Gas barrier film

Abstract

To provide a gas barrier film which enhances adhesion between a base material composed of a polymer material having an antistatic function and a vapor-deposited film, can obtain high adhesiveness even after hot water treatment and causes no delamination.SOLUTION: There is provided a gas barrier film 1 which has an antistatic function and comprises: a vapor deposition film 20 in which a vapor deposition layer 30 and a coating layer 40 are laminated in this order on the processed surface layer of a base material 10 composed of propylene; and a sealant layer 60 composed of a heat-sealable thermoplastic resin, wherein the sealant layer is laminated on the coating layer of the vapor deposition film via an adhesive layer 50. The base material and the sealant layer are formed from a resin film, and the gas barrier film is formed without using any other resin film. The processed surface layer is a copolymer of propylene and ethylene or a copolymer of propylene and ethylene or 1-butene, and the adhesion strength between the base material and the vapor deposition layer after hot water treatment is 1.0 N / 15 mm or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a vapor-deposited film as a gas barrier material used in the packaging fields of foods, medicines, electronic products, etc., and a gas barrier film using the same. [Background technology]

[0002] Packaging materials used for packaging food, electronics, etc. are often required to have gas barrier properties that block oxygen, water vapor, and other gases that can cause deterioration of the contents, preventing them from permeating the packaging material and preserving their functions and properties. Vapor-deposited films, which use a vapor-deposited layer of metal foil such as aluminum, which is less affected by temperature and humidity, are known as packaging materials with gas barrier properties.

[0003] Another known configuration of vapor-deposited film is one in which a vapor-deposited film of inorganic oxide such as silicon oxide or aluminum oxide is formed on a substrate film made of a polymeric material by vacuum deposition or sputtering (see, for example, Patent Document 1). These gas barrier vapor-deposited films are transparent and have the ability to block gases such as oxygen and water vapor. Polyethylene terephthalate (PET) is often used as the substrate film. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Unexamined Patent Publication No. 60-49934 Summary of the Invention [Problem to be solved by the invention]

[0005] Packaging materials for powders, electronics, and other products require antistatic properties due to the characteristics of the contents. This antistatic property is necessary not only for the inner surface of the packaging material that comes into contact with the contents, but also for components that do not come into direct contact with the contents. For example, when packaging dried bonito flakes, the charge on the outer surface of the packaging material affects the filling of the contents. If an outer packaging material with low antistatic properties is used, the charge can attract the dried bonito flakes and cause them to become trapped in the packaging seal, resulting in poor sealing. For this reason, outer packaging materials that have both gas barrier properties and antistatic properties are desirable. However, when a vapor deposition layer is applied to an antistatic substrate using conventional methods, the action of the antistatic agent prevents sufficient adhesion between the substrate and the vapor deposition layer. This is thought to be due to the antistatic agent segregating to the outermost surface of the substrate, inhibiting adhesion with the vapor deposition layer.

[0006] To solve this problem, previous attempts have been made to improve the adhesion of metal or metal oxide depositions on plastic substrates by in-line pre-treatment using plasma.

[0007] The present invention is intended to solve the above-mentioned problems, and aims to provide a gas barrier film that strengthens the adhesion between a substrate made of a polymeric material having antistatic properties and a vapor-deposited film, and that maintains high adhesion even after hot water treatment and does not cause delamination. [Means for solving the problem]

[0008] The present invention provides a gas barrier film having an antistatic function, which comprises a vapor-deposited film having a vapor-deposited layer and a coating layer laminated in this order on the processed surface of a polypropylene substrate, and a sealant layer made of a heat-sealable thermoplastic resin. The sealant layer is laminated to the coating layer of the vapor-deposited film via an adhesive layer. The substrate and the sealant layer are formed of resin films, and the gas barrier film is formed without using any other resin films. The surface layer of the processed surface is a copolymer of propylene and ethylene or a copolymer containing propylene and ethylene or 1-butene, and the adhesive strength between the substrate and the vapor-deposited layer after hot water treatment is 1.0 N / 15 mm or more. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a gas barrier film that strengthens the adhesion between a substrate made of a polymeric material having antistatic properties and a vapor-deposited film, and that maintains high adhesion even after hot water treatment and does not cause delamination. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic cross-sectional view of a gas barrier film according to a simple embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment of the present invention will be described below with reference to FIG. 1 is a schematic cross-sectional view of a gas barrier film 1 according to this embodiment. The gas barrier film 1 comprises a vapor-deposited film 20, an adhesive layer 50, and a sealant layer 60. The vapor-deposited film 20 comprises a substrate 10, a pretreatment layer 10a, a vapor-deposited layer 30, and a coating layer 40.

[0012] The substrate 10 used in the present invention is made of a plastic material with antistatic properties, preferably a transparent film substrate to maximize the transparency of the vapor-deposited thin film layer. Examples of substrates include plastic materials containing at least one of polyethylene, polypropylene, polyamides, polyesters, polycarbonate, polyacrylonitrile, polystyrene, polyvinyl chloride, cellulose, triacetyl cellulose, polyvinyl alcohol, and polyurethanes, plastic materials containing at least one of these as copolymer components, and plastic materials containing at least one of these chemically modified forms. Examples of polyesters include polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and polybutylene naphthalate, either alone or as copolymers thereof. The substrate may be stretched or unstretched, and should preferably have mechanical strength and dimensional stability. The plastic material used in the present invention preferably has a surface layer made of propylene and ethylene, or a copolymer of propylene and ethylene or 1-butene. The substrate 10 may be a single layer of a copolymer of propylene and ethylene or a copolymer of propylene and ethylene or 1-butene, or may have a laminated structure in which at least one surface layer of the substrate 10 is a copolymer of propylene and ethylene or a copolymer of propylene and ethylene or 1-butene, and the other layers are homopolymers.

[0013] The substrate 10 used in the present invention is characterized by being a plastic material having an antistatic function, and has a surface resistivity of 1×10 11 It is desirable that it is [Ω / □] or higher. If the surface resistivity is lower than this value, sufficient adhesion between the substrate and the vapor-deposited layer cannot be obtained. To impart antistatic properties, an antistatic agent can be used on the surface layer of the substrate 10. Examples of antistatic agents include cationic surfactants, anionic surfactants, and nonionic surfactants.

[0014] The thickness of the substrate 10 is not particularly limited, and in consideration of its suitability as a packaging material, a film laminated with films of different properties can be used in addition to a single film. In consideration of the processability when forming a primer layer, a vapor-deposited thin film layer made of an inorganic oxide, and a gas barrier coating layer, a practical thickness is preferably in the range of 3 to 200 μm, and particularly preferably 6 to 30 μm.

[0015] Before forming the vapor deposition layer, a coating layer such as a thermoplastic resin, thermosetting resin, or ultraviolet-curable resin may be provided on the surface of the substrate as a pretreatment layer 10a to improve gas barrier properties and adhesion, or ion beam treatment, corona treatment, plasma treatment, ozone treatment, or flame treatment may be performed. The pretreatment layer and its formation method are not particularly limited. From the viewpoint of productivity, plasma treatment, which can be performed in-line, is preferred. Plasma treatment may be performed using a magnet to increase plasma density. The gas used in plasma treatment can be selected from one or more of oxygen, nitrogen, argon, and helium.

[0016] The vapor-deposited layer 30 is a layer whose main component is any of metallic aluminum, aluminum oxide, and silicon oxide, and exhibits gas barrier properties against predetermined gases such as oxygen, water vapor, etc. The vapor-deposited layer 30 may be either transparent or opaque.

[0017] The thickness of the vapor-deposited layer 30 varies depending on the type, composition, and film-forming method of the inorganic compound used, but can generally be set appropriately within the range of 3 to 300 nm. If the thickness of the vapor-deposited layer 30 is less than 3 nm, a uniform film may not be obtained or the film thickness may be insufficient, and the vapor-deposited layer may not fully function. If the thickness of the vapor-deposited layer 30 exceeds 300 nm, the vapor-deposited layer 30 becomes hard, and external factors such as bending or pulling after film formation may cause cracks in the vapor-deposited layer 30, resulting in a loss of gas barrier properties. The thickness of the vapor-deposited layer 30 is particularly preferably within the range of 6 to 150 nm.

[0018] There are no limitations on the method for forming the deposition layer 30, and for example, vacuum deposition, sputtering, ion plating, ion beam deposition, plasma vapor deposition (CVD), etc. Combining a plasma-assisted method, an ion beam-assisted method, etc., can form a dense deposition layer, improving gas barrier properties and adhesion.

[0019] The coating layer 40 further enhances the gas barrier properties of the vapor deposition layer 30. The coating layer 40 is formed using a coating agent whose main component is an aqueous solution or a water / alcohol mixed solution containing a water-soluble polymer and one or more metal alkoxides or their hydrolysates. For example, the coating agent is prepared by mixing a water-soluble polymer dissolved in an aqueous solvent (water or a water / alcohol mixed) with a metal alkoxide, either directly or after being hydrolyzed in advance. The coating layer 40 can be formed by applying this coating agent to the vapor deposition layer 30 and then drying it.

[0020] The components contained in the coating agent for forming the covering layer 40 will be described in more detail. Examples of water-soluble polymers used in the coating agent include polyvinyl alcohol (PVA), polyvinylpyrrolidone, starch, methyl cellulose, carboxymethyl cellulose, and sodium alginate. PVA is particularly preferred because it provides excellent gas barrier properties. PVA is generally obtained by saponifying polyvinyl acetate. As PVA, either so-called partially saponified PVA, in which several tens of percent of acetate groups remain, or complete PVA, in which only a few percent of acetate groups remain, can be used. PVA that is intermediate between the two may also be used.

[0021] The metal alkoxide used in the coating agent is a compound represented by the general formula M(OR)n (M: metals such as Si and Al, R: alkyl groups such as CH3 and C2H5). Specific examples include tetraethoxysilane [Si(OC2H5)4] and triisopropoxyaluminum Al[OCH(CH3)2]3. Examples of silane coupling agents include those having an epoxy group such as 3-glycidoxypropyltrimethoxysilane, those having an amino group such as 3-aminopropyltrimethoxysilane, those having a mercapto group such as 3-mercaptopropyltrimethoxysilane, those having an isocyanate group such as 3-isocyanatopropyltriethoxysilane, and tris-(3-trimethoxysilylpropyl)isocyanurate. The coating agent can be applied by any method known in the art, including commonly used methods such as dipping, roll coating, screen printing, spraying, and gravure printing.

[0022] The thickness of the coating layer 40 varies depending on the composition of the coating agent, the application conditions, etc., and is not particularly limited. However, if the thickness of the coating layer 40 after drying is less than 0.01 μm, the coating film may not be uniform and sufficient gas barrier properties may not be obtained. If the thickness after drying exceeds 50 μm, cracks may easily occur in the coating layer 40. Therefore, the preferred thickness of the coating layer 40 is, for example, in the range of 0.01 to 50 μm. The optimal thickness of the coating layer 40 is in the range of 0.1 to 10 μm.

[0023] The sealant layer 60 is a layer that is bonded by heat sealing when forming a bag-shaped package or the like using the gas barrier film 1. Examples of materials for the sealant layer 60 include resin materials such as polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene-methacrylic acid copolymer, ethylene-methacrylic acid ester copolymer, ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer, and metal cross-linked products thereof. The thickness of the sealant layer 60 is determined depending on the purpose, but is, for example, in the range of 15 to 200 μm.

[0024] The adhesive layer 50 bonds the sealant layer 60 and the coating layer 40. By using the adhesive layer 50, the resin film that will become the sealant layer 60 and the substrate 10 on which the vapor deposition layer 30 and the coating layer 40 have been formed can be bonded together by dry lamination. An example of a material for the adhesive layer 50 is a two-component curing polyurethane adhesive. A printed layer, an intervening film, a sealant layer, etc. can be laminated on the coating layer 40 to form a packaging material.

[0025] Next, a method for producing the vapor-deposited film 20 of this embodiment having the above-mentioned configuration will be described. First, a vapor-deposited layer 30 is formed on one surface of the substrate 10 (first step). Next, the above-mentioned coating agent is applied to the vapor-deposited layer 30 and dried to form a coating layer 40 on the vapor-deposited layer (second step), thereby producing the vapor-deposited film 20. Furthermore, an adhesive 50 is applied to the coating layer 40 of the vapor-deposited film 20, and a resin film that will become the sealant layer 60 is attached thereto (third step), thereby completing the gas barrier film 1. [Example]

[0026] The gas barrier film 1 of this embodiment will be further described using examples and comparative examples, but the present invention is not limited in any way by the specific contents of the examples and comparative examples.

[0027] Example 1 The substrate 10 is a film (thickness: 20 μm, surface resistance: 1.0×10) containing an antistatic agent and made by copolymerizing polypropylene and ethylene. 11 Ω / □) was used. Aluminum was evaporated in the vacuum chamber for the substrate 10, and a deposition layer 30 (thickness: 50 nm) made of metallic aluminum was formed by electron beam deposition.

[0028] A coating agent made by mixing the following (1) liquid and (2) liquid in a weight ratio of 6:4 was applied onto the vapor deposition layer 30 by gravure coating and dried to form a coating layer 40 with a thickness of 0.4 μm, thereby producing a vapor deposition film 20. (1) Liquid: 10.4 g of tetraethoxysilane was mixed with 89.6 g of hydrochloric acid (0.1 N) and stirred for 30 minutes to hydrolyze the solution, resulting in a solid content of 3 wt% (SiO2 equivalent). (2) Liquid: 3 wt% water / isopropyl alcohol solution of polyvinyl alcohol (water:isopropyl alcohol weight ratio 90:10).

[0029] Finally, an unstretched polypropylene film 60 (70 μm thick) was attached onto the coating layer 40 by dry lamination using a two-component curing polyurethane adhesive 50, thereby obtaining a gas barrier film 1 of Example 1.

[0030] Example 2 A gas barrier film 1 of Example 2 was produced in the same manner as in Example 1, except that the deposition material was Al and oxygen was introduced to form a deposition layer 30 made of aluminum oxide and having a thickness of 10 nm.

[0031] Example 3 A gas barrier film 1 of Example 3 was produced in the same manner as in Example 1, except that the deposition material was SiO and a deposition layer 30 made of silicon oxide and having a thickness of 30 nm was formed.

[0032] Example 4 Plasma treatment with Ar gas was performed on the substrate as pretreatment 10a (the surface resistance of the substrate was 2.0 × 10 12 A gas barrier film 1 of Example 4 was produced in the same manner as in Example 1, except that aluminum was continuously formed.

[0033] Example 5 Plasma treatment with Ar gas was performed on the substrate as pretreatment 10a (the surface resistance of the substrate was 2.0 × 10 12 A gas barrier film 1 of Example 5 was produced in the same manner as in Example 2, except that aluminum oxide was continuously formed.

[0034] Example 6 Plasma treatment with Ar gas was performed on the substrate as pretreatment 10a (the surface resistance of the substrate was 2.0 × 1012 A gas barrier film 1 of Example 6 was produced in the same manner as in Example 3, except that silicon oxide was continuously formed.

[0035] Example 7 A gas barrier film 1 of Example 7 was produced in the same manner as in Example 1, except that a urethane resin layer 50 was formed on the substrate as a pretreatment 10a.

[0036] Example 8 A gas barrier film 1 of Example 8 was produced in the same manner as in Example 2, except that a urethane resin layer 50 was formed on the substrate as a pretreatment 10a.

[0037] Example 9 A gas barrier film 1 of Example 9 was produced in the same manner as in Example 3, except that a urethane resin layer 50 was formed on the substrate as a pretreatment 10a.

[0038] Example 10 Surface resistance is 1.0 x 10 12 A gas barrier film 1 of Example 10 was produced in the same manner as in Example 3, except that a substrate 10 of Ω / □ was used.

[0039] Example 11 Surface resistance is 1.0 x 10 13 A gas barrier film 1 of Example 11 was produced in the same manner as in Example 3, except that a substrate 10 of Ω / □ was used.

[0040] (Comparative Example 1) Surface resistance is 1.0 x 10 9 A gas barrier film 1 of Comparative Example 1 was produced in the same manner as in Example 3, except that a substrate 10 having an Ω / □ point was used.

[0041] The substrate 10 of Comparative Example 1 was subjected to a plasma treatment with Ar gas as a pretreatment 10a (the surface resistance of the substrate was 2.0 × 10 10 Gas barrier film 1 of Comparative Example 2 was produced in the same manner as in Example 3, except that silicon oxide was continuously formed.

[0042] (Comparative Example 3) A gas barrier film 1 of Comparative Example 3 was produced in the same manner as in Example 3, except that a urethane resin layer 50 was formed on the substrate of Comparative Example 1 as a pretreatment 10a.

[0043] <Evaluation 1: Adhesion evaluation after hot water treatment> Two gas barrier films 1 of each example were stacked with the sealant layers 60 facing each other, and three sides were joined by heat sealing to produce a pouch (packaging container) of each example. Each pouch was filled with water as the content, and the open side was sealed by heat sealing. Then, a boiling treatment (90°C for 30 minutes) was performed as a hot water treatment. After the hot water treatment, a test piece was cut out from the part of each pouch that had been in contact with the content in accordance with JIS K6854-2, and measured using an Orientec Tensilon universal testing machine RTC-1250.

[0044] <Evaluation 2: Gas barrier property evaluation after hot water treatment> After the pouches of each example prepared by the above procedure were prepared and subjected to hot water treatment, the pouches were opened and the oxygen permeability (unit: cc / m) of the gas barrier film 1 was measured. 2 ·day·atm, measurement conditions: 30℃-70%RH), and water vapor permeability (unit: g / m 2 The results are shown in Table 1.

[0045] [Table 1]

[0046] From Examples 4 to 6, the pretreatment plasma treatment increased adhesion and maintained gas barrier properties. From Examples 7 to 9, the pretreatment thermosetting resin layer increased adhesion and also improved oxygen barrier properties. From Examples 1 to 11, the surface resistivity of the substrate surface was 1.0×10 11 When the antistatic function is [Ω / □] or more, high adhesion is obtained, and as can be seen from Comparative Examples 1 to 3, the surface resistance value is 1.0 × 10 11If the resistance is lower than [Ω / □], the adhesion is significantly reduced and delamination becomes more likely to occur. [Explanation of symbols]

[0047] 1...Gas barrier film 10...Base material 10a...Pretreatment layer 20...Vapor-deposited film 30...Vapour-deposited layer 40…Covering layer 50...Adhesive layer 60...Sealant layer

Claims

1. A gas barrier film having an antistatic function, the gas barrier film comprising a vapor-deposited film having a vapor-deposited layer and a coating layer laminated in this order on the processed surface of a polypropylene substrate, and a sealant layer made of a heat-sealable thermoplastic resin, the sealant layer is laminated on the coating layer of the vapor-deposited film via an adhesive layer; the substrate and the sealant layer are formed of resin films, and the gas barrier film is formed without using any other resin film; the surface layer to be machined is a copolymer of propylene and ethylene, or a copolymer containing propylene and ethylene or 1-butene, The adhesion strength between the substrate and the vapor deposition layer after the hot water treatment is 1.0 N / 15 mm or more. Gas barrier film.

2. The surface layer of the processed surface is provided with any one of a thermoplastic resin layer, a thermosetting resin layer, and an ultraviolet curing resin layer, or a surface treatment layer obtained by plasma treatment. The gas barrier film according to claim 1 .

3. The vapor-deposited layer is composed mainly of aluminum, aluminum oxide, or silicon oxide. The gas barrier film according to claim 1 or 2.

4. a composite coating film having at least one component selected from a hydroxyl group-containing polymer compound, a metal alkoxide and / or its hydrolysate and / or its polymer on the vapor deposition layer; The gas barrier film according to any one of claims 1 to 3.

5. After hot water treatment at a temperature of 90°C or higher for 30 minutes or more, the oxygen permeability at 30°C and 70% RH is 3 cc / m ２ ・day・atm or less, 40℃90%RH water vapor transmission rate is 1g / m ２ ・day or less, The gas barrier film according to any one of claims 1 to 4.

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