Gas barrier film and gas barrier laminate

Abstract

To provide a gas barrier film which exhibits superior transparency and gas barrier functionality and enables reduction of environmental burden.SOLUTION: A gas barrier film 1 comprises a substrate 10 containing polypropylene, a first gas barrier layer 20 which is composed of a metal or an inorganic oxide A and is directly formed on the substrate 10, and a second gas barrier layer 30 which is composed of an inorganic oxide B and is formed on the first gas barrier layer 20. The gas barrier film 1 has a total light transmittance (JIS-K-7361) of 80% or more.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a gas barrier film and a gas barrier laminate. The gas barrier film and the gas barrier laminate of the present invention are suitable for packaging foods, pharmaceuticals, precision electronic components, etc.

Background Art

[0002] In packaging materials used for packaging contents such as foods, non-foods, and pharmaceuticals, from the viewpoint of suppressing the deterioration of the contents and maintaining the functions and properties of the contents, oxygen, water vapor, and other gases that deteriorate the contents permeating through the packaging material are required to be blocked, and gas barrier properties are required. As a packaging material having gas barrier properties, a gas barrier film using a metal foil made of aluminum or the like, 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. These gas barrier films have gas barrier properties for oxygen, water vapor, etc., and also have transparency.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, from the perspective of suppressing the environmental load, the demand for gas barrier films using base films made of polyethylene (PE) or polypropylene (PP) has been increasing. Patent Document 1 also provides a laminate excellent in recyclability. However, in the configuration described in Patent Document 1, since there is a layer between the base material and the vapor deposition layer, there is an environmental load when manufacturing the gas barrier film, and there is room for further improvement in recyclability from the viewpoint of being a single material. In addition, Patent Document 2 proposes a film having adhesiveness by forming two layers in the vapor deposition process. However, it has been found that when polyethylene or polypropylene is used as the base material, the barrier property is insufficient.

[0006] In view of the above circumstances, an object of the present invention is to provide a gas barrier film excellent in transparency and gas barrier property and capable of suppressing the environmental load, and a gas barrier laminate including the gas barrier film.

Means for Solving the Problems

[0007] The first aspect of the present invention is a gas barrier film including a base material containing polypropylene, a first gas barrier layer made of a metal or inorganic oxide A formed directly on the base material, and a second gas barrier layer made of inorganic oxide B formed on the first gas barrier layer, and having a total light transmittance of 80% or more.

[0008] The second aspect of the present invention is a gas barrier laminate in which a heat seal layer containing polypropylene is laminated on the gas barrier film.

[0009] The third aspect of the present invention is a gas barrier laminate in which a printing base material is laminated on the gas barrier film.

Effects of the Invention

[0010] The gas barrier film according to the present invention is excellent in transparency and gas barrier property and can suppress the environmental load.

Brief Description of the Drawings

[0011]

Figure 1

Embodiments for Carrying Out the Invention

[0012] Hereinafter, an embodiment of the present invention will be described with reference to FIG. 1. FIG. 1 is a schematic cross-sectional view of a gas barrier laminate 100 according to the present embodiment. The gas barrier laminate 100 shown in FIG. 1 includes a gas barrier film 1, a heat seal layer 50, a printing substrate 70, and a printing layer 80. The gas barrier film 1 includes a substrate 10, a first gas barrier layer 20, a second gas barrier layer 30, and an oxygen barrier coating 40.

[0013] The substrate 10 is a resin film containing polypropylene. Polypropylene is the component (main component) that occupies the highest proportion in the substrate 10. The substrate 10 may be either an unstretched film or a stretched film. When using a stretched film, the stretching ratio is not particularly limited.

[0014] The thickness of the substrate 10 is not particularly limited. The substrate 10 can be a single-layer film or a multilayer film formed by laminating films with different properties in consideration of the use of packaging materials and the like. Considering the processability when forming the first gas barrier layer 20, the second gas barrier layer 30, the oxygen barrier coating 40, etc., the thickness of the substrate 10 is preferably in the range of 3 to 200 μm, particularly preferably 6 to 80 μm, in practical terms.

[0015] 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, ultraviolet absorbers, lubricants, slip agents, nucleating agents, antistatic agents, antifogging agents, pigments, and dyes. The AB agent may be either organic or inorganic. Any one of these additives may be used alone, or two or more of them may be used in combination. The content of the additive in the substrate 10 can be appropriately adjusted within a range that does not interfere with the effects of the present invention. Agents, antistatic agents, antifogging agents, pigments, and dyes. The AB agent may be either organic or inorganic. Any one of these additives may be used alone, or two or more of them may be used in combination. The content of the additive in the substrate 10 can be appropriately adjusted within a range that does not interfere with the effects of the present invention.

[0016] The first gas barrier layer 20 is made of a metal or an inorganic oxide A and is formed directly on the first surface 10a of the base material 10. The first gas barrier layer 20 made of a metal or an inorganic oxide A is a layer mainly composed of any one of aluminum, zinc, copper, and silver, and is a layer that exhibits barrier properties against predetermined gases such as oxygen and water vapor. It is desirable that the gas barrier film 1 after forming the first gas barrier layer 20 is transparent. Also, the first gas barrier layer 20 may be made transparent by oxidizing the film after forming the metal film. When the first gas barrier layer 20 is made of a metal, if it becomes thick, it may become opaque and the contents inside the package may not be visible. By directly forming the first gas barrier layer 20 on the base material 10, the surface smoothness can be improved and the surface free energy can be changed, improving the film growth of the second gas barrier layer 30 and enabling the improvement of the barrier properties. Plasma treatment may be performed on the first surface 10a of the base material 10 before forming the first gas barrier layer 20. The method of plasma treatment is not particularly limited. Plasma treatment that can be performed inline from the viewpoint of productivity is preferable. The plasma treatment is not particularly limited to glow discharge, arc discharge, ion beam, etc., and a magnet may be used to increase the plasma density. Also, the gas used for plasma treatment can be selected from any one or a plurality of oxygen, nitrogen, and argon.

[0017] The second gas barrier layer 30 is made of an inorganic oxide B and is formed on the first gas barrier layer 20. The second gas barrier layer 30 made of an inorganic oxide B is a layer mainly composed of silicon oxide, silicon oxide containing carbon, silicon nitride, aluminum oxide, magnesium oxide, or any one of them, and is a layer that exhibits barrier properties against predetermined gases such as oxygen and water vapor. The inorganic oxide B of the second gas barrier layer 30 may be the same as or different from the inorganic oxide A of the first gas barrier layer 20.

[0018] The thicknesses of the first gas barrier layer 20 and the second gas barrier layer 30 vary depending on the types, compositions, and film formation methods of the components used for the first gas barrier layer 20 and the second gas barrier layer 30. Generally, they can be appropriately set within the range of 3 to 300 nm. If the thickness of the first gas barrier layer 20 is less than 3 nm, a uniform film may not be obtained or the film thickness may not be sufficient, and the function of the second gas barrier layer 30 may not be fully exerted. If the thicknesses of the first gas barrier layer 20 and the second gas barrier layer 30 exceed 300 nm, cracks may occur due to external factors such as bending and stretching after film formation, resulting in the loss of barrier properties. Also, if the thicknesses of the first gas barrier layer 20 and the second gas barrier layer 30 exceed 50 nm, there is a risk of losing transparency. Moreover, the thickness of the oxide may cause cracks due to external factors such as bending and stretching after film formation, resulting in the loss of barrier properties. The total thickness of the first gas barrier layer 20 and the second gas barrier layer 30 is more preferably within the range of 6 to 150 nm.

[0019] There is no limitation on the formation methods of the first gas barrier layer 20 and the second gas barrier layer 30. For example, vacuum evaporation, plasma-activated evaporation, sputtering, ion plating, ion beam evaporation, plasma chemical vapor deposition (CVD), etc. can be used. By combining methods such as plasma assist method and ion beam assist method, the first gas barrier layer 20 and the second gas barrier layer 30 can be formed densely to improve the barrier properties and adhesion.

[0020] The oxygen barrier film 40 is formed on the second gas barrier layer 30. The oxygen barrier film 40 protects the first gas barrier layer 20 and the second gas barrier layer 30, and further enhances the barrier property of the gas barrier film 1. The oxygen barrier film 40 can use a coating layer such as a thermoplastic resin, a thermosetting resin, an ultraviolet curable resin, a metal alkoxide, a water-soluble polymer, a polycarboxylic acid-based polymer, a polyvalent metal compound, and a polyvalent metal salt of a carboxylic acid which is a reaction product of a polycarboxylic acid-based polymer and a polyvalent metal compound. In particular, a metal alkoxide and a water-soluble polymer having excellent oxygen barrier properties are preferable. This is formed using a coating agent mainly composed of an aqueous solution or a water / alcohol mixed solution containing a water-soluble polymer and one or more metal alkoxides or their hydrolysis products. For example, a coating agent is prepared by mixing a water-soluble polymer dissolved in an aqueous (water or water / alcohol mixed) solvent with a metal alkoxide that has been directly treated or previously hydrolyzed. After applying this coating agent onto the second gas barrier layer 30 and then drying, the oxygen barrier film 40 can be formed.

[0021] Each component contained in the coating agent for forming the oxygen barrier film 40 will be described in more detail. Examples of the water-soluble polymer used in the coating agent include polyvinyl alcohol (PVA), polyvinyl pyrrolidone, starch, methyl cellulose, carboxymethyl cellulose, sodium alginate, etc. In particular, it is preferable to use PVA because excellent gas barrier properties can be obtained. PVA is generally obtained by saponifying polyvinyl acetate. As PVA, either so-called partially saponified PVA with several tens of % of acetate groups remaining or completely saponified PVA with only a few % of acetate groups remaining can be used. PVA in the middle of both can also be used.

[0022] The metal alkoxide used as the coating agent is a compound represented by the general formula M(OR)n (M: metal such as Si or Al, R: alkyl group such as CH3 or C2H5). Specifically, examples include tetraethoxysilane [Si(OC2H5)4] and triisopropoxyaluminum Al[OCH(CH3)2]3. Examples of the silane coupling agent 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.

[0023] Examples of the coating method for the oxygen barrier film 40 include a casting method, a dipping method, a roll coating method, a gravure coating method, a screen printing method, a reverse coating method, a spray coating method, a kit coating method, a die coating method, a metering bar coating method, a combined chamber doctor coating method, a curtain coating method, etc.

[0024] The thickness of the oxygen barrier film 40 varies depending on the composition of the coating agent used, the coating conditions, etc., and is not particularly limited. However, when the film thickness after drying of the oxygen barrier film 40 is 0.01 μm or less, a uniform coating film may not be formed and sufficient gas barrier properties may not be obtained. When the film thickness after drying exceeds 50 μm, cracks are likely to occur in the oxygen barrier film 40. Therefore, a suitable thickness of the oxygen barrier film 40 is, for example, in the range of 0.01 to 50 μm. The optimum thickness of the oxygen barrier film 40 is, for example, in the range of 0.1 to 10 μm.

[0025] Note that the gas barrier film 1 may not contain, for example, the oxygen barrier film 40.

[0026] The gas barrier film 1 of the present embodiment having the above configuration exhibits high gas barrier properties, while the main resin component is polypropylene, and it is also easy to make the ratio of the main resin component in the gas barrier film 1 90% by mass or more. That is, the gas barrier film 1 can be configured as a highly recyclable single material.

[0027] The total light transmittance (JIS-K-7361) of the gas barrier film 1 of the present embodiment is 80% or more. The water vapor transmission rate measured under 40 °C and 90% RH of the gas barrier film 1 of the present embodiment is not particularly limited, but may be, for example, 1 g / (m 2 ·day) or less.

[0028] The heat seal layer 50 is a layer capable of heat fusion and is laminated on the above-described gas barrier film 1. In the gas barrier laminate 100 illustrated in FIG. 1, the heat seal layer 50 is formed on the first surface 10a side of the base material 10, that is, on the oxygen barrier coating 40 of the gas barrier film 1. Note that the heat seal layer 50 may be formed on the second surface 10b side of the base material 10, for example.

[0029] The heat seal layer 50 may contain polypropylene in the same manner as the base material 10 used for the gas barrier film 1. In this case, polypropylene may be the main component in the heat seal layer 50. Thereby, the gas barrier laminate 100 can be recycled. The thickness of the heat seal layer 50 can be determined according to the purpose, but can be, for example, about 50 to 200 μm. The heat seal layer 50 may be provided by bonding resin films by dry lamination using the adhesive 60A as illustrated in FIG. 1, or may be provided by extrusion lamination using a fluid resin. A barrier adhesive may be used as the adhesive 60A. When a barrier adhesive is used, the barrier property of the gas barrier laminate 100 can be further enhanced.

[0030] As the adhesive 60A, a known adhesive for dry lamination can be used. The adhesive for dry lamination is not particularly limited, and specifically, examples include two-component curable ester-based adhesives, ether-based adhesives, urethane-based adhesives, and the like.

[0031] In the gas barrier laminate 100 including the heat seal layer 50 described above, by heat-sealing two or one folded gas barrier laminate 100 with the heat seal layer 50 facing each other, a packaging material such as a packaging bag can be easily produced. Also in this case, by making the main resin component of the heat seal layer 50 the same as the main resin component of the base material 10 used for the gas barrier film 1, the packaging material can be made of a single material.

[0032] The printing substrate 70 is for providing a printing layer 80 described later. The printing substrate 70 is the same as the base material 10 of the gas barrier film 1. That is, the printing substrate 70 is, for example, a resin film mainly composed of polypropylene, similar to the base material 10. Since the main component of the printing substrate 70 is the same as that of the base material 10, the gas barrier laminate 100 can be recycled. The printing substrate 70 is laminated on the gas barrier film 1. In the gas barrier film 1 illustrated in FIG. 1, the printing substrate 70 is provided on the second surface 10b side of the base material 10. Note that the printing substrate 70 may be provided, for example, on the first surface 10a side of the base material 10 (on the oxygen barrier coating 40 in FIG. 1). In this case, the heat seal layer 50 may be provided, for example, on the second surface 10b side of the base material 10.

[0033] The printing layer 80 is provided on the printing substrate 70. In the gas barrier laminate 100 illustrated in FIG. 1, the printing layer 80 is provided on the surface of the printing substrate 70 facing the gas barrier film 1. Note that the printing layer 80 is not limited to being provided on the printing substrate 70, and may be provided, for example, on the base material 10 or the heat seal layer 50. Generally, the printing layer 80 is provided at a position visible from the outside of the gas barrier laminate 100 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 in consideration of printability on the film, design properties such as color tone, adhesion, and safety as a food container.

[0034] As the printing method for the printing layer 80, for example, a gravure printing method, an offset printing method, a gravure offset printing method, a flexographic printing method, an inkjet printing method, etc. can be used. Among them, the gravure printing method can be preferably used from the viewpoints of productivity and high definition of the pattern. Note that the printing layer 80 may be provided as appropriate according to the intended use, or may not be provided.

[0035] In order to enhance the adhesion of the printing layer 80, various pretreatment such as corona treatment, plasma treatment, and frame treatment, or a coating layer such as an easy-adhesion layer may be provided on the surface of the layer forming the printing layer 80.

[0036] In the gas barrier laminate 100 illustrated in FIG. 1, the printing substrate 70 provided with the printing layer 80 is bonded to the second surface 10b of the substrate 10 using the adhesive 60B. The adhesive 60B may be the same as the adhesive 60A used for bonding the heat-sealing layer 50 described above, for example. Note that the printing substrate 70 provided with the printing layer 80 may be bonded to the oxygen barrier film 40 using the adhesive 60A, for example. In this case, the heat-sealing layer 50 may be bonded to the second surface 10b of the substrate 10 using the adhesive 60B, for example.

[0037] As described above, in the gas barrier film 1 of the present embodiment, a first gas barrier layer 20 made of a metal or an inorganic oxide A and directly formed on the base material 10, and a second gas barrier layer 30 made of an inorganic oxide B and formed on the first gas barrier layer 20 are provided. Further, the total light transmittance (JIS-K-7361) of the gas barrier film 1 is 80% or more. Thereby, it becomes possible to provide the gas barrier film 1 excellent in transparency and gas barrier properties.

[0038] Further, in the gas barrier film 1 of the present embodiment, the base material 10 is mainly composed of polypropylene. Thereby, it becomes possible to provide the gas barrier film 1 capable of suppressing the environmental load.

[0039] Further, in the gas barrier film 1 of the present embodiment, the first gas barrier layer 20 contains aluminum (Al), and the second gas barrier layer 30 contains aluminum (Al) or silicon (Si). Thereby, it becomes possible to sufficiently ensure the gas barrier property of the gas barrier film 1.

[0040] Further, in the gas barrier film 1 of the present embodiment, the water vapor transmission rate measured at 40 ° C. and 90% RH is 1 g / m 2 ·day or less. Thereby, the gas barrier property of the gas barrier film 1 can be sufficiently ensured.

[0041] The gas barrier film of the present embodiment will be further described using examples and comparative examples. The present invention is not limited by the specific contents of the examples and comparative examples.

[0042] (Example 1) As the base material 10, a biaxially stretched polypropylene film (PP; ME-1 manufactured by Mitsui Chemicals Toagosei Co., Ltd.) was used. Aluminum (Al) was evaporated by an electron beam evaporation method in a vacuum apparatus, and a 5-nm-thick aluminum (Al) layer was formed as the first gas barrier layer 20 on the corona-treated surface of the base material 10. Subsequently, silicon oxide (SiO) was sublimated by an electron beam evaporation method, and a 30-nm-thick silicon oxide (SiOx) layer was formed as the second gas barrier layer 30 on the aluminum (Al) layer. Thus, the gas barrier film of Example 1 was produced.

[0043] (Example 2) A gas barrier film of Example 2 was produced in the same manner as in Example 1, except that the thickness of the aluminum (Al) layer was 10 nm.

[0044] (Comparative Example 1) A gas barrier film of Comparative Example 1 was produced in the same manner as in Example 1, except that the first gas barrier layer (aluminum (Al) layer) was not formed.

[0045] (Comparative Example 2) A gas barrier film of Comparative Example 2 was produced in the same manner as in Example 1, except that the thickness of the aluminum (Al) layer was 75 nm.

[0046] The following evaluations were performed on the gas barrier films of Examples 1 and 2 and Comparative Examples 1 and 2.

[0047] (Evaluation of Optical Performance after Formation of the Second Gas Barrier Layer) The total light transmittance (unit: %) of the gas barrier film produced by the above procedure was evaluated. The total light transmittance was measured using NDH2000 manufactured by Nippon Denshoku Industries Co., Ltd. in accordance with JIS K 7361-1.

[0048] (Evaluation of Gas Barrier Performance after Formation of the Second Gas Barrier Layer) The water vapor transmission rate (WVTR) (unit: g / m 2·day, measurement conditions: 40°C - 90% RH) were evaluated. PERMATRAN-W3 / 34 manufactured by Mocon was used for the measurement. The above results are shown in Table 1.

[0049]

Table 1

[0050] In the gas barrier films of Examples 1 and 2, the total light transmittance was 80% or more in both cases, and the water vapor transmission rate was 1 g / m 2 ·day or less, and it was confirmed that the transparency and gas barrier properties were sufficiently ensured. In the gas barrier film of Comparative Example 1, the total light transmittance was 80% or more, and the transparency was good. However, in the gas barrier film of Comparative Example 1, the water vapor transmission rate was 1 g / m 2 ·day or more, resulting in insufficient gas barrier properties. In the gas barrier film of Comparative Example 2, the water vapor transmission rate was 1 g / m 2 ·day, and the gas barrier properties were good. However, in the gas barrier film of Comparative Example 2, the total light transmittance was less than 80%, resulting in insufficient transparency.

[0051] As described above, one embodiment and examples of the present invention have been explained, but the specific configuration is not limited to this embodiment, and configurations such as changes and combinations within the scope not departing from the gist of the present invention are also included.

Explanation of Reference Numerals

[0052] 1 Gas barrier film 10 Substrate 20 First gas barrier layer 30 Second gas barrier layer 40 Oxygen barrier coating 50 Heat seal layer 70 Printing substrate 100 Gas barrier laminate

Claims

1. A base material containing polypropylene, A first gas barrier layer made of a metal or inorganic oxide A and formed directly on the base material, A second gas barrier layer made of an inorganic oxide B and formed on the first gas barrier layer, and comprising: A gas barrier film having a total light transmittance (JIS-K-7361) of 80% or more.

2. The first gas barrier layer contains aluminum (Al), The gas barrier film according to claim 1, wherein the second gas barrier layer contains aluminum (Al) or silicon (Si).

3. The gas barrier film according to claim 1, further comprising an oxygen barrier coating formed on the second gas barrier layer.

4. The gas barrier film according to claim 3, wherein the oxygen barrier coating contains at least one of a metal alkoxide and a hydrolyzate of a metal alkoxide and a water-soluble polymer.

5. The gas barrier film according to claim 1, having a water vapor permeability of 1 g / m ２ ·day or less when measured at 40°C and 90% RH.

6. A gas barrier laminate in which a heat seal layer containing polypropylene is laminated on the gas barrier film according to any one of claims 1 to 5.

7. A gas barrier laminate in which a printing substrate is laminated on the gas barrier film according to any one of claims 1 to 5.

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