic thin film layer contains at least one inorganic oxide containing silicon oxide and / or aluminum oxide.

4. 4. The laminated film according to claim 1, wherein the protective layer contains at least one type of polyester urethane resin.

5. 5. The laminated film according to claim 1, wherein the protective layer contains a silane coupling agent.

6. A laminate comprising the laminate film according to any one of claims 1 to 5 and a heat seal layer laminated on the surface of the protective layer.

7. A packaging bag comprising at least a portion thereof made of the laminate according to claim 6.

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