Multilayer film and packaging

Abstract

To provide a multilayer film capable of acquiring easy-peeling properties for a package when used as a bottom material of the package.SOLUTION: A multilayer film 1 includes a sealant layer 11 and a substrate layer 12 formed on one face 11a of the sealant layer 11. The substrate layer 12 has direct contact with the sealant layer 11 and contains polyethylene of a melting point of 120°C or higher. The polyethylene has a content in the substrate layer 12 of 50 mass% or more relative to the total mass of the substrate layer 12 and a melt flow rate of 0.5-7 g / 10 min at 190°C measured in conformity to JIS K 7210. The sealant layer 11 contains a polypropylene-based resin and a polyethylene-based resin. The polypropylene-based resin has a content in the sealant layer 11 of 5-40 mass% relative to the total mass of the sealant layer 11.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a multilayer film and a package. [Background technology]

[0002] Conventionally, to improve the shelf life of food, gas-flushed packaging, in which an inert gas is filled in the food storage compartment, or vacuum packaging, in which gas remaining in the food storage compartment is vacuum-evacuated, has been used. For example, a known example of such packaging is a package in which food is packed into a base formed by a deep-drawing machine, and then the base or lid is sealed after filling with an inert gas or vacuum-evacuating. The base or lid is generally a composite multilayer film that has both sealability and easy-open properties.

[0003] On the other hand, as a composite multilayer film having both sealability and easy-open properties, an easy-open composite film is known, which is obtained by sequentially laminating a saponified ethylene-vinyl acetate copolymer resin layer, a polyamide resin layer, an adhesive resin layer, and a polypropylene resin layer (substrate layer), and further providing, on the polypropylene resin layer (substrate layer) side, a sealant layer which is a blend of two or more incompatible resins such as an ethylene-propylene random copolymer in which an ethylene component is copolymerized into a polypropylene resin, and a polyethylene resin (see Patent Documents 1 and 2).

[0004] When the easy-open composite films disclosed in Patent Documents 1 and 2 are used, for example, as a lid material film, the sealant layer undergoes cohesive failure when the resulting package is opened, allowing easy peeling. Such a sealant layer is also called an easy-peel layer because it ensures easy opening. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3642925 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-288793 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when the easy-open composite films disclosed in Patent Documents 1 and 2 are used as the base material for the above-mentioned gas replacement packaging or vacuum packaging, the peel strength becomes locally high, and the easy-peel property of the packaging is sometimes unstable. In particular, when a gas replacement packaging or vacuum packaging is constructed using a soft base material that does not contain a highly rigid resin such as polyethylene terephthalate, there is a problem in that the peel strength varies greatly.

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a multilayer film that, when used as a base material for a package, can achieve stable easy-peel properties in the package. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention employs the following configuration. [1] A multilayer film comprising a sealant layer and a base layer provided on one side of the sealant layer, the base layer being in direct contact with the sealant layer, the base layer comprising polyethylene having a melting point of 120°C or higher, the content of the polyethylene in the base layer being 50% by mass or higher relative to the total mass of the base layer, the melt flow rate of the polyethylene at 190°C measured in accordance with JIS K 7210 being 0.5 to 7 g / 10 min, the sealant layer comprising a polypropylene-based resin and a polyethylene-based resin, the content of the polypropylene-based resin in the sealant layer being 5 to 40% by mass relative to the total mass of the sealant layer. [2] The density of the polyethylene is 0.925 to 0.970 g / cm 3 The multilayer film according to [1], [3] The multilayer film according to [1] or [2], wherein the thickness of the substrate layer is 5 to 125 μm. [4] The multilayer film according to any one of [1] to [3], wherein the ratio of the thickness of the base layer to the thickness of the sealant layer is 80:20 to 20:80.

[0009] [5] The multilayer film according to any one of [1] to [4], wherein the multilayer film has a thickness of 60 to 350 μm. [6] The multilayer film according to any one of [1] to [5], wherein the haze of the multilayer film is more than 10% and not more than 20%. [7] The multilayer film according to any one of [1] to [6], wherein a laminate film having a linear low-density polyethylene layer as a sealant layer is used, and the sealant layer in the laminate film and the sealant layer in the multilayer film are heat-sealed under conditions of a sealing temperature of 150°C, a sealing time of 2 seconds, and a sealing pressure of 0.5 MPa, and the minimum and maximum values ​​of the thickness of the sealant layer in the multilayer film after the heat-sealing are determined, and the minimum and maximum values ​​are used to determine the minimum and maximum values ​​of the ratio of the thickness of the sealant layer in the multilayer film after the heat-sealing to the thickness of the sealant layer in the multilayer film before the heat-sealing, and the minimum value of the ratio is 60% or more and the maximum value of the ratio is 140% or less. [8] A package comprising a lid material and a base material, the base material being made of the multilayer film described in any one of [1] to [7], and the sealant layer in the multilayer film being disposed on the lid material side. [9] The package according to [8], wherein the peel strength between the lid material and the base material is 5 to 15 N / 15 mm. [Effects of the Invention]

[0010] According to the present invention, there is provided a multilayer film that, when used as a base material for a package, can achieve stable easy-peel properties in the package. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view schematically illustrating an example of a multilayer film according to one embodiment of the present invention. [Figure 2] 1 is a cross-sectional view schematically illustrating an example of a packaging body according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] <<Multilayer film>> One embodiment of the present invention provides a multilayer film comprising a sealant layer and a base layer provided on one side of the sealant layer, the base layer being in direct contact with the sealant layer, the base layer comprising polyethylene having a melting point of 120°C or higher, the content of the polyethylene in the base layer being 50% by mass or higher relative to the total mass of the base layer, the polyethylene having a melt flow rate at 190°C measured in accordance with JIS K 7210 of 0.5 to 7 g / 10 min, the sealant layer comprising a polypropylene-based resin and a polyethylene-based resin, the content of the polypropylene-based resin in the sealant layer being 5 to 40% by mass relative to the total mass of the sealant layer.

[0013] The substrate layer contains 50% by mass or more of polyethylene having a melting point of 120°C or higher and a melt flow rate at 190°C of 0.5 to 7 g / 10 min. This allows the substrate layer to be flexible without containing highly rigid resins such as polyethylene terephthalate, while still exhibiting high heat resistance and low fluidity when heated. When a package is produced by heat-sealing a multilayer film having such a substrate layer to a lid, excessive deformation, i.e., flow, of the substrate layer is suppressed. Furthermore, the multilayer film has such a substrate layer in direct contact with the sealant layer. When a package constructed using such a multilayer film is opened, a peel initiation point occurs within the sealant layer. As a result, unlike when the peel initiation point occurs at the intersection of the substrate layer and the sealant layer, a locally high peel strength is suppressed. Furthermore, the occurrence of peel initiation points within the sealant layer and the suppression of flow of the substrate layer result in stable easy-peel properties.

[0014] In this specification, unless otherwise specified, the melting point of a resin means the melting point measured by differential scanning calorimetry (DSC) in accordance with JIS K7121.

[0015] The present invention will be described in detail below with reference to the drawings. Note that the drawings used in the following description may show essential parts enlarged for the sake of convenience in order to make the features of the present invention easier to understand, and the dimensional proportions of each component may not necessarily be the same as in reality. First, the overall structure of the multilayer film of this embodiment will be described.

[0016] FIG. 1 is a cross-sectional view schematically illustrating an example of the multilayer film of the present embodiment. The multilayer film 1 shown here comprises a sealant layer 11 and a substrate layer 12 provided on one surface 11 a of the sealant layer 11 , with the substrate layer 12 being in direct contact with the sealant layer 11 . Furthermore, the multilayer film 1 has a tear-resistant layer 13, a gas barrier layer 14, and an impact-resistant layer 15 stacked in this order on a surface 12a of the base layer 12 opposite to the sealant layer 11 side. Furthermore, the multilayer film 1 includes an adhesive layer 16 between the substrate layer 12 and the tear-resistant layer 13 . That is, the multilayer film 1 is constructed by laminating a sealant layer 11, a base layer 12, an adhesive layer 16, a tear-resistant layer 13, a gas barrier layer 14, and an impact-resistant layer 15 in this order in the thickness direction, with the sealant layer 11 and the base layer 12 being in direct contact with each other. One surface 15 a of the impact-resistant layer 15 (the surface opposite to the tear-resistant layer 13 side) is one outermost surface of the multilayer film 1 . The other surface 11b of the sealant layer 11 is the other outermost surface of the multilayer film 1 and also serves as a sealing surface.

[0017] The base layer 12 contains polyethylene having a melting point of 120°C or higher, and the content of the polyethylene (polyethylene having a melting point of 120°C or higher) in the base layer 12 is 50% by mass or higher relative to the total mass of the base layer 12. The melt flow rate (MFR) of the polyethylene at 190° C., measured in accordance with JIS K 7210, is 0.5 to 7 g / 10 min. The sealant layer 11 contains a polypropylene-based resin and a polyethylene-based resin, and the content of the polypropylene-based resin in the sealant layer 11 is 5 to 40% by mass relative to the total mass of the sealant layer 11.

[0018] The multilayer film of this embodiment is not limited to the multilayer film 1, and may be a multilayer film 1 in which some of the configuration is changed, deleted, or added, within the scope of the spirit of the present invention. For example, the multilayer film of this embodiment only needs to have a sealant layer and a base layer, and the adhesive layer, tear-resistant layer, gas barrier layer, and impact-resistant layer are optional layers, and one or more of these may not be present. For example, the multilayer film of this embodiment may include a sealant layer, a substrate layer, an adhesive layer, a tear-resistant layer, a gas barrier layer, an impact-resistant layer, or other layers that do not fall under any of the above categories.

[0019] Next, the multilayer film of this embodiment will be described in more detail.

[0020] <Base material layer> The substrate layer (substrate layer 12 in the multilayer film 1 shown in FIG. 1) imparts flexibility to the multilayer film. The substrate layer is preferably transparent. The substrate layer contains polyethylene having a melting point of 120°C or higher.

[0021] The melting point of the polyethylene (PE) contained in the base layer is not particularly limited as long as it is 120° C. or higher, but is preferably 124° C. or higher, and more preferably 128° C. or higher. When the melting point of the polyethylene is equal to or higher than the lower limit, variations in peel strength are suppressed and easy-peel properties are stabilized in the packaging material described below.

[0022] In this specification, unless otherwise specified, the "polyethylene" contained in the base layer means the above-mentioned "polyethylene having a melting point of 120° C. or higher."

[0023] There is no particular upper limit to the melting point of the polyethylene contained in the base layer. For example, polyethylene having a melting point of 140° C. or less is preferred because it is easily available. The melting point of the polyethylene contained in the base layer may be, for example, any one of 120 to 140°C, 124 to 140°C, and 128 to 140°C.

[0024] The melt flow rate (MFR) at 190°C of the polyethylene (polyethylene having a melting point of 120°C or higher, contained in the base layer), measured in accordance with JIS K 7210, is 0.5 to 7 g / 10 min, and may be, for example, any of 0.5 to 6 g / 10 min, 0.5 to 4.5 g / 10 min, and 0.5 to 3 g / 10 min, any of 1.5 to 7 g / 10 min, 3 to 7 g / 10 min, and 4.5 to 7 g / 10 min, or any of 1.5 to 6 g / 10 min and 3 to 4.5 g / 10 min. When the melt flow rate is within this range, variations in peel strength are suppressed and easy-peel properties are stabilized in the packaging described below.

[0025] The density of the polyethylene contained in the base layer is 0.925 to 0.970 g / cm 3 For example, it is preferably 0.941 to 0.970 g / cm 3 , 0.925~0.958g / cm 3 , and 0.941 to 0.958 g / cm 3 It may be either of the following.

[0026] The classification of polyethylene by its density is defined, for example, in the old JIS K 6748: 1995. In this specification, polyethylene is classified by its density according to this definition. That is, in this specification, low density polyethylene (LDPE) is a polyethylene having a density of 0.91 g / cm 3 More than 0.93g / cm 3 It means polyethylene that is less than Medium density polyethylene (MDPE) has a density of 0.93 g / cm 3 More than 0.942g / cm 3 It means polyethylene that is less than High density polyethylene (HDPE) has a density of 0.942 g / cm 3 This means polyethylene having a molecular weight of 1000 or more. The polyethylene contained in the substrate layer is mainly classified as medium density polyethylene or high density polyethylene, with some being classified as low density polyethylene.

[0027] The base layer may contain only one type of polyethylene (polyethylene having a melting point of 120°C or higher), or two or more types. When two or more types are used, the combination and ratio thereof can be selected arbitrarily depending on the purpose.

[0028] In the base layer, the content of the polyethylene (polyethylene having a melting point of 120°C or higher) relative to the total mass of the base layer is not particularly limited as long as it is 50% by mass or higher. That is, the base layer may contain only the polyethylene (i.e., it may be a layer made of the polyethylene), or it may contain the polyethylene and other components together (i.e., it may be a layer made of the polyethylene and other components). This ratio is usually the same as the ratio of the content (parts by mass) of the polyethylene to the total content (parts by mass) of components that do not vaporize at room temperature in the composition for forming a base layer, which will be described later.

[0029] In this specification, "room temperature" means a temperature that is neither particularly cold nor hot, that is, an ordinary temperature, and examples thereof include temperatures of 15 to 25°C.

[0030] The other components contained in the base layer may be either resin components (sometimes referred to as "other resin components" in this specification) or non-resin components (sometimes referred to as "other non-resin components" in this specification).

[0031] The other resin component contained in the base layer is not particularly limited as long as it is a resin other than the polyethylene. Examples of the other resin component include polyethylene having a melting point of less than 120° C. and resins other than polyethylene.

[0032] Examples of the other non-resin components contained in the substrate layer include additives known in the art. Examples of the additives include antifogging agents, antiblocking agents, antioxidants, antistatic agents, crystal nucleating agents, inorganic particles, viscosity reducers, thickeners, heat stabilizers, lubricants, infrared absorbers, and ultraviolet absorbers.

[0033] The other components contained in the base layer may be one type only, or two or more types. When there are two or more types, the combination and ratio thereof can be selected arbitrarily depending on the purpose.

[0034] In the base layer, the content of the polyethylene (polyethylene having a melting point of 120°C or higher) relative to the total mass of the base layer may be, for example, 65% by mass or more, 80% by mass or more, or 95% by mass or more. When the content is equal to or more than the lower limit, variations in peel strength are suppressed and easy-peel properties are stabilized in the package described below. That is, in the base layer, the content of the other components relative to the total mass of the base layer is 50% by mass or less, and may be, for example, any one of 35% by mass or less, 20% by mass or less, and 5% by mass or less.

[0035] In the base layer, the content of the polyethylene (polyethylene having a melting point of 120° C. or higher) relative to the total mass of the base layer is 100 mass % or less. The proportion may be, for example, any one of 50 to 100 mass %, 65 to 100 mass %, 80 to 100 mass %, and 95 to 100 mass %.

[0036] The substrate layer may consist of one layer (single layer) or two or more layers. When the substrate layer consists of multiple layers, these multiple layers may be the same or different from each other, and the combination of these multiple layers is not particularly limited as long as it does not impair the effects of the present invention.

[0037] In this specification, not limited to the case of the base material layer, "multiple layers may be the same or different from one another" means "all layers may be the same, all layers may be different, or only some layers may be the same," and further, "multiple layers are different from one another" means "at least one of the constituent materials and thicknesses of each layer is different from one another."

[0038] The thickness of the substrate layer is preferably 5 to 125 μm, and may be, for example, any one of 5 to 100 μm, 5 to 75 μm, and 5 to 50 μm, any one of 25 to 125 μm, 45 to 125 μm, and 65 to 125 μm, or any one of 25 to 100 μm and 45 to 75 μm. When the thickness of the substrate layer is equal to or greater than the lower limit, the mechanical strength of the substrate layer is increased. When the thickness of the substrate layer is equal to or less than the upper limit, the transparency of the substrate layer and the multilayer film is increased. When the substrate layer is made up of a plurality of layers, the total thickness of these layers is preferably within the above-mentioned range.

[0039] <Sealant layer> The sealant layer (sealant layer 11 in the multilayer film 1 shown in FIG. 1) is one of the outermost layers of the multilayer film, and provides the multilayer film with sufficient sealing properties and good easy-peel properties. The sealant layer is preferably transparent. The substrate layer is in direct contact with the sealant layer. The sealant layer contains a polypropylene-based resin and a polyethylene-based resin, and thus has easy-peel properties.

[0040] The polypropylene resin contained in the sealant layer is not particularly limited as long as it is a resin having a structural unit derived from propylene.

[0041] Examples of the polypropylene resin contained in the sealant layer include a propylene homopolymer (that is, homopolypropylene, sometimes referred to as "hPP" in this specification) and a propylene copolymer.

[0042] The propylene-based copolymer has structural units derived from propylene and structural units derived from a monomer other than propylene. Examples of the propylene copolymer include propylene-ethylene random copolymer (also known as polypropylene random copolymer, also referred to as "rPP"), propylene-ethylene block copolymer (also known as polypropylene block copolymer, also referred to as "bPP"), and propylene-butene copolymer.

[0043] The sealant layer may contain only one type of polypropylene resin or two or more types, and when two or more types are contained, the combination and ratio thereof can be selected arbitrarily depending on the purpose. For example, the sealant layer may contain a propylene homopolymer but not a propylene copolymer, may contain one or more propylene copolymers but not a propylene homopolymer, or may contain a propylene homopolymer but not one or more propylene copolymers.

[0044] The polypropylene resin contained in the sealant layer is preferably a propylene homopolymer (homopolypropylene (hPP)).

[0045] The polyethylene resin contained in the sealant layer is not particularly limited as long as it is a resin having a structural unit derived from ethylene.

[0046] The polyethylene resin contained in the sealant layer includes an ethylene homopolymer (ie, polyethylene (PE)) and an ethylene copolymer.

[0047] Examples of the ethylene homopolymer include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE, for example, metallocene-catalyzed linear low-density polyethylene (mLLDPE)), medium-density polyethylene (MDPE), and high-density polyethylene (HDPE).

[0048] The ethylene copolymer has structural units derived from ethylene and structural units derived from a monomer other than ethylene. Examples of the ethylene copolymer include ethylene-vinyl acetate copolymer (EVA resin), ethylene-methyl acrylate copolymer (EMA resin), ethylene-methyl methacrylate copolymer (EMMA resin), ethylene-ethyl acrylate copolymer (EEA resin), ethylene-acrylic acid copolymer (EAA resin), ethylene-methacrylic acid copolymer (EMAA resin), ethylene-ethyl acrylate-maleic anhydride copolymer (E-EA-MAH resin), and ionomer resin (ION resin). The ionomer resin may be, for example, a resin in which a copolymer of ethylene and a small amount of acrylic acid or methacrylic acid has an ionic crosslinking structure due to salt formation between the acid moiety in the copolymer and a metal ion.

[0049] The sealant layer may contain only one type of polyethylene-based resin or two or more types, and when two or more types are contained, the combination and ratio thereof can be selected arbitrarily depending on the purpose. For example, the sealant layer may contain one or two or more types of polyethylene and no ethylene-based copolymer, or may contain one or two or more types of ethylene-based copolymer and no polyethylene, or may contain one or two or more types of polyethylene and one or two or more types of ethylene-based copolymer.

[0050] The polyethylene resin contained in the sealant layer is preferably polyethylene (PE), and more preferably low-density polyethylene (LDPE).

[0051] In the sealant layer, the content of the polypropylene resin relative to the total mass of the sealant layer is 5 to 40 mass %. By keeping the content within this range, variations in peel strength are suppressed and easy-peel properties are stabilized in the package described below. The ratio is usually the same as the ratio of the content (parts by mass) of the polypropylene resin to the total content (parts by mass) of components that do not vaporize at room temperature in the sealant layer-forming composition described below.

[0052] In order to obtain the above-mentioned effects more significantly, the content ratio of the polypropylene resin in the sealant layer relative to the total mass of the sealant layer may be, for example, any one of 5 to 30 mass% and 5 to 20 mass%, or any one of 15 to 40 mass% and 25 to 40 mass%, or may be 15 to 30 mass%.

[0053] In the sealant layer, the content of the polyethylene resin relative to the total mass of the sealant layer is preferably 60 to 95% by mass, and may be, for example, any of 70 to 95% by mass, 80 to 95% by mass, 60 to 85% by mass, 60 to 75% by mass, or 70 to 85% by mass. When the content is within this range, variations in peel strength are further suppressed and easy-peel properties are more stable in the package described below. The ratio is usually the same as the ratio of the content (parts by mass) of the polyethylene resin to the total content (parts by mass) of components that do not vaporize at room temperature in the sealant layer-forming composition described below.

[0054] The sealant layer may contain only the polypropylene-based resin and the polyethylene-based resin (i.e., it may be a layer consisting of the polypropylene-based resin and the polyethylene-based resin), or it may contain the polypropylene-based resin and the polyethylene-based resin, and further contain other components that do not fall into either of these categories (the polypropylene-based resin and the polyethylene-based resin) (i.e., it may be a layer consisting of the polypropylene-based resin, the polyethylene-based resin, and other components).

[0055] The other components contained in the sealant layer may be either resin components (sometimes referred to in this specification as "other resin components") or non-resin components (sometimes referred to in this specification as "other non-resin components").

[0056] The other resin component contained in the sealant layer is not particularly limited as long as it is a resin that does not fall into either the polypropylene-based resin or the polyethylene-based resin.

[0057] Examples of the other non-resin components contained in the sealant layer include additives known in the art. Examples of the additives include the same additives as those contained in the base layer.

[0058] The sealant layer may contain only one type of other component, or two or more types. When there are two or more types, the combination and ratio thereof can be selected arbitrarily depending on the purpose.

[0059] A preferred example of the other components contained in the sealant layer is an anti-fogging agent.

[0060] In the sealant layer, the proportion of the total content of the polypropylene-based resin and the polyethylene-based resin relative to the total mass of the sealant layer is preferably 80% by mass or more, and may be, for example, 85% by mass or more, 90% by mass or more, or 95% by mass or more. When this proportion is equal to or greater than the lower limit, variation in peel strength is suppressed and easy-peel properties are stabilized in the package described below. That is, in the sealant layer, the content of the other components relative to the total mass of the sealant layer is preferably 20% by mass or less, and may be, for example, any of 15% by mass or less, 10% by mass or less, and 5% by mass or less. The ratio of the total content is usually the same as the ratio of the total content (parts by mass) of the polypropylene-based resin and polyethylene-based resin to the total content (parts by mass) of components that do not vaporize at room temperature in the composition for forming the sealant layer described below.

[0061] The sealant layer may consist of one layer (single layer) or two or more layers. When the sealant layer consists of multiple layers, these multiple layers may be the same or different, and the combination of these multiple layers is not particularly limited as long as it does not impair the effects of the present invention.

[0062] In the multilayer film, the ratio of [thickness of base layer]:[thickness of sealant layer] is preferably 80:20 to 20:80, and may be, for example, any of 80:20 to 60:40, 40:60 to 20:80, and 65:35 to 35:65. When the ratio is in this range, variations in peel strength are further suppressed and easy-peel properties are more stable in the package described below. Here, the "thickness of the base layer" refers to the total thickness of the multiple layers when the base layer is made up of multiple layers. Similarly, the "thickness of the sealant layer" refers to the total thickness of the multiple layers when the sealant layer is made up of multiple layers.

[0063] The thickness of the sealant layer is preferably within a numerical range that satisfies the ratio of [thickness of base layer]:[thickness of sealant layer] described above. For example, the thickness of the sealant layer is preferably 5 to 125 μm. When the thickness of the sealant layer is equal to or greater than the lower limit, the mechanical strength of the sealant layer is increased. When the thickness of the sealant layer is equal to or less than the upper limit, the transparency of the sealant layer and the multilayer film is increased. When the sealant layer is made up of multiple layers, the total thickness of these multiple layers preferably falls within the above-mentioned range.

[0064] <Tear-resistant layer> The multilayer film may further include a tear-resistant layer (tear-resistant layer 13 in the multilayer film 1 shown in FIG. 1) on the surface of the substrate layer opposite to the sealant layer side. The tear resistant layer provides tear resistance to the multilayer film. The tear resistant layer is preferably transparent. The tear-resistant layer is preferably a resin layer containing a resin.

[0065] A preferred example of the resin contained in the tear-resistant layer is polyamide.

[0066] Examples of the polyamide include polyamides obtained by polymerizing or copolymerizing nylon salts, which are reaction products of cyclic lactams (lactams having 3 or more ring members), amino acids, or diamines and dicarboxylic acids.

[0067] Examples of the cyclic lactam include ε-caprolactam, ω-enantholactam, ω-laurolactam, α-pyrrolidone, and α-piperidone.

[0068] Examples of the amino acid include 6-aminocaproic acid, 7-aminoheptanoic acid, 9-aminononanoic acid, 11-aminoundecanoic acid, and 12-aminododecanoic acid.

[0069] Examples of the diamine that forms the nylon salt include aliphatic amines such as tetramethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, undecamethylenediamine, dodecamethylenediamine, 2,2,4-trimethylhexamethylenediamine, and 2,4,4-trimethylhexamethylenediamine; Alicyclic diamines such as 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, isophoronediamine, piperazine, bis(4-aminocyclohexyl)methane, and 2,2-bis-(4-aminocyclohexyl)propane; Examples include aromatic diamines such as metaxylylenediamine and paraxylylenediamine.

[0070] Examples of the dicarboxylic acid that forms the nylon salt include aliphatic dicarboxylic acids such as glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sepatic acid, undecanedioic acid, and dodecanedioic acid; Alicyclic carboxylic acids such as hexahydroterephthalic acid and hexahydroisophthalic acid; Examples of aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, 1,2-naphthalenedicarboxylic acid, 1,3-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 1,6-naphthalenedicarboxylic acid, 1,7-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 2,7-naphthalenedicarboxylic acid.

[0071] More specifically, the polyamides include, for example, 4-nylon, 6-nylon, 7-nylon, 11-nylon, 12-nylon, 46-nylon, 66-nylon, 69-nylon, 610-nylon, 611-nylon, 612-nylon, 6T-nylon, 6I nylon, a copolymer of 6-nylon and 66-nylon (nylon 6 / 66), a copolymer of 6-nylon and 610-nylon, a copolymer of 6-nylon and 611-nylon, a copolymer of 6-nylon and 12-nylon (nylon 6 / 12), and a copolymer of 6-nylon and 612 nylon. copolymers of 6-nylon and 6T-nylon, copolymers of 6-nylon and 6I-nylon, copolymers of 6-nylon and 66-nylon to form 610-nylon, copolymers of 6-nylon and 66-nylon to form 12-nylon (nylon 6 / 66 / 12), copolymers of 6-nylon, 66-nylon and 612-nylon, copolymers of 66-nylon and 6T-nylon, copolymers of 66-nylon and 6I-nylon, copolymers of 6T-nylon and 6I-nylon, copolymers of 66-nylon, 6T-nylon and 6I-nylon, and copolymers of 66-nylon, 6T-nylon and 6I-nylon.

[0072] In terms of heat resistance, mechanical strength, availability, etc., the polyamide is preferably 6-nylon, 12-nylon, 66-nylon, nylon 6 / 66, nylon 6 / 12, or nylon 6 / 66 / 12.

[0073] The tear-resistant layer may contain only one type of resin or two or more types, and when two or more types are contained, the combination and ratio thereof can be selected arbitrarily depending on the purpose. For example, the tear-resistant layer may contain one or more types of polyamide and no resin other than polyamide, or may contain one or more types of resin other than polyamide and no polyamide, or may contain one or more types of polyamide and one or more types of resin other than polyamide.

[0074] The tear-resistant layer may contain only the resin (i.e., it may be a layer made of the resin), or it may contain both the resin and other components (in other words, non-resin components) (i.e., it may be a layer made of the resin and other components).

[0075] Examples of the other components (non-resin components) contained in the tear-resistant layer include additives known in the art. Examples of the additives include the same additives as those contained in the base layer.

[0076] The tear-resistant layer may contain only one type of other component, or two or more types. When two or more types are contained, the combination and ratio thereof can be selected arbitrarily depending on the purpose.

[0077] In the tear-resistant layer, the content of the resin relative to the total mass of the tear-resistant layer is preferably 80% by mass or more, and may be, for example, 85% by mass or more, 90% by mass or more, or 95% by mass or more. When the content is equal to or more than the lower limit, the tear resistance of the multilayer film and the tear-resistant layer is further increased. That is, in the tear-resistant layer, the content of the other components (non-resin components) relative to the total mass of the tear-resistant layer is preferably 20% by mass or less, and may be, for example, 15% by mass or less, 10% by mass or less, or 5% by mass or less. The content ratio of the resin is usually the same as the ratio of the content (parts by mass) of the resin to the total content (parts by mass) of components that do not vaporize at room temperature in the composition for forming the tear-resistant layer described below.

[0078] In the tear-resistant layer, the content of the resin relative to the total mass of the tear-resistant layer is 100% by mass or less. The proportion may be, for example, any one of 85 to 100 mass %, 90 to 100 mass %, and 95 to 100 mass %.

[0079] When the tear-resistant layer contains the polyamide, the ratio of the polyamide content to the resin content in the tear-resistant layer is preferably 80% by mass or more, and may be, for example, 85% by mass or more, 90% by mass or more, or 95% by mass or more. When the ratio is equal to or greater than the lower limit, the tear resistance of the multilayer film and the tear-resistant layer is further increased. That is, in the tear-resistant layer, the ratio of the content of resins other than the polyamide to the content of the resin is preferably 20% by mass or less, and may be, for example, 15% by mass or less, 10% by mass or less, or 5% by mass or less. The content ratio of the polyamide is usually the same as the ratio of the content (parts by mass) of the polyamide to the content (parts by mass) of the resin in the composition for forming a tear-resistant layer, which will be described later.

[0080] In the tear-resistant layer, the ratio of the content of the polyamide to the content of the resin is 100% by mass or less. The proportion may be, for example, any one of 85 to 100 mass %, 90 to 100 mass %, and 95 to 100 mass %.

[0081] The tear-resistant layer may be composed of one layer (single layer) or two or more layers. When the tear-resistant layer is composed of multiple layers, these multiple layers may be the same or different from each other, and the combination of these multiple layers is not particularly limited as long as it does not impair the effects of the present invention.

[0082] The thickness of the tear-resistant layer is not particularly limited, but is preferably 5 μm or more, more preferably 10 μm or more. When the thickness of the tear-resistant layer is equal to or greater than the lower limit, the tear resistance of the multilayer film and the tear-resistant layer is increased. There is no particular upper limit to the thickness of the tear-resistant layer, either. For example, the tear-resistant layer is preferably 100 μm or less in order to avoid excessive thickness. The thickness of the tear-resistant layer may be, for example, either 5 to 100 μm or 10 to 100 μm. When the tear-resistant layer is made up of multiple layers, the total thickness of these multiple layers preferably falls within the above-mentioned range.

[0083] <Gas barrier layer> The multilayer film may further include a gas barrier layer (gas barrier layer 14 in the multilayer film 1 shown in FIG. 1) on the surface of the tear-resistant layer opposite to the substrate layer side. The gas barrier layer imparts gas barrier properties to the multilayer film. The gas barrier layer is preferably transparent. The gas barrier layer is preferably a resin layer containing a resin.

[0084] Preferred examples of the resin contained in the gas barrier layer include resins (sometimes referred to herein as "vinyl resins") that can be considered to have structural units derived from monomers having vinyl groups (sometimes referred to herein as "vinyl group-containing monomers"), such as polyvinylidene chloride (PVDC), polyvinyl alcohol (PVOH), and ethylene-vinyl alcohol copolymer (also known as saponified ethylene-vinyl acetate copolymer, EVOH); polyesters such as polyethylene terephthalate (PET), and aromatic polyamides such as polymetaxylylene adipamide (MXD6). These resins are suitable as resins that exhibit oxygen barrier properties (resins that constitute the oxygen barrier layer, sometimes referred to herein as "oxygen barrier resins").

[0085] In the ethylene-vinyl alcohol copolymer (EVOH), the ratio of the amount (moles) of structural units derived from ethylene to the total amount (moles) of structural units (sometimes referred to herein as the "ethylene content") is preferably 20 to 50 mol%, more preferably 25 to 45 mol%, and even more preferably 30 to 40 mol%. When the ethylene content of the ethylene-vinyl alcohol copolymer is within this range, the gas barrier properties of the multilayer film and the gas barrier layer are improved without impairing properties other than the gas barrier properties of the multilayer film.

[0086] The gas barrier layer may contain only one type of resin, or two or more types, and when two or more types are used, the combination and ratio thereof can be selected as desired depending on the purpose. For example, the gas barrier layer may contain one or more types of oxygen barrier resins and no resins other than the oxygen barrier resins, or may contain one or more types of resins other than the oxygen barrier resins and no oxygen barrier resins, or may contain one or more types of oxygen barrier resins and one or more types of resins other than the oxygen barrier resins.

[0087] The resin contained in the gas barrier layer is preferably an ethylene-vinyl alcohol copolymer (EVOH).

[0088] The gas barrier layer may contain only the resin (i.e., it may be a layer made of the resin), or it may contain both the resin and other components (in other words, non-resin components) (i.e., it may be a layer made of the resin and other components).

[0089] Examples of the other components (non-resin components) contained in the gas barrier layer include additives known in the art. Examples of the additives include the same additives as those contained in the base layer.

[0090] The gas barrier layer may contain only one type of other component, or two or more types. When two or more types are contained, the combination and ratio thereof can be selected arbitrarily depending on the purpose.

[0091] In the gas barrier layer, the content of the resin relative to the total mass of the gas barrier layer is preferably 80% by mass or more, and may be, for example, 85% by mass or more, 90% by mass or more, or 95% by mass or more. When the content is equal to or more than the lower limit, the gas barrier properties of the multilayer film and the gas barrier layer are further improved. That is, in the gas barrier layer, the content of the other components (non-resin components) relative to the total mass of the gas barrier layer is preferably 20 mass% or less, and may be, for example, 15 mass% or less, 10 mass% or less, or 5 mass% or less. The content ratio of the resin is usually the same as the ratio of the content (parts by mass) of the resin to the total content (parts by mass) of components that do not vaporize at room temperature in the composition for forming a gas barrier layer described below.

[0092] In the gas barrier layer, the content of the resin relative to the total mass of the gas barrier layer is 100 mass % or less. The proportion may be, for example, any one of 85 to 100 mass %, 90 to 100 mass %, and 95 to 100 mass %.

[0093] When the gas barrier layer contains the oxygen barrier resin, the ratio of the content of the oxygen barrier resin to the content of the resin in the gas barrier layer is preferably 80% by mass or more, and may be, for example, 85% by mass or more, 90% by mass or more, or 95% by mass or more. When the ratio is equal to or more than the lower limit, the oxygen barrier properties of the multilayer film and the gas barrier layer are further improved. That is, in the gas barrier layer, the ratio of the content of resins other than the oxygen barrier resin to the content of the resin is preferably 20 mass% or less, and may be, for example, 15 mass% or less, 10 mass% or less, or 5 mass% or less. The content ratio of the oxygen barrier resin is usually the same as the ratio of the content (parts by mass) of the oxygen barrier resin to the content (parts by mass) of the resin in the composition for forming a gas barrier layer, which will be described later.

[0094] In the gas barrier layer, the ratio of the content of the oxygen barrier resin to the content of the resin is 100 mass % or less. The proportion may be, for example, any one of 85 to 100 mass %, 90 to 100 mass %, and 95 to 100 mass %.

[0095] The gas barrier layer may consist of one layer (single layer) or two or more layers. When the gas barrier layer consists of multiple layers, these multiple layers may be the same or different from one another, and the combination of these multiple layers is not particularly limited as long as it does not impair the effects of the present invention.

[0096] The thickness of the gas barrier layer is not particularly limited, but is preferably 5 μm or more, more preferably 7 μm or more. When the thickness of the gas barrier layer is equal to or greater than the lower limit, the gas barrier properties of the multilayer film and the gas barrier layer are improved. There is no particular upper limit to the thickness of the gas barrier layer, either. For example, the thickness of the gas barrier layer is preferably 60 μm or less in order to avoid excessive thickness. The thickness of the gas barrier layer may be, for example, either 5 to 60 μm or 7 to 60 μm. When the gas barrier layer is made up of multiple layers, the total thickness of these multiple layers preferably falls within the above-mentioned numerical range.

[0097] <Impact-resistant layer> The multilayer film may further include an impact-resistant layer (impact-resistant layer 15 in the multilayer film 1 shown in FIG. 1) on the surface of the gas barrier layer opposite to the tear-resistant layer side. The impact-resistant layer imparts impact resistance (shape retention) to the multilayer film. The impact resistant layer is preferably transparent. The impact-resistant layer is preferably a resin layer containing a resin.

[0098] Preferred examples of the resin contained in the impact-resistant layer include polyolefins such as low-density polyethylene (LDPE), high-density polyethylene (HDPE), and polypropylene (PP); polyamides; polyesters such as polyethylene terephthalate (PET); vinyl resins; and cellulose (including cellophane and paper). These resins are suitable as resins that exhibit impact resistance (sometimes referred to as "high-impact resins" in this specification).

[0099] The polyamide contained in the impact-resistant layer may be, for example, the same polyamide as that contained in the tear-resistant layer. Examples of the vinyl resin contained in the impact-resistant layer include the same vinyl resin as that contained in the gas barrier layer.

[0100] The impact-resistant layer may contain only one type of resin or two or more types, and when two or more types are contained, the combination and ratio thereof can be selected arbitrarily depending on the purpose. For example, the impact-resistant layer may contain one or two or more types of the high-impact resin and no resin other than the high-impact resin, or may contain one or two or more types of resin other than the high-impact resin and no high-impact resin, or may contain one or two or more types of the high-impact resin and one or two or more types of resin other than the high-impact resin.

[0101] The resin contained in the impact-resistant layer is preferably polyamide.

[0102] The impact-resistant layer may contain only the resin (i.e., it may be a layer made of the resin), or it may contain both the resin and other components (in other words, non-resin components) (i.e., it may be a layer made of the resin and other components).

[0103] Examples of the other components (non-resin components) contained in the impact-resistant layer include additives known in the art. Examples of the additives include the same additives as those contained in the base layer.

[0104] The impact-resistant layer may contain only one type of other component, or two or more types. When two or more types are contained, the combination and ratio thereof can be selected arbitrarily depending on the purpose.

[0105] In the impact-resistant layer, the content of the resin relative to the total mass of the impact-resistant layer is preferably 80% by mass or more, and may be, for example, 85% by mass or more, 90% by mass or more, or 95% by mass or more. When the content is equal to or more than the lower limit, the impact resistance of the multilayer film and the impact-resistant layer becomes higher. That is, in the impact-resistant layer, the content ratio of the other components (non-resin components) relative to the total mass of the impact-resistant layer is preferably 20 mass% or less, and may be, for example, 15 mass% or less, 10 mass% or less, or 5 mass% or less. The content ratio of the resin is usually the same as the ratio of the content (parts by mass) of the resin to the total content (parts by mass) of components that do not vaporize at room temperature in the composition for forming the impact-resistant layer described below.

[0106] In the impact-resistant layer, the content of the resin relative to the total mass of the impact-resistant layer is 100 mass % or less. The proportion may be, for example, any one of 85 to 100 mass %, 90 to 100 mass %, and 95 to 100 mass %.

[0107] When the impact-resistant layer contains the high-impact resin, the ratio of the high-impact resin to the total resin content in the impact-resistant layer is preferably 80% by mass or more, and may be, for example, 85% by mass or more, 90% by mass or more, or 95% by mass or more. When the ratio is equal to or greater than the lower limit, the impact resistance of the multilayer film and the impact-resistant layer becomes higher. That is, in the impact-resistant layer, the ratio of the content of resins other than the high-impact-resistant resin to the content of the resin is preferably 20% by mass or less, and may be, for example, 15% by mass or less, 10% by mass or less, or 5% by mass or less. The content ratio of the high impact resistant resin is usually the same as the ratio of the content (parts by mass) of the high impact resistant resin to the content (parts by mass) of the resin in the composition for forming the impact resistant layer described below.

[0108] In the impact-resistant layer, the ratio of the content of the high impact-resistant resin to the content of the resin is 100 mass % or less. The proportion may be, for example, any one of 85 to 100 mass %, 90 to 100 mass %, and 95 to 100 mass %.

[0109] The impact-resistant layer may be composed of one layer (single layer) or two or more layers. When the impact-resistant layer is composed of multiple layers, these multiple layers may be the same or different from each other, and the combination of these multiple layers is not particularly limited as long as it does not impair the effects of the present invention.

[0110] The thickness of the impact-resistant layer is not particularly limited, but is preferably 5 μm or more, more preferably 10 μm or more. When the thickness of the impact-resistant layer is equal to or greater than the lower limit, the impact resistance of the multilayer film and the impact-resistant layer becomes higher. There is no particular upper limit to the thickness of the impact-resistant layer, either. For example, the thickness of the impact-resistant layer is preferably 300 μm or less in order to avoid excessive thickness. The thickness of the impact-resistant layer may be, for example, either 5 to 300 μm or 10 to 300 μm. When the impact-resistant layer is made up of a plurality of layers, it is preferable that the total thickness of these layers is within the above-mentioned numerical range.

[0111] <Adhesive layer> The multilayer film may further include an adhesive layer (for example, adhesive layer 16 in the multilayer film 1 shown in FIG. 1) between two adjacent layers that constitute the multilayer film. When the multilayer film includes the adhesive layer, it is preferable that the adhesive layer is provided between the base layer and the tear-resistant layer. The adhesive layer is preferably transparent. The adhesive layer includes an adhesive.

[0112] The adhesive contained in the adhesive layer is not particularly limited as long as it can bond two layers to be bonded together with sufficient strength. The adhesive may be, for example, an adhesive resin such as an olefin-based resin (that is, a polymer of one or more olefin monomers).

[0113] More specific examples of the olefin-based resin contained in the adhesive layer include ethylene-based copolymers, propylene-based copolymers, and butene-based copolymers. The ethylene copolymer is a copolymer of ethylene and a monomer other than ethylene. The propylene copolymer is a copolymer of propylene and a monomer other than propylene. The butene copolymer is a copolymer of butene and a monomer other than butene.

[0114] Examples of the ethylene copolymer contained in the adhesive layer include copolymers of ethylene and vinyl group-containing monomers. Examples of copolymers of ethylene and vinyl group-containing monomers include maleic anhydride-grafted linear low-density polyethylene, ethylene-vinyl acetate copolymer (EVA), ethylene-methyl acrylate copolymer (EMA), ethylene-methyl methacrylate copolymer (EMMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-acrylic acid copolymer (EAA), ethylene-methacrylic acid copolymer (EMAA), ethylene-ethyl acrylate-maleic anhydride copolymer (E-EA-MAH), ionomer (ION), and ethylene-based thermoplastic elastomer. The ionomer contained in the adhesive layer may be, for example, the same as the ionomer contained in the sealant layer.

[0115] The propylene copolymer contained in the adhesive layer may be, for example, a copolymer of propylene and a vinyl group-containing monomer. Examples of copolymers of propylene and vinyl group-containing monomers include maleic anhydride graft-modified linear low-density polypropylene and propylene-based thermoplastic elastomers.

[0116] Examples of the butene copolymer contained in the adhesive layer include a copolymer of 1-butene and a vinyl group-containing monomer, a copolymer of 2-butene and a vinyl group-containing monomer, and modified products of these copolymers (modified copolymers).

[0117] The adhesive layer may contain only one type of adhesive, or two or more types. When two or more types are contained, the combination and ratio thereof can be selected arbitrarily depending on the purpose.

[0118] The adhesive layer may contain only an adhesive (i.e., it may be a layer made of an adhesive), or it may contain both an adhesive and other components (i.e., it may be a layer made of an adhesive and other components).

[0119] The other components contained in the adhesive layer may be either resin components (sometimes referred to in this specification as "other resin components") or non-resin components (sometimes referred to in this specification as "other non-resin components").

[0120] The other resin component contained in the adhesive layer is not particularly limited as long as it is a resin other than an adhesive.

[0121] Examples of the other non-resin components contained in the adhesive layer include additives known in the art. Examples of the additives include the same additives as those contained in the base layer.

[0122] The adhesive layer may contain only one type of other component, or two or more types. When there are two or more types, the combination and ratio thereof can be selected arbitrarily depending on the purpose.

[0123] In the adhesive layer, the proportion of the adhesive content relative to the total mass of the adhesive layer is preferably 90% by mass or more, and may be, for example, 95% by mass or more, 97% by mass or more, or 99% by mass or more. When this proportion is equal to or greater than the lower limit, the adhesive strength of the adhesive layer becomes greater. The upper limit of the proportion is 100% by mass. The ratio is usually the same as the ratio of the content (parts by mass) of the adhesive to the total content (parts by mass) of components that do not vaporize at room temperature in the adhesive layer-forming composition described below.

[0124] The adhesive layer may consist of one layer (single layer) or two or more layers. When the adhesive layer consists of multiple layers, these multiple layers may be the same or different from each other, and the combination of these multiple layers is not particularly limited as long as it does not impair the effects of the present invention.

[0125] The thickness of the adhesive layer is not particularly limited, but is preferably 5 to 80 μm, more preferably 10 to 75 μm, and even more preferably 15 to 70 μm. When the thickness of the adhesive layer is equal to or greater than the lower limit, the adhesive strength of the adhesive layer is increased. When the thickness of the adhesive layer is equal to or less than the upper limit, the adhesive layer is prevented from becoming excessively thick. When the adhesive layer is made up of multiple layers, the total thickness of these multiple layers preferably falls within the above-mentioned numerical range.

[0126] The thickness of the multilayer film is not particularly limited, but is preferably 60 to 350 μm, and may be, for example, 80 to 320 μm. When the thickness of the multilayer film is equal to or greater than the lower limit, the mechanical strength of the multilayer film is increased. When the thickness of the multilayer film is equal to or less than the upper limit, the flexibility of the multilayer film is increased. The thickness of the multilayer film means the total thickness of all layers constituting the multilayer film, and in the case of the multilayer film 1 shown in Figure 1, it means the total thickness of the sealant layer 11, base layer 12, adhesive layer 16, tear-resistant layer 13, gas barrier layer 14 and impact-resistant layer 15.

[0127] The multilayer film is preferably transparent.

[0128] The haze of the multilayer film is preferably more than 10% and not more than 20%, more preferably 10.1 to 18%, and may be, for example, 10.1 to 16%. In this specification, unless otherwise specified, the "haze of a multilayer film" means the haze measured from the outside of the multilayer film on the side opposite to the sealant layer side (in the case of the multilayer film 1 shown in Figure 1, on the side of the impact-resistant layer 15). When the haze of the multilayer film is equal to or greater than the lower limit, adhesion of components such as oil from the stored items (e.g., oil stains) to the base material made using the multilayer film in a package described below is less noticeable, improving visibility of the stored items and providing more preferable properties for the package. When the haze of the multilayer film is equal to or less than the upper limit, the transparency of the multilayer film is increased, and in a package described below, the transparency of the base material made using the multilayer film is also increased, improving visibility of the stored items and providing more preferable properties for the package.

[0129] In this specification, the term "haze" refers to a value measured in accordance with JIS K 7136:2000.

[0130] <<Multilayer film manufacturing method>> The multilayer film can be produced, for example, by a feed block method in which resins or resin compositions, etc., which are materials for forming each layer, are melt-extruded using several extruders; a coextrusion T-die method such as a multi-manifold method; or an air-cooled or water-cooled coextrusion inflation method.

[0131] The multilayer film can also be produced by separately preparing two or more films for constituting any two or more of the layers in advance, laminating them together using a thermal lamination method or the like without using an adhesive, and further laminating other layers as needed to achieve the desired arrangement.

[0132] The resin composition used to form any layer in the multilayer film may be produced by adjusting the types and contents of the components contained therein so that the layer to be formed contains the desired components in the desired amounts. For example, the ratio of the contents of the components that do not vaporize at room temperature in the resin composition is usually the same as the ratio of the contents of the components in the layer formed from this resin composition.

[0133] Examples of resin compositions (sometimes referred to herein as "compositions for forming a base layer") for forming a base layer (base layer 12 in the multilayer film 1 shown in FIG. 1) include those containing polyethylene with a melting point of 120°C or higher and, if necessary, other components. The other components are the components described above.

[0134] Resin compositions (sometimes referred to herein as "sealant layer-forming compositions") for forming a sealant layer (sealant layer 11 in the multilayer film 1 shown in FIG. 1) include, for example, compositions containing a polypropylene resin, a polyethylene resin, and, if necessary, other components. The other components are the components described above.

[0135] The resin composition (sometimes referred to herein as "tear-resistant layer-forming composition") for forming the tear-resistant layer (tear-resistant layer 13 in the multilayer film 1 shown in FIG. 1) may contain, for example, the resin described above and, if necessary, other components, and preferably contains the polyamide described above and, if necessary, the other components. The other components are the components described above.

[0136] The resin composition (sometimes referred to herein as "gas barrier layer-forming composition") for forming the gas barrier layer (gas barrier layer 14 in the multilayer film 1 shown in FIG. 1) may, for example, be one containing the resin described above and, if necessary, other components, and is preferably one containing the oxygen barrier resin and, if necessary, the other components. The other components are the components described above.

[0137] The resin composition (sometimes referred to herein as "composition for forming impact-resistant layer") for forming the impact-resistant layer (impact-resistant layer 15 in the multilayer film 1 shown in FIG. 1) may, for example, be one containing the resin described above and, if necessary, other components, and preferably one containing the high-impact-resistant resin and, if necessary, the other components. The other components are the components described above.

[0138] Resin compositions (sometimes referred to herein as "adhesive layer-forming compositions") for forming adhesive layers (for example, adhesive layer 16 in the multilayer film 1 shown in FIG. 1) include those containing the adhesive and, if necessary, other components. The other components are the components described above.

[0139] <<Packaging>> The multilayer film is suitable as a constituent material for packaging, and is particularly suitable as a base material for gas-exchange packaging or vacuum packaging. The gas-substituted packaging body is a packaging body obtained by using a base material with a storage section for storing the packaged item (in other words, the stored item), storing the item in the storage section, filling the storage section with an inert gas, and sealing (sealing) the base material with a lid material in this state. The vacuum package is a package obtained by using the base material, storing items in the storage section, evacuating the storage section, and then sealing the base material with a lid material in this state.

[0140] That is, the packaging body of this embodiment includes one equipped with the multilayer film. A preferred example of the packaging body of this embodiment is a packaging body that includes a lid material and a base material, the base material being made of the multilayer film, and the sealant layer in the multilayer film being positioned on the lid material side.

[0141] FIG. 2 is a cross-sectional view schematically illustrating an example of a package according to one embodiment of the present invention. The package 101 shown here comprises a cover material 8 and a base material 10. The base material 10 is made of the multilayer film 1 shown in Fig. 1. The base material 10 may be, for example, a deep-drawn product of the multilayer film 1. That is, the packaging body 101 may be a deep-drawn packaging body. The lid member 8 is formed using, for example, the multilayer film 1 or other multilayer films that do not fall under the category of the multilayer film of this embodiment. In addition, in the base material 10 in FIG. 2, the distinction between the layers of the multilayer film 1 that constitutes it is omitted.

[0142] The base material 10 has a recess 100 formed therein. One surface 10b of the base material 10 excluding the recess 100 (sometimes referred to as the "second surface" in this specification) and one surface 8b of the lid material 8 (sometimes referred to as the "second surface" in this specification) are both sealing surfaces and face each other. That is, in the package 101, the sealant layer 11 in the multilayer film 1 (in other words, the base material 10) is disposed on the lid material 8 side.

[0143] The package 101 is formed by sealing the lid material 8 and the base material 10. More specifically, the second surface 10b of the base material 10 in the area excluding the recessed portion 100 and the second surface 8b of the lid material 8 are overlapped and sealed to each other in the area near their peripheral edges. As a result, in the area of ​​the recessed portion 100 of the base material 10, a storage section 101a is formed between the second surface 10b of the base material 10 and the second surface 8b of the lid material 8. The item 9 is stored in this storage section 101a.

[0144] The second surface 10b of the base material 10 is the same as the other surface 11b of the sealant layer 11 in the multilayer film 1. The other surface 10a (sometimes referred to as the "first surface" in this specification) of the base material 10 is the same as the one surface 15a of the impact-resistant layer 15 in the multilayer film 1.

[0145] The lid material 8 can be appropriately selected depending on the use of the package 101. The lid material 8 may be made of a single-layer or multi-layer resin film that can be used in ordinary packaging (for example, deep-draw packaging). The lid member 8 is preferably transparent.

[0146] The thickness of the lid material 8 may be, for example, 30 to 150 μm.

[0147] In Figure 2, some gaps can be seen between the stored item 9 and the base material 10, and between the stored item 9 and the lid material 8 within the storage section 101a of the packaging body 101, but the presence of these gaps is not essential for the packaging body 101 when the stored item 9 is stored therein.

[0148] The thickness of the base material 10 at its flat portion may be the same as the thickness of the multilayer film 1 described above.

[0149] The package 101, which is configured by filling the storage section 101a with an inert gas, is a gas-flux package. Examples of the inert gas include nitrogen gas. The package 101, in which the storage section 101a is vacuum-evacuated, is a vacuum package.

[0150] So far, the packaging body has been described as having a lid material obtained using the multilayer film 1 shown in Figure 1, but the lid material in the packaging body is not particularly limited as long as it is obtained using the multilayer film of the present embodiment described above.

[0151] In the packaging body of this embodiment, the peel strength between the lid material and the base material (in the packaging body 101 shown in FIG. 2, the peel strength between the lid material 8 and the base material 10) is preferably 5 to 15 N / 15 mm. When the peel strength is equal to or greater than the lower limit, unintended peeling between the lid material and the base material in the packaging body is suppressed, and the packaged state of the contents can be maintained more stably. When the peel strength is equal to or less than the upper limit, intended peeling between the lid material and the base material in the packaging body becomes easier, and easy-peel properties are improved.

[0152] In this specification, unless otherwise specified, the peel strength between the lid material and the base material in a package refers to a measured value obtained by measurement in accordance with JIS Z 0238:1998.

[0153] When a plurality of packages (e.g., 25 to 35 packages) of this embodiment, manufactured using the same lid and base materials and by the same method, are used and the peel strength between the lid and base material is measured for each package, and the difference between the maximum and minimum peel strengths is determined, the difference can be set to 7 N / 15 mm or less (0 to 7 N / 15 mm). By using the multilayer film, the package of this embodiment reduces variations in peel strength between the lid and base material, and has stable easy-peel properties, even if the base material does not contain a highly rigid resin such as PET.

[0154] The rate of change in the thickness of the sealant layer in the multilayer film (base material) before and after the production of the package of this embodiment is an index of the degree of variation in the peel strength between the lid material and the base material. More specifically, for example, it is as follows. A laminated film having a linear low-density polyethylene layer (e.g., 40 μm thick) as a sealant layer is used, and the sealant layer in the laminated film and the sealant layer in the multilayer film are heat-sealed under conditions of a sealing temperature of 150°C, a sealing time of 2 seconds, and a sealing pressure of 0.5 MPa to produce a sealed body. Next, the minimum and maximum thicknesses of the sealant layer in the multilayer film after this heat sealing (after the production of the sealed body) are determined. Next, the ratio of the thickness of the sealant layer in the multilayer film after heat sealing to the thickness of the sealant layer in the multilayer film before heat sealing (before the sealed body is produced) (sometimes referred to in this specification as the "variation ratio of the sealant layer thickness") is calculated using the following formula. [Variation rate of sealant layer thickness (%)] = [Sealant layer thickness after heat sealing (μm)] / [Sealant layer thickness before heat sealing (μm)] × 100 At this time, the minimum and maximum values ​​are used as the thickness values ​​of the sealant layer in the multilayer film after heat sealing, and the minimum and maximum values ​​of the fluctuation rate (fluctuation rate of the sealant layer thickness) are calculated. More specifically, the minimum and maximum values ​​of the fluctuation rate are calculated using the following formula: [Minimum fluctuation rate of sealant layer thickness (%)] = [Minimum sealant layer thickness after heat sealing (μm)] / [Sealant layer thickness before heat sealing (μm)] × 100 [Maximum value of sealant layer thickness fluctuation rate (%)] = [Maximum value of sealant layer thickness after heat sealing (μm)] / [Sealant layer thickness before heat sealing (μm)] × 100 The minimum and maximum values ​​of the variation rate of the thickness of the sealant layer thus obtained can be used as indicators of the degree of variation in the peel strength between the cover material and the base material.

[0155] In this embodiment, the minimum value of the variation rate of the thickness of the sealant layer is preferably 60% or more, more preferably 65% ​​or more, and may be, for example, 70% or more. In the package having the minimum value of the variation rate equal to or greater than the lower limit, the variation in peel strength between the lid material and the base material is highly suppressed, making it easier to open. On the other hand, the maximum value of the fluctuation rate is preferably 140% or less, more preferably 135% or less, and even more preferably 130% or less. In the package in which the maximum value of the fluctuation rate is equal to or less than the upper limit, the variation in peel strength between the lid material and the base material is highly suppressed, and opening is easier. In this embodiment, for example, the minimum value of the fluctuation rate may be 60% or more and the maximum value of the fluctuation rate may be 140% or less, or the minimum value of the fluctuation rate may be 65% or more and the maximum value of the fluctuation rate may be 135% or less, or the minimum value of the fluctuation rate may be 70% or more and the maximum value of the fluctuation rate may be 130% or less.

[0156] When a plurality of packages (e.g., 25 to 35 packages) of this embodiment, manufactured using the same lid and base materials and the same method, are used, the variation rate of the sealant layer thickness is calculated for each package, and the difference between the maximum and minimum values ​​of the variation rate is determined for each package, the difference can be kept to 48% or less (0 to 48%). In the package of this embodiment, variation in peel strength between the lid and base materials is suppressed, and therefore the difference is also suppressed to a low level.

[0157] <<Packaging manufacturing method>> The packaging body of this embodiment can be manufactured, for example, by molding the multilayer film to create a base material with a recess, storing the item to be packaged in the recess in the base material, overlapping the lid material and the base material to form the storage section, and heat-sealing the lid material and the base material while filling the recess with an inert gas or while reducing the pressure inside the recess (vacuum degassing).

[0158] The heating temperature (forming temperature) during forming of the multilayer film is preferably 80 to 130°C. The heating time and molding time during molding of the multilayer film are preferably 1 to 3 seconds.

[0159] The heating temperature (sealing temperature) during the heat sealing is preferably 130 to 160°C. The pressure (sealing pressure) during the heat sealing is preferably 0.2 to 0.6 MPa. The heating time (sealing time) during the heat sealing is preferably 1 to 3 seconds.

[0160] The inert gas filled into the storage section (inside the recess) during the production of the gas replacement package is as described above. During the production of the vacuum package, the pressure in the storage section (inside the recess) after decompression (vacuum degassing) is 3×10 3 It is preferably 30 mbar or less. [Example]

[0161] The present invention will be described in more detail below with reference to specific examples, although the present invention is not limited to the examples shown below.

[0162] [Example 1] <<Manufacturing of multilayer films>> The resin constituting the sealant layer was low-density polyethylene (LDPE) (UBE Polyethylene (registered trademark) F324C manufactured by Ube Maruzen Polyethylene Co., Ltd., density 0.924 g / cm 3 LDPE (1), melting point 112°C, sometimes referred to as "LDPE (1)" in this specification), homopolypropylene (hPP) (Prime Polypro Y400GP manufactured by Prime Polymer Co., Ltd., density 0.905 g / cm 3 A polyethylene-based anti-fog masterbatch ("Elecut Master L117A" manufactured by Takemoto Yushi Co., Ltd.) was prepared. The polyethylene-based anti-fog masterbatch contained low-density polyethylene (LDPE) (density 0.923 g / cm 3) as a base resin. 3 , melting point 111°C, in this specification, this LDPE may be referred to as "LDPE (2)"), and further contains an anti-fogging agent. The resin constituting the base layer was high-density polyethylene (HDPE) (Prime Polymer "Hi-Zex 3300F", density 0.950 g / cm 3 A HDPE having a melting point of 130°C, which may be referred to as "HDPE(1)" in this specification, was prepared. The resin constituting the adhesive layer was acid-modified polyethylene (acid-modified PE, adhesive resin, Mitsui Chemicals "Admer (registered trademark) NF536", density 0.905 g / cm 3 , melting point 120°C) was prepared. The resin used to form the tear-resistant layer and impact-resistant layer was nylon (Ny) (Ube Industries, Ltd. "Ube Nylon 1030B2", density 1.14 g / cm 3 , melting point 225°C) was prepared. The resin constituting the gas barrier layer was ethylene-vinyl alcohol copolymer (EVOH) ("EVAL (registered trademark) J171B" manufactured by Kuraray Co., Ltd., ethylene content 32 mol%, density: 1.18 g / cm3 , melting point 183°C) was prepared.

[0163] A sealant layer-forming composition was produced by mixing the LDPE (1), the hPP, and the polyethylene-based anti-fog masterbatch. In the sealant layer-forming composition, the proportions of the LDPE (1), the hPP, the LDPE (2), and the anti-fog agent were 76 mass%, 15 mass%, 8 mass%, and 1 mass%, respectively, relative to the total content (parts by mass) of components that do not vaporize at room temperature.

[0164] A multilayer film having the structure shown in FIG. 1 was produced according to the following procedure. That is, the sealant layer-forming composition, the HDPE (1), the acid-modified PE, the Ny, the EVOH, and the Ny were co-extruded in this order to obtain a multilayer film (thickness 200 μm) composed of a sealant layer (thickness 14 μm), a base layer (thickness 52 μm), an adhesive layer (thickness 44 μm), a tear-resistant layer (thickness 42 μm), a gas barrier layer (thickness 16 μm), and an impact-resistant layer (thickness 32 μm) laminated in this order in the thickness direction.

[0165] <<Evaluation of multilayer films>> <Measurement of the melt flow rate at 190°C of the polyethylene contained in the base layer> The melt flow rate (MFR) of the HDPE (1) at 190°C was measured in accordance with JIS K 7210. The results are shown in the "MFR (190°C)" column in Table 1.

[0166] <Measurement of haze of multilayer film> The haze of the multilayer film obtained above was measured from the outside of the impact-resistant layer side in accordance with JIS K 7136: 2000. The results are shown in Table 1.

[0167] <<Packaging Manufacturing>> <Production of lid materials> Linear low-density polyethylene (LLDPE) (Ultzex ​​2022L manufactured by Prime Polymer Co., Ltd.) was used to prepare an LLDPE film (thickness: 40 μm) by the T-die extrusion method. A laminated film for lid material was produced by dry laminating a biaxially oriented polypropylene film (OPP film, thickness 20 μm), a biaxially oriented polyethylene terephthalate film with aluminum vapor deposition (VM-PET film, thickness 12 μm), and the LLDPE film (thickness 40 μm) obtained above.

[0168] <Manufacture of soles> The multilayer film obtained above was deep-drawn using a deep-draw molding machine ("R-535" manufactured by Multivac) under conditions of a heating temperature of 100°C, a heating time of 2 seconds, and a forming time of 2 seconds to form a recess, thereby producing a base material for a package. The obtained base material measured 120 mm x 150 mm, and the recess depth was 30 mm.

[0169] <Packaging production> A processed meat product (200 g of sausage) was placed in the recess of the base material obtained above, and the LLDPE layer of the lid material (laminated film) obtained above was placed opposite the sealant layer of the base material (multilayer film), sandwiching the processed meat product between the lid material and the base material. The interior of the storage space formed by the lid material and base material was vacuum degassed at a temperature of 150°C for 2 seconds. Next, the peripheral edges of the lid material and base material were heat-sealed at a sealing temperature of 150°C, a sealing time of 2 seconds, and a sealing pressure of 0.5 MPa, thereby producing a package (vacuum package, deep-draw package). Finally, the pressure in the storage space (inside the recess) was 1.5 x 10 3 The pressure was set to 15 mbar.

[0170] <<Packaging evaluation>> <Calculation of the variation rate of the sealant layer thickness in the base material> For the 30 packages obtained above, the thickness of the sealant layer in the base material was measured using a polarizing microscope, and the minimum and maximum values ​​were determined for each package. Then, using the formula described above, the variation rate of the sealant layer thickness was calculated for each package, and the minimum and maximum values ​​were determined. In this example, the "thickness of the sealant layer before heat sealing" in the formula was 14 μm. The range of calculated values ​​for the 30 packages is shown in Table 1. In this example, the smallest variation rate was 80%, and the largest variation rate was 120%.

[0171] <Measurement of peel strength of sealed part> The peel strength of the seal portions of the 30 packages obtained above (peel strength between the lid material and the base material, N / 15 mm) was measured in accordance with JIS Z 0238: 1998. The range of the measured values ​​is shown in Table 1.

[0172] <Evaluation of visibility of stored items> Separately from the measurement of the peel strength of the seal, 10 monitors visually inspected the contents (processed meat products) in the storage compartment of each of the 10 packages obtained above, one for each package, from the base side. The monitors then evaluated the visibility of the contents using a binary choice of "good" or "bad," and based on the evaluation results, the visibility of the contents was evaluated according to the following criteria. The results are shown in Table 1. (Evaluation criteria) A: 6 to 10 monitors judged the visibility to be good. B: 6 to 10 monitors judged the visibility to be poor.

[0173] <Evaluation of peelability of lid material> After the evaluation of the visibility of the contents, one of the 10 monitors peeled off the lid of one package. The hardness was then evaluated as either "moderate" or "hard." Based on the evaluation results, the peeling feel was evaluated according to the following criteria. The results are shown in Table 1. (Evaluation criteria) A: 6 to 10 monitors judged the firmness at the time of peeling to be appropriate. B: 6 to 10 monitors judged the hardness at the time of peeling to be hard.

[0174] <<Manufacturing and evaluation of multilayer films, and manufacturing and evaluation of packaging materials>> [Example 2] Instead of HDPE (1), high-density polyethylene (HDPE) (Prime Polymer Co., Ltd. "Hi-Zex 2100J", density 0.952 g / cm) was used as the resin constituting the base layer. 3 A multilayer film was produced and evaluated, and a package was produced and evaluated in the same manner as in Example 1, except that HDPE (HPE) having a melting point of 129°C and sometimes referred to as "HDPE (2)" in this specification was used. The results are shown in Table 1.

[0175] [Examples 3 to 5] Multilayer films were produced and evaluated, and packages were produced and evaluated in the same manner as in Example 1, except that the thickness of each layer was changed as shown in Table 1 by changing the co-extrusion conditions during production of the multilayer film. The results are shown in Table 1.

[0176] [Comparative Example 1] Instead of HDPE (1), high-density polyethylene (HDPE) (Prime Polymer "Hi-Zex 7000F", density 0.951 g / cm) was used as the resin constituting the base layer. 3 A multilayer film was produced and evaluated, and a package was produced and evaluated in the same manner as in Example 1, except that HDPE (HPE (3)) having a melting point of 129°C and sometimes referred to as "HDPE (3)" was used. The results are shown in Table 2.

[0177] Comparative Example 2 Instead of HDPE (1), high-density polyethylene (HDPE) (Prime Polymer Co., Ltd. "Hi-Zex 2100JH", density 0.951 g / cm) was used as the resin constituting the base layer. 3A multilayer film was produced and evaluated, and a package was produced and evaluated in the same manner as in Example 1, except that HDPE (HPE (4)) with a melting point of 129°C (sometimes referred to as "HDPE (4)" in this specification) was used. The results are shown in Table 2.

[0178] Comparative Example 3 Instead of HDPE (1), low-density polyethylene (LDPE) (F222NH manufactured by Ube Maruzen Polyethylene Co., Ltd., density 0.922 g / cm ) was used as the resin constituting the base layer. 3 A multilayer film was produced and evaluated, and a package was produced and evaluated in the same manner as in Example 1, except that LDPE (1,000 sq ft, melting point 110°C; in this specification, this LDPE may be referred to as "LDPE (3)") was used. The results are shown in Table 2.

[0179] [Table 1]

[0180] [Table 2]

[0181] As is clear from the above results, in Examples 1 to 5, the difference in peel strength of the sealed portion of the package for each Example was within the range of 4 to 6 N / 15 mm, and the variation in peel strength was suppressed. Furthermore, across all Examples, the peel strength of the sealed portion of the package was 5 to 14 N / 15 mm, which was within a reasonable range. Thus, in Examples 1 to 5, even though the base material did not contain a highly rigid resin such as PET, the variation in peel strength was suppressed when the vacuum package was opened.

[0182] In Examples 1 to 5, the difference in the variation rate of the sealant layer thickness for each Example was within the range of 40 to 45%, and variation was suppressed. Furthermore, across all Examples, the variation rate of the sealant layer thickness was 65 to 130% (the minimum value of the variation rate was 65% or more, and the maximum value of the variation rate was 130% or less), which was within a reasonable range. This was consistent with the suppression of variation in peel strength, as described above.

[0183] Furthermore, in Examples 1 to 5, the hardness of the lid material when peeled off was appropriate, and the lid material felt good when peeled off. Furthermore, in Examples 1 to 5, the haze of the multilayer films was 10.5 to 14.4%, which was within a suitable range, and as a result, the visibility of the contents of the package was good.

[0184] In Examples 1 to 5, the melting point of the polyethylene contained in the base layer was 129 to 130°C, the content of polyethylene in the base layer relative to the total mass of the base layer was 100 mass%, and the MFR of the polyethylene at 190°C was 1.1 to 5.7 g / 10 min. In addition, in the sealant layers of Examples 1 to 5, the proportion of the polypropylene resin content relative to the total mass of the sealant layer was 15 mass %.

[0185] In Examples 1 to 5, the density of the polyethylene was 0.950 to 0.952 g / cm 3 The thickness of the base layer was 26 to 78 μm, the ratio of [base layer thickness]:[sealant layer thickness] was 79:21, and the thickness of the multilayer film was 100 to 300 μm.

[0186] In contrast, in Comparative Example 1, the haze of the multilayer film was 20.4%, the base material was cloudy, the visibility of the contents was poor, and it was unsuitable as a package. In Comparative Example 1, the MFR of the polyethylene contained in the base layer at 190° C. was 0.041 g / 10 min, which was too small.

[0187] In Comparative Example 2, the peel strength of the sealed portion of the package was 9-18 N / 15 mm, with localized increases, resulting in a large difference in peel strength of 9 N / 15 mm. Furthermore, the variation rate of the sealant layer thickness was 95-145%, with a difference of 50%, both of which were large. Furthermore, the lid was stiff when peeled, resulting in a poor peeling feel. Furthermore, in Comparative Example 2, the haze of the multilayer film was 9.8%, which was too small, so that oil adhesion (oil stains) from the stored items was noticeable on the base material, making the visibility of the stored items poor and making it unsuitable as packaging. In Comparative Example 2, the MFR of the polyethylene contained in the base layer at 190° C. was 9.1 g / 10 min, which was too large.

[0188] Comparative Example 3 showed similar trends to Comparative Example 2. That is, in Comparative Example 3, the peel strength of the sealed portion of the package was 9 to 20 N / 15 mm, and was locally high, with a large difference in peel strength of 11 N / 15 mm. Furthermore, the variation rate of the sealant layer thickness was 95 to 150%, and the difference in the variation rate was 55%, both of which were large. Furthermore, the lid was stiff when peeled, and the peeling feel of the lid was poor. In Comparative Example 3, the haze of the multilayer film was 8.2%, which was too small, so that oil adhesion (oil stains) from the stored items was noticeable on the base material, making the stored items difficult to see, and the film was unsuitable as a package. In Comparative Example 3, the melting point of the polyethylene contained in the base layer was 110°C, which was low. [Industrial Applicability]

[0189] INDUSTRIAL APPLICABILITY The present invention can be used as a gas-substituted package or a vacuum-packaged package that exhibits stable easy-peel properties when opened. [Explanation of symbols]

[0190] 1. Multilayer film 11: sealant layer, 11a: one surface of the sealant layer 12...Base material layer 13. Tear-resistant layer 14. Gas barrier layer 15. Impact-resistant layer 16...adhesive layer 101...Packaging 8...Lid material 9. Storage items 10...Bottom material

Claims

1. A multilayer film, the multilayer film comprises a sealant layer, a base layer provided on one surface of the sealant layer, and an impact-resistant layer provided on a surface of the base layer opposite to the sealant layer side, the base layer being in direct contact with the sealant layer; the multilayer film further includes a gas barrier layer between the base layer and the impact-resistant layer, the base material layer contains polyethylene having a melting point of 120°C or higher, and the content of the polyethylene in the base material layer is 50% by mass or higher relative to the total mass of the base material layer; the polyethylene has a melt flow rate at 190°C of 0.5 to 7 g / 10 min, as measured in accordance with JIS K 7210; the sealant layer contains a polypropylene-based resin and a polyethylene-based resin, and the content of the polypropylene-based resin in the sealant layer is 5 to 40% by mass relative to the total mass of the sealant layer; the impact-resistant layer contains polyamide, and the content of the polyamide in the impact-resistant layer is 80% by mass or more relative to the total mass of the impact-resistant layer; a multilayer film, wherein the gas barrier layer comprises an ethylene-vinyl alcohol copolymer, and in the ethylene-vinyl alcohol copolymer, the proportion of structural units derived from ethylene relative to the total amount of structural units is 25 to 40 mol %.

2. The density of the polyethylene is 0.925 to 0.970 g / cm ３ 2. The multilayer film of claim 1, wherein

3. 3. The multilayer film according to claim 1, wherein the thickness of the substrate layer is 5 to 125 μm.

4. The multilayer film according to any one of claims 1 to 3, wherein the ratio of the thickness of the substrate layer to the thickness of the sealant layer is 80:20 to 20:

80.

5. The multilayer film according to any one of claims 1 to 4, wherein the thickness of the multilayer film is 60 to 350 µm.

6. The multilayer film according to any one of claims 1 to 5, wherein the haze of the multilayer film is more than 10% and not more than 20%.

7. 7. The multilayer film according to claim 1, wherein the multilayer film is a laminate film having a linear low-density polyethylene layer as a sealant layer, and the sealant layer in the laminate film and the sealant layer in the multilayer film are heat-sealed under conditions of a sealing temperature of 150°C, a sealing time of 2 seconds, and a sealing pressure of 0.5 MPa, and the minimum and maximum values ​​of the thickness of the sealant layer in the multilayer film after the heat-sealing are determined. The minimum and maximum values ​​are used to determine the minimum and maximum values ​​of the ratio of the thickness of the sealant layer in the multilayer film after the heat-sealing to the thickness of the sealant layer in the multilayer film before the heat-sealing, and the minimum and maximum values ​​of the ratio are found to be 60% or more and 140% or less.

8. It has a lid material and a base material, The base material is a multilayer film according to any one of claims 1 to 7, A package, wherein the sealant layer in the multilayer film is disposed on the lid material side.

9. 9. The package according to claim 8, wherein the peel strength between the lid material and the base material is 5 to 15 N / 15 mm.

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