Gas Barrier Film

Abstract

To provide a gas barrier film having an excellent gas barrier performance as a packaging material even without using an adhesive agent having an oxygen barrier performance.SOLUTION: A gas barrier film 1 includes: a substrate 10 having polyethylene as a primary constituent; and a gas barrier layer 30 laminated on a first face 10a being one side of the substrate 10. The substrate 10 includes: a first resin layer 11 constituting the first face 10a and having polyethylene as a primary constituent; and a second resin layer 12 arranged on a side closer than the first resin layer 11 to a second face 10b being the other face of the substrate 10, and having an ethylene-vinyl alcohol copolymer as a primary constituent. The substrate 10 has a crystallinity index of less than 35% measured within a range of a diffraction angle 10° to 30° by a 2θ / θ scanning measurement using a parallel beam method of an X-ray diffraction method and calculated by a ratio of crystal peak areas of PE(110) and PE(200) to a whole peak area.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a gas barrier film. The gas barrier film of the present invention is suitable for packaging foods, medicines, precision electronic parts, etc. [Background technology]

[0002] Packaging materials used for packaging foods, pharmaceuticals, etc. are required to have gas barrier properties that block oxygen, water vapor, and other gases that may cause deterioration of the contents, which permeate the packaging material, in order to prevent deterioration of the contents and maintain their functions and properties.Gas barrier films that use metal foil, such as aluminum, as a gas barrier layer, which is less affected by temperature, humidity, etc., are known as packaging materials with gas barrier properties.

[0003] Another known gas barrier film configuration is a film in which an inorganic oxide film such as silicon oxide or aluminum oxide is formed on a base layer film made of a polymer material by vacuum deposition, sputtering, or the like. These gas barrier films are transparent and have the ability to block gases such as oxygen and water vapor. Polyethylene terephthalate (PET) is often used as the base layer film.

[0004] In recent years, growing environmental awareness stemming from the problem of marine plastic waste has led to calls for even more efficient sorting, collection, and recycling of plastic waste, resulting in a growing demand for gas barrier films that use base layer films made from polypropylene (PP) or polyethylene (PE).

[0005] Patent Document 1 below proposes a barrier film (laminate) that uses polyethylene and has excellent recyclability. Patent Document 2 proposes a film in which an adhesive layer between a base layer and a barrier layer is made of a material that has oxygen barrier properties. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2020-055157 [Patent Document 2] Japanese Patent Application Publication No. 2018-016012 Summary of the Invention [Problem to be solved by the invention]

[0007] However, there is a possibility that the gas barrier performance may be insufficient in a gas barrier film in which a vapor-deposited film is simply formed as a barrier layer on a polyethylene substrate film, as in Patent Document 1. Patent Document 2 has the problem that the oxygen barrier property cannot be improved unless an adhesive having oxygen barrier property is used.

[0008] The present invention has been made in view of the above-mentioned problems, and provides a gas barrier film that has excellent gas barrier properties as a packaging material without using an adhesive having oxygen barrier properties. [Means for solving the problem]

[0009] In order to achieve the above object, the present invention employs the following means. That is, the gas barrier film according to the present invention is a gas barrier film comprising a substrate primarily composed of polyethylene and a gas barrier layer laminated on a first surface, which is one surface of the substrate, wherein the substrate has a first resin layer primarily composed of polyethylene constituting the first surface, and a second resin layer primarily composed of an ethylene-vinyl alcohol copolymer, which is disposed closer to the second surface, which is the other surface of the substrate, than the first resin layer; and the substrate has a crystallinity of less than 35%, as calculated from the ratio of the crystalline peak areas of PE(110) and PE(200) to the total peak area, measured by 2θ / θ scan measurement using the parallel beam method of X-ray diffraction over a diffraction angle range of 10° to 30°. [Effects of the Invention]

[0010] The gas barrier film according to the present invention provides a gas barrier film that has excellent gas barrier properties as a packaging material even without using an adhesive having oxygen barrier properties. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view schematically illustrating a gas barrier film according to one embodiment of the present invention. [Figure 2] FIG. 1 is a cross-sectional view schematically showing a gas barrier film according to Modification 1 of the present invention. [Figure 3] FIG. 10 is a cross-sectional view schematically showing a gas barrier film according to Modification 2 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] A gas barrier film according to one embodiment of the present invention will be described. 1 is a cross-sectional view schematically illustrating a gas barrier film according to one embodiment of the present invention, the gas barrier film 1 includes a substrate 10 and a gas barrier layer 30.

[0013] The substrate 10 is a film containing a resin whose main component is polyethylene. One surface of the substrate 10 is referred to as a first surface 10a, and the other surface of the substrate 10 is referred to as a second surface 10b. The gas barrier layer 30 is laminated on the first surface 10a of the substrate 10.

[0014] The substrate 10 has a first resin layer 11 and a second resin layer 12. The first resin layer 11 constitutes a first surface 10a. The second resin layer 12 is disposed closer to the second surface 10b than the first resin layer 11. In this embodiment, the second resin layer 12 is disposed adjacent to the first resin layer 11 and constitutes the second surface 10b.

[0015] The first resin layer 11 is a resin layer mainly containing polyethylene. For example, the first resin layer 11 typically contains only polyethylene as a resin component. The thickness of the first resin layer 11 is preferably in the range of 2.4 to 160 μm.

[0016] The second resin layer 12 is a resin layer mainly made of ethylene-vinyl alcohol copolymer. For example, the second resin layer 12 typically contains only ethylene-vinyl alcohol copolymer as a resin component. The thickness of the second resin layer 12 is preferably in the range of 0.6 to 40 μm.

[0017] The type of polyethylene constituting the first resin layer 11 is not particularly limited, but is preferably any one of high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, and very low-density polyethylene.

[0018] In the substrate 10, at least one first resin layer 11 may be provided on the first surface 10a side, and the first resin layer 11 may be provided on both sides of the second resin layer 12. In this case, the polyethylene density may be different between one first resin layer 11 and the other first resin layer 11 sandwiching the second resin layer 12. Also, a different resin layer may be provided between the first resin layer 11 and the second resin layer 12. The first resin layer 11 and the second resin layer 12 are bonded together without using an adhesive, and may be bonded by extrusion lamination using a fluid resin, inflation method, or the like.

[0019] There is no particular limitation on the thickness of the substrate 10. Considering the processability when forming the gas barrier layer 30, the coating layer 60 described below, etc., the thickness of the substrate 10 is preferably in the range of 3 to 200 μm, and more preferably 6 to 90 μm, for practical purposes. There is also no particular limitation on the thickness of each layer constituting the substrate 10, and there is no particular limitation on the thickness ratio of each layer, but in consideration of recyclability, it is preferable that the thickness of the first resin layer 11, which is mainly made of polyethylene, accounts for 80% or more of the total thickness of the substrate 10.

[0020] The substrate 10 may contain additives that are not resin components. The additives can be appropriately selected from various known additives. Examples of additives include antiblocking agents (AB agents), heat stabilizers, weather stabilizers, UV absorbers, lubricants, slip agents, nucleating agents, antistatic agents, antifogging agents, pigments, and dyes. The AB agent may be either organic or inorganic, but is preferably not added to the first surface 10a of the substrate 10 because it may adversely affect the formation of the gas barrier layer. These additives may be used alone or in combination of two or more. Of the above, lubricants and slip agents are preferred from the viewpoint of processability. The content of the additives in the substrate 10 can be appropriately adjusted within a range that does not impair the effects of this embodiment.

[0021] The substrate 10 may be an unstretched film, or may be a stretched film such as a uniaxially stretched or biaxially stretched film.

[0022] The substrate 10 preferably has a crystallinity of less than 35%, as calculated by measuring the first surface 10a of the substrate 10 by 2θ / θ scan measurement using the parallel beam method of X-ray diffraction (XRD) at a diffraction angle range of 10° to 30° and calculating the ratio of the crystalline peak area of ​​polyethylene (110) and polyethylene (200) to the total peak area. By making the crystallinity of the substrate 10 less than 35%, good adhesion can be obtained when multiple resin films are laminated.

[0023] An example of a method for measuring the crystallinity will be described below.

[0024] The crystallinity of a resin film can be measured by 2θ / θ scanning in out-of-plane measurement of the X-ray diffraction method, thereby obtaining an X-ray diffraction pattern. When measuring resin films, it is preferable to use characteristic X-rays, CuKα, collimate the X-rays using a multilayer mirror and allow the X-rays to enter the resin film, and use a scintillation detector equipped with a flat collimator as the light-receiving unit (parallel beam method). Another known X-ray diffraction method besides the parallel beam method is the focusing method, but with the focusing method, measurement results can be easily affected by peak broadening due to misalignment of the measurement surface when using samples with uneven surfaces, such as resin films.In contrast, with the parallel beam method, misalignment of the measurement surface has little effect on measurement results, even when using samples with uneven surfaces. When the resin film is a polyethylene film, it is preferable to scan at a diffraction angle range of 10° to 30°. When scanning in this range, two sharp crystalline peaks corresponding to the PE(110) and PE(200) planes and a broad amorphous peak (halo peak) are observed. These three peaks are separated and analyzed, and the areas of the crystalline and amorphous peaks are calculated, and the degree of crystallinity can be calculated using equation (1). Crystallinity = crystalline peak area / (crystalline peak area + amorphous peak area) (1) Since the surface of the resin film is not flat and there is a possibility that deviations may occur in the measurement surface, it is preferable to use the parallel beam method.

[0025] The crystallinity shows a certain correlation with the degree of orientation of the resin film, and tends to be smaller for unstretched films, but the crystallinity of a very small number of stretched films may also be within the above numerical range. In other words, the crystallinity is a parameter independent of the general distinction between stretched and unstretched resin films.

[0026] The gas barrier layer 30 is laminated on the first surface 10a of the substrate 10. As long as the gas barrier layer 30 is laminated on the first surface 10a of the substrate 10, another layer may be interposed between the gas barrier layer 30 and the substrate 10.

[0027] The gas barrier layer 30 is an inorganic oxide layer. The gas barrier layer 30 is a layer containing any of silicon oxide, silicon oxide containing carbon, silicon nitride, metallic aluminum, and aluminum oxide. The gas barrier layer 30 is a layer that exhibits barrier properties against predetermined gases such as oxygen and water vapor. The gas barrier layer 30 may be transparent or opaque.

[0028] The thickness of the gas barrier layer 30 varies depending on the type and composition of the components used and the film-forming method, but can generally be set appropriately within the range of 3 to 300 nm. If the thickness of the gas barrier layer 30 is less than 3 nm, a uniform film may not be obtained or the film thickness may be insufficient, and the gas barrier layer may not fully function. If the thickness of the gas barrier layer 30 exceeds 300 nm, external factors such as bending or pulling after film formation may cause cracks in the gas barrier layer 30, resulting in a loss of barrier properties. The thickness of the gas barrier layer 30 is more preferably within the range of 6 to 150 nm.

[0029] There are no limitations on the method for forming the gas barrier layer 30, and examples of methods that can be used include vacuum deposition, plasma activated deposition, ion beam deposition, ion plating, sputtering, plasma enhanced chemical vapor deposition (PECVD), etc. Combining a plasma assisted method, an ion beam assisted method, etc., can form a dense gas barrier layer 30, improving the barrier properties.

[0030] In the gas barrier film 1 of this embodiment, the substrate 10 has a first resin layer 11 that constitutes the first surface 10a and is primarily made of polyethylene, and a second resin layer that is disposed closer to the second surface 10b of the substrate 10 than the first resin layer 11 and is primarily made of an ethylene-vinyl alcohol copolymer. The substrate 10 has a crystallinity of less than 35%, as calculated by the ratio of the PE(110) and PE(200) crystal peak areas to the total peak area when measured using a parallel beam X-ray diffraction method at diffraction angles ranging from 10° to 30°. Therefore, the substrate 10 has excellent gas barrier properties as a packaging material, even without the use of an adhesive with oxygen barrier properties.

[0031] The configuration of the gas barrier film of this embodiment is not limited to the above-described configuration.

[0032] (Variation 1) As shown in FIG. 2, the gas barrier film 1A of Modification 1 includes a pretreatment layer 20 provided between the substrate 10 and the gas barrier layer 30. The pretreatment layer 20 may be provided before the gas barrier layer 30 is formed on the first surface 10a of the substrate 10. By providing the pretreatment layer 20, the film-forming properties and adhesive strength of the gas barrier layer 30 can be improved. There are no limitations on the components of the pretreatment layer 20 or the method for forming it, and it can be selected from thermoplastic resins, thermosetting resins, ultraviolet-curable resins, plasma treatment, or the like.

[0033] When a resin layer is used for the pretreatment layer 20, the content of the organic polymer in the pretreatment layer 20 may be, for example, 70% by mass or more, or 80% by mass or more. Examples of organic polymers include polyacrylic resins, polyester resins, polycarbonate resins, polyurethane resins, polyamide resins, polyolefin resins, polyimide resins, melamine resins, and phenolic resins. In consideration of the adhesive strength between the pretreatment layer 20 and the gas barrier layer 30, the organic polymer preferably includes at least one of a polyacrylic resin, a polyol resin, a polyurethane resin, a polyamide resin, or a reaction product of these organic polymers. The pretreatment layer 20 may also include a silane coupling agent, an organic titanate, or a modified silicone oil.

[0034] More preferred organic polymers used in the pretreatment layer 20 include organic polymers having urethane bonds formed by the reaction of polyols having two or more hydroxyl groups at the polymer terminal with an isocyanate compound, and / or organic polymers containing a reaction product of polyols having two or more hydroxyl groups at the polymer terminal with an organic silane compound such as a silane coupling agent or its hydrolyzate.

[0035] Examples of polyols include at least one selected from acrylic polyol, polyvinyl acetal, polystyrene polyol, and polyurethane polyol. The acrylic polyol may be obtained by polymerizing an acrylic acid derivative monomer, or may be obtained by copolymerizing an acrylic acid derivative monomer with another monomer. Examples of the acrylic acid derivative monomer include ethyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, and hydroxybutyl methacrylate. Examples of the monomer copolymerized with the acrylic acid derivative monomer include styrene.

[0036] The isocyanate compound reacts with the polyol to form a urethane bond, thereby enhancing the adhesion between the pretreatment layer 20 and the gas barrier layer 30. In other words, the isocyanate compound functions as a crosslinking agent or curing agent. Examples of isocyanate compounds include aromatic monomers such as tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), aliphatic monomers such as xylene diisocyanate (XDI), hexamethylene diisocyanate (HMDI), and isophorone diisocyanate (IPDI), as well as polymers and derivatives thereof. The above-mentioned isocyanate compounds may be used singly or in combination of two or more.

[0037] Examples of silane coupling agents include vinyltrimethoxysilane, γ-chloropropylmethyldimethoxysilane, γ-chloropropyltrimethoxysilane, glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and γ-methacryloxypropylmethyldimethoxysilane. The organic silane compound may be a hydrolyzate of these silane coupling agents. The organic silane compound may contain one of the above-mentioned silane coupling agents and their hydrolyzates, or two or more of them in combination.

[0038] The resin layer provided as the pretreatment layer 20 can be formed by preparing a mixed solution by blending the above-mentioned components in an organic solvent in any ratio, and using the prepared mixed solution on the first surface 10a of the substrate 10. The mixed solution may contain, for example, a curing accelerator such as a tertiary amine, an imidazole derivative, a metal salt compound of a carboxylic acid, a quaternary ammonium salt, or a quaternary phosphonium salt; an antioxidant such as a phenol-based, sulfur-based, or phosphite-based antioxidant; a leveling agent; a flow adjuster; a catalyst; a crosslinking reaction accelerator; a filler; etc.

[0039] The mixed liquid can be coated onto the first surface 10a of the substrate 10 using a known printing method such as offset printing, gravure printing, or silk screen printing, or a known application method such as roll coating, knife edge coating, or gravure coating. After coating, the pretreatment layer 20 can be formed by heating to, for example, 50 to 200°C and drying and / or curing.

[0040] When a resin layer is formed as the pretreatment layer 20, its thickness may be adjusted depending on the application or desired properties, but is preferably 0.01 to 1 μm, and more preferably 0.01 to 0.5 μm. If the thickness of the pretreatment layer 20 is 0.01 μm or more, sufficient adhesion strength between the pretreatment layer 20 and the gas barrier layer 30 is obtained, and the gas barrier properties are also good. If the thickness of the pretreatment layer 20 is 1 μm or less, it is easy to form a uniform coated surface, and drying load and production costs can be reduced.

[0041] When forming the pretreatment layer 20 by plasma treatment, plasma treatment that can be performed in-line is preferable from the viewpoint of productivity. The plasma treatment method is not particularly limited to glow discharge, and a magnet may be used to increase the plasma density. The gas used in the plasma treatment can be selected from one or more of oxygen, nitrogen, and argon.

[0042] (Variation 2) 3, the gas barrier film 1B of the second modification includes a coating layer provided on the surface of the gas barrier layer 30 facing away from the substrate 10. The coating layer 60 protects the gas barrier layer 30 and further enhances the barrier properties of the gas barrier film 1.

[0043] The coating layer 60 can be made of a thermoplastic resin, a thermosetting resin, an ultraviolet-curable resin, a metal alkoxide, a water-soluble polymer, a polycarboxylic acid polymer, a polyvalent metal compound, or a polyvalent metal salt of a carboxylic acid, which is a reaction product of a polycarboxylic acid polymer and a polyvalent metal compound. Metal alkoxides and water-soluble polymers, which have excellent oxygen barrier properties, are particularly preferred. This coating layer 60 is formed using a coating agent whose main component is an aqueous solution or water / alcohol mixture containing a water-soluble polymer and one or more metal alkoxides or their hydrolyzates. For example, the coating agent is prepared by mixing a water-soluble polymer dissolved in an aqueous solvent (water or a water / alcohol mixture) with a metal alkoxide, either directly or after pre-hydrolysis. The coating layer 60 can be formed by applying this coating agent to the gas barrier layer 30 and then drying it.

[0044] Examples of coating methods for the coating layer 60 include casting, dipping, roll coating, gravure coating, screen printing, reverse coating, spray coating, kit coating, die coating, metalling bar coating, chamber doctor combined coating, curtain coating, etc.

[0045] The thickness of the coating layer 60 varies depending on the composition of the coating agent used, the application conditions, etc., and is not particularly limited. However, if the thickness of the coating layer 60 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 are likely to occur in the coating layer 60. Therefore, a suitable thickness of the coating layer 60 is, for example, in the range of 0.01 to 50 μm, and an optimal thickness of the coating layer 60 is, for example, in the range of 0.1 to 10 μm.

[0046] The gas barrier film 1 of the present embodiment having the above-described configuration exhibits high gas barrier properties, and since the main resin component is polyethylene, it is easy to make the ratio of the main resin component in the gas barrier film 1 90 mass % or more. In other words, the gas barrier film 1 can be configured as a highly recyclable mono-material.

[0047] When producing a packaging material such as a packaging bag using the gas barrier film 1, if a heat-sealable heat seal layer 50 is further provided on the gas barrier layer 30, the packaging material can be easily produced by heat-sealing the heat seal layers together. In this case, too, the packaging material can be made into a mono-material by using polyethylene as the main resin component of the heat seal layer 50. When a coating layer 60 is provided, the heat seal layer 50 can be provided on the surface of the coating layer 60 facing away from the substrate 10. Note that other layers may be provided as appropriate between the heat seal layer 50 and the gas barrier layer 30 or the coating layer 60.

[0048] The heat seal layer 50 can be recycled by using the same polyethylene as the first resin layer 11 of the substrate 10 as its material. Low-density polyethylene or linear low-density polyethylene is preferably used as the polyethylene resin used for the heat seal layer 50 because it is easily heat-sealable. The thickness of the heat seal layer 50 is determined depending on the purpose, but can be, for example, about 50 to 200 μm. The heat seal layer 50 is laminated on the gas barrier layer 30 or the coating layer 60 via an adhesive layer 40 made of an adhesive.

[0049] A known dry lamination adhesive can be used for the adhesive layer 40. There are no particular limitations on the dry lamination adhesive, but specific examples include two-component curing ester adhesives, ether adhesives, and urethane adhesives. The heat seal layer 50 may also be laminated by extrusion lamination using a fluid resin.

[0050] A gas barrier adhesive may be used for the adhesive layer 40. By applying a gas barrier adhesive to the adhesive layer 40, the gas barrier properties can be further improved. The oxygen permeability of the gas barrier adhesive is 150 cc / m 2 ·day·atm or less is preferable, and 100cc / m 2 ·day·atm or less is more preferable, and 80cc / m 2 ·day·atm or less is more preferable, and 50cc / m 2 It is particularly preferable that the oxygen permeability is 1000 kJ / cm 3 / day 1000 kJ / cm 3 or less. By having the oxygen permeability within the above range, the gas barrier properties of the gas barrier film can be sufficiently improved, and even if minor cracks occur in the gas barrier layer 30, the gas barrier adhesive can fill in the gaps and fill in the cracks, thereby preventing a decrease in the gas barrier properties.

[0051] The gas barrier adhesive may be any adhesive that exhibits gas barrier properties after curing, such as epoxy adhesives, polyester-polyurethane adhesives, etc. Specific examples include "Maxieve" manufactured by Mitsubishi Gas Chemical Company, Inc. and "Paslim" manufactured by DIC Corporation.

[0052] The thickness of the adhesive layer 40 is preferably 0.1 to 20 μm, more preferably 0.5 to 10 μm, and even more preferably 1 to 5 μm. When the thickness of the adhesive layer 40 is equal to or greater than the above-mentioned lower limit, cushioning properties that absorb external impacts can be obtained, and cracking of the gas barrier layer 30 due to impacts can be prevented. On the other hand, when the thickness of the adhesive layer 40 is equal to or less than the above-mentioned upper limit, the flexibility of the gas barrier laminate tends to be sufficiently maintained.

[0053] In addition to the above conditions, it is particularly preferable that the thickness of the adhesive layer 40 is at least 50 times the thickness of the gas barrier layer 30. When the thickness of the adhesive layer 40 satisfies the above conditions, cracking of the gas barrier layer 30 can be more sufficiently suppressed, and when a gas barrier adhesive is used for the adhesive layer 40, the gas barrier properties of the gas barrier film 1 can be further improved. Furthermore, when the thickness of the adhesive layer 40 satisfies the above conditions, it is possible to further enhance the cushioning properties that absorb external impacts, and to prevent the gas barrier layer 30 from cracking due to impact. On the other hand, from the viewpoints of maintaining the flexibility of the gas barrier film 1, processability, and cost, it is preferable that the thickness of the adhesive layer 40 be no more than 300 times the thickness of the gas barrier layer 30.

[0054] The adhesive for forming the adhesive layer 40 can be applied by, for example, bar coating, dipping, roll coating, gravure coating, reverse coating, air knife coating, comma coating, die coating, screen printing, spray coating, gravure offset, or the like. The temperature at which the coating film formed by applying the adhesive is dried can be, for example, 30 to 200°C, and preferably 50 to 180°C. The temperature at which the coating film is cured can be, for example, room temperature (27°C) to 70°C, and preferably 30 to 60°C. By keeping the drying and curing temperatures within the above ranges, the occurrence of cracks in the gas barrier layer 30 and the adhesive layer 40 can be further suppressed, and excellent gas barrier properties can be achieved.

[0055] It is more preferable that the adhesive layer 40 and the gas barrier layer 30 are in direct contact with each other from the viewpoint of preventing cracking of the gas barrier layer 30. Therefore, the adhesive is preferably formed by applying the adhesive onto the gas barrier layer 30, and then drying and curing the adhesive.

[0056] A printing layer can be provided on the substrate 10 or the heat seal layer 50. Generally, the printing layer is provided in a position visible from the outside of the gas barrier film for the purpose of displaying information about the contents, identifying the contents, or improving the design of the packaging bag. The printing method and printing ink are not particularly limited, and are appropriately selected from known printing methods and printing inks taking into consideration printability on the film, design characteristics such as color tone, adhesion, safety as a food container, and the like. Examples of printing methods that can be used include gravure printing, offset printing, gravure-offset printing, flexographic printing, and inkjet printing. Among these, gravure printing is preferred from the standpoints of productivity and high-resolution images. The printing layer may or may not be provided as appropriate depending on the intended use.

[0057] In order to improve the adhesion of the printing layer, the surface of the layer on which the printing layer is formed may be subjected to various pretreatments such as corona treatment, plasma treatment, and flame treatment, or a coating layer such as an easy-adhesion layer may be provided.

[0058] A printed substrate may be bonded as the second substrate 70 to the second surface 10b of the substrate 10, which is the surface opposite to the first surface 10a. The second substrate 70 can be made of the same polyethylene as the first resin layer 11 of the substrate 10, making it recyclable. The second surface 10b of the substrate may be subjected to various pretreatments, such as corona treatment, plasma treatment, or flame treatment, or may be provided with a coating layer, such as an easy-adhesion layer, to enhance adhesion to the second substrate 70. Dry lamination or extrusion lamination using a known dry lamination adhesive can be used. Specifically, the substrate 10 and the second substrate 70 can be bonded via the adhesive layer 40 described above.

[0059] The oxygen permeability of Gas Barrier Film 1 is 3.0 cc / (m 2 ·day·atm) or less, and the water vapor permeability is 3.0g / (m 2 ·day) or less.

[0060] The gas barrier film of this embodiment will be further described using examples and comparative examples, but the present invention is not limited to the specific contents of the examples and comparative examples.

[0061] Example 1 The substrate 10 used was a film (thickness: 30 μm) with a crystallinity of 12.5%, in which a resin layer mainly made of ethylene-vinyl alcohol copolymer (EVOH) was laminated on both sides with a resin layer mainly made of polyethylene. SiO was sublimated in a vacuum chamber, and a gas barrier layer 30 (thickness: 30 nm) made of silicon oxide (SiOx) was formed on the first surface 10a of the substrate 10 by electron beam evaporation, thereby producing a gas barrier film 1 of Example 1.

[0062] Example 2 A two-component curing polyurethane adhesive was applied to the gas barrier layer 30 by gravure coating and dried to form an adhesive layer 40. A heat seal layer 50 made of a polyethylene film (thickness: 60 μm) with a crystallinity of 16.5% was attached via the adhesive layer 40. A gas barrier film 1 of Example 2 was produced in the same manner as in Example 1 except for the above.

[0063] Example 3 A thermosetting resin layer was provided as a pretreatment layer 20 on the first surface 10a of the substrate 10. The thermosetting resin layer was prepared by mixing acrylic polyol and tolylene diisocyanate so that the number of NCO groups in the tolylene diisocyanate was equal to the number of OH groups in the acrylic polyol, and then diluting the mixture with ethyl acetate to a total solids content (total amount of acrylic polyol and tolylene diisocyanate) of 5% by mass. To the diluted mixture, β-(3,4-epoxycyclohexyl)trimethoxysilane was added in an amount of 5 parts by mass per 100 parts by mass of the total amount of acrylic polyol and tolylene diisocyanate, and the mixture was mixed. The thermosetting resin was applied to the first surface 10a by gravure coating, dried, and cured to form a thermosetting resin layer. In addition, a gas barrier layer 30 (film thickness: 10 nm) made of silicon oxide (SiOx) was formed on the pretreatment layer 20. Otherwise, a gas barrier film 1 of Example 3 was produced in the same manner as in Example 2.

[0064] Example 4 The substrate 10 used was a film (thickness 30 μm) with a crystallinity of 14.2%, in which a resin layer mainly made of ethylene-vinyl alcohol copolymer (EVOH) was laminated on one side with a resin layer mainly made of polyethylene. The first surface 10a of the substrate 10, on which a resin layer mainly made of polyethylene is laminated, is treated with plasma using Ar gas at 100 W·sec / m as a pretreatment layer 20. 2 The treatment was carried out at a treatment intensity of 1000 nm. In addition, a gas barrier layer 30 (film thickness: 40 nm) made of silicon oxide (SiOx) was formed on the pretreatment layer 20. Otherwise, a gas barrier film 1 of Example 4 was produced in the same manner as in Example 3. The treatment intensity of the plasma treatment was calculated as follows. Power density [W / m 2 ] = input power [W] / cathode area [m 2 ] Processing time [sec] = electrode MD width [m] / processing speed [m / sec] Treatment intensity = power density [W / m 2 ]·Processing time [sec]

[0065] Example 5 A coating agent prepared by mixing the following liquids (1) and (2) in a weight ratio of 6:4 was applied onto the gas barrier layer 30 by gravure coating and dried to form a coating layer 60 with a thickness of 0.4 μm. A heat seal layer 50 was then attached by dry lamination using a two-component curing polyurethane adhesive as the adhesive layer 40, and the gas barrier film 1 of Example 5 was produced in the same manner as in Example 2, except that the thickness of the gas barrier layer 30 made of silicon oxide (SiOx) was 25 nm. (1) Solution: 10.4 g of tetraethoxysilane was mixed with 89.6 g of hydrochloric acid (0.1 N), and the mixture was stirred for 30 minutes to hydrolyze the solution, resulting in a solid content of 3 wt% (SiO2 equivalent). (2) Liquid: 3 wt% polyvinyl alcohol solution in water / isopropyl alcohol (water:isopropyl alcohol weight ratio 90:10)

[0066] Example 6 The gas barrier film 1 of Example 6 was produced in the same manner as in Example 2, except that the adhesive layer 40 was formed by applying the following gas barrier adhesive A onto the gas barrier layer 30 by gravure coating and drying it, and then the adhesive layer 40 was laminated to the heat seal layer 50, and the thickness of the gas barrier layer 30 made of silicon oxide (SiOx) was 35 nm. Adhesive A, an epoxy adhesive, was prepared by mixing 23 parts by mass of a solvent made by mixing ethyl acetate and methanol in a mass ratio of 1:1 with 16 parts by mass of Maxieve C93T manufactured by Mitsubishi Gas Chemical Company, Inc. and 5 parts by mass of Maxieve M-100 manufactured by Mitsubishi Gas Chemical Company, Inc.

[0067] Example 7 A gas barrier film 1 of Example 7 was produced in the same manner as in Example 2, except that a gas barrier layer (9 nm thick) made of aluminum oxide (AlOx) was formed as the gas barrier layer 30 by electron beam evaporation.

[0068] Example 8 A gas barrier film 1 of Example 8 was produced in the same manner as in Example 3, except that a gas barrier layer (20 nm thick) made of aluminum oxide (AlOx) was formed as the gas barrier layer 30 by electron beam evaporation.

[0069] Example 9 A gas barrier film 1 of Example 9 was produced in the same manner as in Example 6, except that a gas barrier layer (3 nm thick) made of aluminum oxide (AlOx) was formed as the gas barrier layer 30 by electron beam evaporation.

[0070] Example 10 A gas barrier film 1 of Example 10 was produced in the same manner as in Example 2, except that a gas barrier layer 30 made of metallic aluminum (Al) (thickness: 10 nm) was formed by electron beam evaporation.

[0071] Example 11 The gas barrier film of Example 11 was produced in the same manner as in Example 2, except that hexamethyldisiloxane (HMDSO) was introduced into a vacuum chamber and a gas barrier layer (thickness: 30 nm) made of carbon-containing silicon oxide (SiOxCy) was formed by plasma CVD as the gas barrier layer 30.

[0072] Example 12 The gas barrier film 1 of Example 12 was produced in the same manner as in Example 2, except that monosilane (SiH4), ammonia (NH3), and nitrogen (N2) were introduced into a vacuum chamber and a gas barrier layer (30 nm thick) made of silicon nitride (SiNx) was formed by plasma CVD.

[0073] (Comparative Example 1) The gas barrier film of Comparative Example 1 was produced in the same manner as in Example 2, except that the substrate 10 used was a film (thickness 35 μm) that did not contain a resin layer mainly made of ethylene-vinyl alcohol copolymer (EVOH) but was composed only of a resin layer mainly made of polyethylene and had a crystallinity of 23.0%.

[0074] (Comparative Example 2) The gas barrier film of Comparative Example 2 was produced in the same manner as in Example 3, except that the substrate 10 did not include a resin layer mainly made of ethylene-vinyl alcohol copolymer (EVOH), but was composed only of a resin layer mainly made of polyethylene, and had a crystallinity of 14.9% (thickness: 32 μm), and the film thickness of the gas barrier layer 30 was 30 nm.

[0075] The evaluation items and measurement methods in each of the examples and comparative examples are shown below.

[0076] (Crystallization measurement of PE film and laminate) The crystallinity of the PE film and laminate was measured using a Rigaku X-ray diffractometer (ATX-G) and X-ray diffraction patterns were obtained using the out-of-plane method. The obtained X-ray diffraction patterns were separated into three peaks: amorphous PE, PE(110), and PE(200). The area intensity of each peak was analyzed to calculate the crystallinity.

[0077] (Gas barrier property evaluation of laminate) (Oxygen transmission rate: OTR) The oxygen permeability of the laminate was measured under conditions of 30° and 70% RH (relative humidity) by the Mocon method. (Water Vapor Transmission Rate: WVTR) The water vapor transmission rate of the laminate was measured under conditions of 40°C and 90% RH by the Mocon method.

[0078] The structure of the laminate and the evaluation results are shown in Table 1.

[0079] [Table 1]

[0080] In Examples 1 to 12, the substrate 10 had a resin layer mainly made of ethylene-vinyl alcohol copolymer (EVOH) laminated on at least one side thereof with a resin mainly made of polyethylene, and the crystallinity was less than 35%, confirming good gas barrier properties.

[0081] In Comparative Examples 1 and 2, the substrate 10 was a polyethylene film that did not contain a resin layer mainly composed of ethylene-vinyl alcohol copolymer (EVOH), and therefore the gas barrier properties were inferior to those of Examples 1 to 12.

[0082] The above describes one embodiment of the present invention and examples, but the specific configuration is not limited to this embodiment, and includes modifications and combinations of configurations within the scope that does not deviate from the gist of the present invention. [Industrial Applicability]

[0083] The gas barrier film of the present invention is highly recyclable as a polyethylene material, exhibits excellent gas barrier properties, and exhibits good tearability, and is therefore suitable for use primarily as a packaging material. [Explanation of symbols]

[0084] 1. Gas barrier film 10 Base material 10a Front page 10b Second side 11 First resin layer 12 Second resin layer 20 Pretreatment layer 30 Gas barrier layer 40 Adhesive layer 50 Heat seal layer 60 Covering layer

Claims

1. A base material mainly composed of polyethylene; a gas barrier layer laminated on a first surface, which is one surface of the substrate, The substrate is a first resin layer that constitutes the first surface and is mainly made of polyethylene; a second resin layer that is disposed closer to a second surface, which is the other surface of the base material, than the first resin layer and that is mainly composed of an ethylene-vinyl alcohol copolymer; The substrate has a crystallinity of less than 35% as calculated by the ratio of the crystalline peak area of ​​PE(110) to the crystalline peak area of ​​PE(200) to the total peak area when measured by 2θ / θ scan measurement using a parallel beam method of X-ray diffraction in the diffraction angle range of 10° to 30°. Gas barrier film.

2. No antiblocking agent is added to the first surface of the substrate. The gas barrier film according to claim 1 .

3. The gas barrier layer is an inorganic oxide layer. The gas barrier film according to claim 1 or 2.

4. the inorganic oxide layer contains any one of silicon oxide, silicon oxide containing carbon, silicon nitride, metallic aluminum, and aluminum oxide; The gas barrier film according to claim 3 .

5. a pretreatment layer provided between the substrate and the gas barrier layer; The gas barrier film according to claim 1 .

6. a heat seal layer is laminated via an adhesive on a surface of the gas barrier layer facing away from the substrate; The gas barrier film according to claim 1 .

7. The heat seal layer is low density polyethylene or linear low density polyethylene. The gas barrier film according to claim 6 .

8. The proportion of polyethylene in the gas barrier film is 90% by mass or more. The gas barrier film according to claim 1 .

9. The oxygen permeability of the gas barrier film is 3.0 cc / (m ２ ·day·atm) or less, and the water vapor permeability is 3.0 g / (m ２ ・day) or less, The gas barrier film according to any one of claims 1 to 8.

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