gas barrier film

Abstract

A gas barrier film according to the present invention comprises: a substrate primarily composed of polyethylene or polypropylene; a gas barrier layer formed on the substrate; and a coating layer formed on the gas barrier layer. The elemental ratio O / C of oxygen and carbon in the substrate surface on which the gas barrier layer is formed is 0.03 or higher.

Description

Technical Field

[0001] The present invention relates to a gas barrier film and a method for producing the gas barrier film. The gas barrier film of the present invention is suitable for packaging foods, pharmaceuticals, precision electronic components, and the like. This application claims priority based on Japanese Patent Application No. 2019-143284 filed in Japan on August 2, 2019, and incorporates the content thereof herein.

Background Art

[0002] In packaging materials used for packaging foods, non-foods, pharmaceuticals, etc., from the viewpoint of suppressing the deterioration of the contents and maintaining their functions and properties, a gas barrier property that blocks oxygen, water vapor, and other gases that deteriorate the contents permeating through the packaging material may be required. As a packaging material having a gas barrier property, a gas barrier film using a metal foil such as aluminum, which is less affected by temperature, humidity, etc., as a gas barrier layer is known.

[0003] As another configuration of the gas barrier film, a film in which a vapor deposition film of an inorganic oxide such as silicon oxide or aluminum oxide is formed on a base film made of a polymer material by vacuum vapor deposition, sputtering, or the like is known (see, for example, Patent Document 1). These gas barrier films have transparency and gas barrier properties against oxygen, water vapor, etc. As the base film, a film made of polyethylene terephthalate (PET) is often used.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, there has been a growing demand for gas barrier films using polypropylene (PP) or polyethylene (PE) base films from the perspective of reducing environmental impact. Patent Document 1 also describes the use of PP or PE base films. However, the inventor's research revealed that gas barrier films made simply by forming a barrier layer on a PP or PE base film may not actually have sufficient resistance to hot water treatments such as boiling or retorting.

[0006] Based on the above circumstances, the present invention has high resistance to hot water treatment and also reduces environmental impact. We provide gas barrier films. The purpose is to achieve this. [Means for solving the problem]

[0007] A gas barrier film according to a first aspect of the present invention is Contains one of the following: polyethylene, propylene / ethylene copolymer, or propylene / ethylene / 1-butene terpolymer. Substrate and It comprises at least one of an inorganic substance, an inorganic oxide, an inorganic nitride, or an inorganic oxynitride, On the substrate directly The substrate comprises a formed gas barrier layer, a coating layer formed on the gas barrier layer, and a heat-sealable sealant layer bonded to the coating layer by an adhesive layer, wherein the elemental composition ratio of oxygen to carbon on the side where the gas barrier layer is formed is O / C The peel strength between the substrate and the gas barrier layer after hot water treatment at a temperature of 98°C or higher for 30 minutes or more is 1 N / 15 mm or higher in all cases: T-type peeling normal state, T-type peeling measurement site wet, 180° peeling normal state, and 180° peeling measurement site wet. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a gas barrier film that has high resistance to hot water treatment and also reduces environmental impact. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic cross-sectional view of a gas barrier film according to one embodiment of the present invention. [Figure 2] These are the C1s spectra of examples and comparative examples of the present invention. [Figure 3] These are the O1s spectra of examples and comparative examples of the present invention. [Modes for carrying out the invention]

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

[0012] The base material 10 is primarily composed of PP, PE, or polystyrene (PS) to minimize environmental impact. These three resins may be used individually or in combination of two or more. From the viewpoint of providing heat resistance, mechanical strength, and dimensional stability, the synthetic resin forming the base material 10 is preferably a homopolymer polymerized by polymerization alone. Furthermore, from the viewpoint of providing heat sealability and flexibility to the base material 10, copolymers or terpolymers copolymerized with ethylene or 1-butene may be used.

[0013] The base material 10 may be either an unstretched film or a stretched film. When using a stretched film, there are no particular restrictions on the stretching ratio. There are no particular restrictions on the thickness of the base material 10. The base material 10 may be a single-layer film or a multilayer film formed by laminating films with different properties, depending on the intended use of the packaging material. Considering the processability when forming the gas barrier layer 30, the coating layer 40, etc., the thickness of the base material 10 is practically preferably in the range of 3 to 200 μm, and particularly preferably in the range of 6 to 30 μm. Each layer, such as the gas barrier layer 30 or the coating layer 40 described later, formed on the substrate 10 may be formed on one side of the substrate 10 or on both sides of the substrate 10. Each layer may be formed on one side of the substrate 10, and various well-known additives and stabilizers, such as antistatic agents, UV inhibitors, plasticizers, and lubricants, may be applied to the opposite side.

[0014] In the base material 10, the surface 10a (hereinafter also referred to as the first surface 10a) on which at least the gas barrier layer 30 is formed has an element composition ratio O / C of oxygen and carbon of 0.03 or more by surface treatment. In the base material 10 mainly composed of the above-described material, when no surface treatment is performed, O / C is less than at least 0.03 and is almost zero, but by performing surface treatment, O / C becomes 0.03 or more. The inventor has found that when the gas barrier layer 30 is formed after setting O / C on the surface of the base material 10 to 0.03 or more, the adhesion between the base material 10 and the gas barrier layer 30 exhibits high resistance to hot water treatment. Details thereof will be described later.

[0015] The O / C on the surface of the base material 10 can be measured by measurement by X-ray photoelectron spectroscopy (XPS measurement (X-ray Photoelectron Spectroscopy)). XPS measurement can analyze the type and concentration of atoms in a depth region of several nm from the surface of the measured substance, the type and bonding state of atoms bonded to the atoms of the measured substance, and can obtain an elemental ratio, a functional group ratio, and the like. In the gas barrier film according to the present embodiment, XPS measurement of the surface of the base material 10 cannot be performed in a state where the gas barrier layer 30 having a thickness of 5 to 100 nm is present. Although it is conceivable to measure after removing the gas barrier layer by argon ion etching, since the surface of the base material 10 is also scraped, there is a high possibility that the measurement result is meaningless.

[0016] Therefore, in the O / C measurement in the present invention, XPS measurement is performed after removing the gas barrier layer 30 by another method. That is, when the gas barrier film 1 is immersed in treated water containing weakly alkaline amines, the gas barrier layer 30 can be removed without scraping the surface of the base material 10. The water contained in the treated water may be any of tap water, ion-exchanged water, distilled water, etc., and there is no particular limitation. Examples of the weakly alkaline amines include ammonia, triethanolamine, trimethanolamine, diethanolamine, triethylamine, trimethylamine, etc., and two or more of these may be contained. The concentration of the weakly alkaline amines is preferably in the range of 0.01% to 10%. If it is less than 0.01%, it takes a long time to remove the gas barrier layer 30. If it exceeds 10%, the surface of the base material 10 may be contaminated, and the propylene structure may be destroyed. The dipping conditions can be, for example, 50°C or higher for 5 minutes.

[0017] The gas barrier layer 30 is a layer containing at least one of an inorganic substance, an inorganic oxide, an inorganic nitride, and an inorganic oxynitride, and is a layer that exhibits barrier properties against a predetermined gas such as oxygen and water vapor. Examples of the inorganic substance that becomes the material of the gas barrier layer 30 include aluminum, silicon, magnesium, zirconium, titanium, niobium, etc. Further, the gas barrier layer 30 may contain any of aluminum, aluminum oxide, silicon oxide, or silicon oxide containing carbon. The gas barrier layer 30 may be either transparent or opaque.

[0018] The thickness of the gas barrier layer 30 varies depending on the type, composition, and film formation method of the inorganic compound used, but generally can be appropriately set 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 not be sufficient, and the function as a gas barrier layer may not be fully exhibited. If the thickness of the gas barrier layer 30 exceeds 300 nm, the gas barrier layer 30 becomes hard, and cracks may occur in the gas barrier layer 30 due to external factors such as bending and pulling after film formation, resulting in the loss of barrier properties. Therefore, the thickness of the gas barrier layer 30 is preferably within the range of 6 to 150 nm.

[0019] There are no restrictions on the method of forming the gas barrier layer 30; for example, vacuum deposition, sputtering, ion plating, ion beam, and plasma vapor deposition (CVD) can be used. By combining plasma-assisted or ion beam-assisted methods, the gas barrier layer can be formed more densely, improving its barrier properties and adhesion.

[0020] The coating layer 40 can further enhance the barrier properties of the gas barrier layer 30. The coating layer 40 is formed using a coating agent mainly composed of an aqueous solution or water / alcohol mixture containing (1) one or more metal alkoxides or their hydrolysates, and (2) a water-soluble polymer. For example, the coating agent is prepared by dissolving a water-soluble polymer in an aqueous solvent (water or water / alcohol mixture) and mixing the metal alkoxide directly or by pre-treating it by hydrolysis. After applying this coating agent onto the gas barrier layer 30, the coating layer 40 can be formed by drying.

[0021] The components of the coating agent used to form the protective layer 40 will be described in more detail below. Examples of water-soluble polymers used in coating agents include polyvinyl alcohol (PVA), polyvinylpyrrolidone, starch, methylcellulose, carboxymethylcellulose, and sodium alginate. PVA is particularly preferred because it provides excellent gas barrier properties. PVA is generally obtained by saponifying polyvinyl acetate. Both partially saponified PVA, in which several tens of percent of acetate groups remain, and fully saponified PVA, in which only a few percent of acetate groups remain, can be used. PVA intermediate between the two may also be used.

[0022] Metal alkoxides used as coating agents have the general formula M(OR)n(M: Si, Al metal, R: CH 3、These are compounds that can be represented by an alkyl group such as C2H5. Specifically, examples include tetraethoxysilane [Si(OC2H5)4] and triisopropoxyaluminum Al[OCH(CH3)2]3. Examples of silane coupling agents include compounds having an epoxy group such as 3-glycidoxypropyltrimethoxysilane, compounds having an amino group such as 3-aminopropyltrimethoxysilane, compounds having a mercapto group such as 3-mercaptopropyltrimethoxysilane, compounds having an isocyanate group such as 3-isocyanatetopropyltriethoxysilane, and tris-(3-trimethoxysilylpropyl)isocyanurate. There are no restrictions on the method of applying the coating agent; conventionally known methods such as dipping, roll coating, screen printing, spraying, and gravure printing can be appropriately selected.

[0023] The thickness of the coating layer 40 varies depending on the composition of the coating agent and the coating conditions, and there are no particular restrictions. However, if the drying thickness of the coating layer 40 is 0.01 μm or less, a uniform coating film may not be formed, and sufficient gas barrier properties may not be obtained. If the drying thickness exceeds 50 μm, cracks are more likely to occur in the coating layer 40. Therefore, a suitable thickness for the coating layer 40 is, for example, in the range of 0.01 to 50 μm. The optimal thickness for the coating layer 40 is, for example, in the range of 0.1 to 10 μm.

[0024] The sealant layer 60 is a layer that is joined by heat fusion when forming a bag-shaped packaging body or the like using the gas barrier film 1. Examples of materials for the sealant layer 60 include 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 crosslinked products thereof. The thickness of the sealant layer 60 is determined according to the purpose, but is, for example, in the range of 15 to 200 μm.

[0025] The adhesive layer 50 bonds the sealant layer 60 and the coating layer 40. By using the adhesive layer 50, the resin film that forms the sealant layer 60 and the substrate 10 on which the gas barrier layer 30 and the coating layer 40 are formed can be bonded together by dry lamination. An example of the material for the adhesive layer 50 is a two-component curing polyurethane adhesive. A printing layer, an intervening film, a sealant layer, etc., may be laminated on the coating layer 40 to form a packaging material.

[0026] A method for manufacturing the gas barrier film 1 of this embodiment having the above configuration will be described. First, one side of the substrate 10 (first surface 10a) is surface-treated to make the O / C ratio of the treated surface 0.03 or higher (first step). In the first step, numerous oxygen-containing bonds such as CO bonds and COO bonds are formed on the treated surface of the substrate 10.

[0027] Next, a gas barrier layer 30 is formed on the treated surface using an appropriate method (second step). In the second step, the inorganic compound that forms the gas barrier layer 30 firmly bonds with the oxygen-containing bonds present on the treated surface of the substrate 10. As a result, the gas barrier layer 30 and the substrate 10 exhibit high adhesion.

[0028] Next, the coating agent described above is applied to the gas barrier layer 30 and dried to form a coating layer 40 on the gas barrier layer (third step). Furthermore, by applying an adhesive to the coating layer 40 and bonding a resin film that will become the sealant layer 60 (fourth step), the gas barrier film 1 is completed.

[0029] In the gas barrier film 1 configured as described above, the presence of hydroxyl groups and carboxyl groups on the surface (first surface 10a) of the substrate 10 allows for the formation of chemical bonds such as hydrogen bonds and covalent bonds between the substrate 10 and the gas barrier layer 30, thus preventing a decrease in adhesion even after hot water treatment. As a result, good adhesion between the substrate 10 and the gas barrier layer 30 is maintained.

[0030] The gas barrier film of this embodiment will be further described using examples and comparative examples. The present invention is not limited in any way by the specific details of the examples and comparative examples.

[0031] (Example 1) A polypropylene film (20 μm thick) made of homopolymer was used as the substrate 10. Plasma treatment was performed on one side of the substrate 10 (first surface 10a) using glow discharge (output 230 W) inside a vacuum chamber. The atmosphere was oxygen gas (10 Pa). Next, while introducing oxygen into the same vacuum chamber, aluminum was evaporated, and a gas barrier layer 30 (10 nm thick) made of aluminum oxide was formed by electron beam deposition. Multiple sample films were prepared up to this point. One of these films was immersed in distilled water containing 1.0 wt% triethanolamine at 80°C for 5 minutes to remove the gas barrier layer, and then XPS measurement (described later) was performed on the treated surface (first surface 10a) of the substrate.

[0032] A coating agent, prepared by mixing liquids (1) and (2) below in a weight ratio of 6:4, was applied to the gas barrier layer 30 of the remaining sample film using the gravure coating method and dried to form a coating layer 40 with a thickness of 0.4 μm. (1) Solution: Add 89.6g of hydrochloric acid (0.1N) to 10.4g of tetraethoxysilane, stir for 30 minutes to hydrolyze, and obtain a hydrolyzed solution with a solid content of 3 wt% (in terms of SiO2). (2) Solution: 3 wt% polyvinyl alcohol solution (solvent was water / isopropyl alcohol (water:isopropyl alcohol weight ratio 90:10)).

[0033] Finally, using a two-component curing polyurethane adhesive, an unstretched polypropylene film (70 μm thick) that would become a sealant layer 60 was laminated onto the coating layer 40 by dry lamination to obtain the gas barrier film of Example 1.

[0034] (Example 2) A gas barrier film of Example 2 was prepared in the same manner as in Example 1, except that SiO was used as the deposition material and a 30 nm thick gas barrier layer 30 containing silicon oxide was formed. XPS measurements were also performed using the same procedure.

[0035] (Example 3) A gas barrier film of Example 3 was prepared in the same manner as in Example 1, except that hexamethyldisiloxane (HMDSO) was used as the vapor deposition material and a 30 nm thick gas barrier layer 30 containing carbon-containing silicon oxide was formed by plasma. XPS measurements were also performed using the same procedure.

[0036] (Example 4) The gas barrier film of Example 4 was prepared in the same manner as in Example 1, except that the plasma treatment output in the surface treatment was set to 350W. XPS measurements were also performed using the same procedure.

[0037] (Example 5) The gas barrier film of Example 5 was prepared in the same manner as in Example 2, except that the plasma treatment output in the surface treatment was set to 350W. XPS measurements were also performed using the same procedure.

[0038] (Example 6) Except for using a plasma treatment output of 350W in the surface treatment, the gas barrier film of Example 6 was prepared in the same manner as in Example 3. XPS measurements were also performed using the same procedure.

[0039] (Example 7) The gas barrier film of Example 7 was prepared in the same manner as in Example 1, except that the plasma treatment output in the surface treatment was set to 470W. XPS measurements were also performed using the same procedure.

[0040] (Example 8) The gas barrier film of Example 8 was prepared in the same manner as in Example 2, except that the plasma treatment output in the surface treatment was set to 470W. XPS measurements were also performed using the same procedure.

[0041] (Example 9) The gas barrier film of Example 9 was prepared in the same manner as in Example 3, except that the plasma treatment output in the surface treatment was set to 470W. XPS measurements were also performed using the same procedure.

[0042] (Example 10) Except for setting the plasma output in the surface treatment to 930W, the gas barrier film of Example 10 was prepared in the same manner as in Example 1. XPS measurements were also performed using the same procedure.

[0043] (Example 11) The gas barrier film of Example 11 was prepared in the same manner as in Example 2, except that the plasma treatment output in the surface treatment was set to 930W. XPS measurements were also performed using the same procedure.

[0044] (Example 12) Except for setting the plasma output in the surface treatment to 930W, the gas barrier film of Example 12 was prepared in the same manner as in Example 3. XPS measurements were also performed using the same procedure.

[0045] (Example 13) The gas barrier film of Example 13 was prepared in the same manner as in Example 1, except that a polypropylene film (copolymer) containing ethylene was used as the base material. XPS measurements were also performed using the same procedure.

[0046] (Example 14) The gas barrier film of Example 14 was prepared in the same manner as in Example 2, except that a polypropylene film (copolymer) containing ethylene was used as the base material. XPS measurements were also performed using the same procedure.

[0047] (Example 15) The gas barrier film of Example 15 was prepared in the same manner as in Example 3, except that a polypropylene film (copolymer) containing ethylene was used as the base material. XPS measurements were also performed using the same procedure.

[0048] (Example 16) The gas barrier film of Example 16 was prepared in the same manner as in Example 1, except that a polypropylene film (terpolymer) containing ethylene and 1-butene was used as the base material. XPS measurements were also performed using the same procedure.

[0049] (Example 17) The gas barrier film of Example 17 was prepared in the same manner as in Example 2, except that a polypropylene film (terpolymer) containing ethylene and 1-butene was used as the base material. XPS measurements were also performed using the same procedure.

[0050] (Example 18) The gas barrier film of Example 18 was prepared in the same manner as in Example 3, except that a polypropylene film (terpolymer) containing ethylene and 1-butene was used as the base material. XPS measurements were also performed using the same procedure.

[0051] (Example 19) The gas barrier film of Example 19 was prepared in the same manner as in Example 2, except that a low-density polyethylene film (25 μm thick) was used as the substrate. XPS measurements were also performed using the same procedure.

[0052] (Example 20) The gas barrier film of Example 20 was prepared in the same manner as in Example 19, except that a high-density polyethylene film was used as the base material. XPS measurements were also performed using the same procedure.

[0053] (Example 21) The gas barrier film of Example 20 was prepared in the same manner as in Example 19, except that a high-density polyethylene film (copolymer) containing 1-butene was used as the base material. XPS measurements were also performed using the same procedure.

[0054] (Comparative Example 1) A gas barrier film of Comparative Example 1 was prepared in the same manner as in Example 1, except that no surface treatment was performed on the substrate. XPS measurements were also performed using the same procedure.

[0055] (Comparative Example 2) A gas barrier film for Comparative Example 2 was prepared in the same manner as in Example 2, except that no surface treatment was performed on the substrate. XPS measurements were also performed using the same procedure.

[0056] (Comparative Example 3) A gas barrier film for Comparative Example 3 was prepared in the same manner as in Example 3, except that no surface treatment was performed on the substrate. XPS measurements were also performed using the same procedure.

[0057] (Comparative Example 4) A gas barrier film for Comparative Example 4 was prepared in the same manner as in Example 13, except that no surface treatment was performed on the substrate. XPS measurements were also performed using the same procedure.

[0058] (Comparative Example 5) A gas barrier film for Comparative Example 5 was prepared in the same manner as in Example 14, except that no surface treatment was performed on the substrate. XPS measurements were also performed using the same procedure.

[0059] (Comparative Example 6) A gas barrier film for Comparative Example 6 was prepared in the same manner as in Example 15, except that no surface treatment was performed on the substrate. XPS measurements were also performed using the same procedure.

[0060] (Comparative Example 7) A gas barrier film for Comparative Example 7 was prepared in the same manner as in Example 16, except that no surface treatment was performed on the substrate. XPS measurements were also performed using the same procedure.

[0061] (Comparative Example 8) A gas barrier film for Comparative Example 8 was prepared in the same manner as in Example 17, except that no surface treatment was performed on the substrate. XPS measurements were also performed using the same procedure.

[0062] (Comparative Example 9) A gas barrier film for Comparative Example 9 was prepared in the same manner as in Example 18, except that no surface treatment was performed on the substrate. XPS measurements were also performed using the same procedure.

[0063] (Comparative Example 10) A gas barrier film for Comparative Example 10 was prepared in the same manner as in Example 19, except that no surface treatment was performed on the substrate. XPS measurements were also performed using the same procedure.

[0064] (Comparative Example 11) A gas barrier film for Comparative Example 11 was prepared in the same manner as in Example 20, except that no surface treatment was performed on the substrate. XPS measurements were also performed using the same procedure.

[0065] (Comparative Example 12) A gas barrier film for Comparative Example 12 was prepared in the same manner as in Example 21, except that no surface treatment was performed on the substrate. XPS measurements were also performed using the same procedure.

[0066] (Comparative Example 13) A gas barrier film of Comparative Example 13 was prepared in the same manner as in Example 10, except that the substrate was surface-treated under an oxygen-free argon atmosphere. XPS measurements were also performed using the same procedure.

[0067] (Comparative Example 14) A gas barrier film of Comparative Example 14 was prepared in the same manner as in Example 11, except that the substrate was surface-treated under an oxygen-free argon atmosphere. XPS measurements were also performed using the same procedure.

[0068] (Comparative Example 15) A gas barrier film for Comparative Example 15 was prepared in the same manner as in Example 12, except that the substrate was surface-treated under an argon atmosphere without oxygen. XPS measurements were also performed using the same procedure.

[0069] The details of each evaluation item, including XPS measurement, are described below. (XPS measurement of the substrate surface) The first surface 10a of the substrate 10 of each sample was measured using an X-ray photoelectron spectrometer. A JPS-9010MX X-ray photoelectron spectrometer manufactured by JEOL Ltd. was used. A non-monochromatic MgKα (1253.6 eV) X-ray source was used, with an output of 100 W (10 kV-10 mA). In the quantitative analysis, calculations were performed using relative sensitivity factors of 2.28 for O1s and 1.00 for C1s. A mixed function of Gaussian and Lorentz functions was used for waveform separation analysis of the C1s waveform, and charge correction was performed by setting the CC bond peak originating from the benzene ring to 285.0 eV. In the obtained O1s spectrum, a baseline was drawn connecting the plots at 529 eV and 536 eV, and the area of ​​the region enclosed by the spectrum and baseline was calculated. In the C1s spectrum, a baseline was drawn connecting the plots at 282 eV and 288 eV, and the area of ​​the region enclosed by the spectrum and baseline was calculated. Based on these area values, the O / C ratio for each example was calculated. All XPS measurements were performed on surfaces exposed after the gas barrier layer was removed. Figure 2 shows the C1s spectra of Example 1 and Comparative Example 1, and Figure 3 shows the O1s spectra of Example 1 and Comparative Example 1.

[0070] (Evaluation of gas barrier layer adhesion after hot water treatment) Two gas barrier films for each example were stacked with the sealant layer 60 facing each other, and the three sides were joined by heat fusion to create pouches (packaging containers) for each example. After filling each pouch with water as the contents, the open side was sealed by heat fusion. Subsequently, a hot water treatment was performed, either by retort sterilization (121°C for 30 minutes) or boiling (98°C for 30 minutes). After hot water treatment, test specimens were cut from the parts of each pouch that had been in contact with the contents, in accordance with JIS Z1707. The peel strength between the substrate 10 and the gas barrier layer 30 was measured using an Orientec Tensilon universal tester RTC-1250 as an indicator of adhesion. Two types of measurements were performed: T-shaped peeling and 180° peeling, both under normal conditions (Dry) and with the measurement site wet.

[0071] (Evaluation of gas barrier performance after hot water treatment) After preparing and treating the pouches for each example created using the above procedure with hot water, the pouches were opened and the oxygen permeability of the gas barrier film was measured (unit: cc / m²). 2• day·atm, measurement conditions: 30℃-70%RH), and water vapor transmission (unit: g / m³) 2 The measurement conditions (40°C-90%RH) were evaluated for each day.

[0072] The results are shown in Table 1.

[0073] [Table 1]

[0074] In all of the gas barrier films in the examples, the O / C ratio of the treated surface was 0.03 or higher, and high adhesion between the substrate and the gas barrier layer was maintained even after hot water treatment. More specifically, even after hot water treatment at a temperature of 98°C or higher for 30 minutes or more, the peel strength (peel strength of T-shaped peel and peel strength of 180° peel) between the substrate and the gas barrier layer was 1 N / 15 mm or higher in both the normal (Dry) and wet (Wet) conditions, indicating high adhesion performance between the two layers. Furthermore, good gas barrier performance was observed even after hot water treatment.

[0075] On the other hand, the comparative gas barrier films all had an O / C ratio of less than 0.03 on the substrate surface. In all measurement conditions, the comparative gas barrier films had a peel strength of less than 1 N / 15 mm between the substrate and the gas barrier layer, indicating extremely low adhesion between the gas barrier layer and the substrate after hot water treatment, and easily resulting in delamination. The gas barrier performance after hot water treatment was also generally low.

[0076] Generally, it is believed that increasing the surface roughness of a substrate improves its adhesion to the gas barrier layer formed on top of it due to the anchoring effect. However, in Comparative Examples 13 to 15, despite the increased surface roughness of the substrate due to plasma treatment, the decrease in adhesion of the gas barrier layer after hot water treatment could not be suppressed. This demonstrates that when forming a gas barrier film using an environmentally friendly substrate, such as the substrate used in this embodiment, oxygen-containing bonds on the substrate surface play a crucial role in the adhesion between the substrate and the gas barrier layer, as well as in the resistance to hot water treatment in gas barrier performance. This is a finding that has been revealed for the first time in this invention.

[0077] Although one embodiment of the present invention and its examples have been described above, the specific configuration is not limited to this embodiment, and modifications and combinations of the configuration that do not depart from the spirit of the present invention are also included.

[0078] For example, in the gas barrier film of the present invention, the gas barrier layer and the coating layer may be provided on both sides of the substrate. In this case, the elemental composition ratio of oxygen to carbon (O / C) on both surfaces of the substrate may be 0.03 or more.

[0079] Furthermore, in the gas barrier film of the present invention, a printed layer may be provided at an appropriate position. In addition, an intervening film may be attached on the coating layer to impart desired physical properties to the gas barrier film, such as pinhole resistance, cold resistance, heat resistance, bag drop resistance, and tear resistance.

[0080] Furthermore, adhesive layers and sealant layers are not essential in the gas barrier film of the present invention. In other words, adhesive layers and sealant layers may be provided as needed, taking into consideration the specific application of the gas barrier film. [Explanation of Symbols]

[0081] 1. Gas barrier film 10 Base material 10a surface (1st surface) 30 Gas barrier layer 40 Covering layer 50 adhesive layer 60 sealant layer

Claims

1. A substrate comprising polyethylene, a propylene / ethylene copolymer, and a propylene / ethylene / 1-butene terpolymer, A gas barrier layer formed directly on the substrate, comprising at least one inorganic substance, inorganic oxide, inorganic nitride, or inorganic oxynitride, A coating layer formed on the gas barrier layer, A heat-sealable sealant layer is bonded to the coating layer by an adhesive layer, Equipped with, In the substrate, the elemental composition ratio of oxygen to carbon (O / C) on the side where the gas barrier layer is formed is 0.03 or more. After hot water treatment at a temperature of 98°C or higher for 30 minutes or more, the peel strength between the substrate and the gas barrier layer is 1 N / 15 mm or more in all cases: T-type peel condition, wet T-type peel measurement area, 180° peel condition, and wet 180° peel measurement area. Gas barrier film.

2. The gas barrier layer comprises any of aluminum, aluminum oxide, silicon oxide, or silicon oxide containing carbon. The gas barrier film according to claim 1.

3. The coating layer contains one or more alkoxides or their hydrolysates and a water-soluble polymer. The gas barrier film according to claim 1 or 2.

Images