Multilayer film and packaging

Abstract

To provide a multilayer film which can produce a skin pack packaging body, has oxygen barrier properties, has high followability to an object to be stored when configuring a package and suppresses damage caused by contact with an object to be stored and to provide a package with the multilayer film.SOLUTION: There is provided a multilayer film 1 formed by laminating a sealant layer 11, a following layer 12 and a gas barrier layer 13 in this order in the thickness direction, wherein the following layer 12 contains an ionomer, the melt strength of the ionomer at a temperature of 180°C is 100 to 500 mN, the ratio of a thickness T13 of the gas barrier layer 13 to a thickness T1 of the multilayer film is 2 to 25% and the oxygen permeation amount of the multilayer film 1 under conditions at a temperature of 23°C and a relative humidity of 60% is 100 cc / (m2 day atm)) or less, as measured according to JIS K 7126-2:2006.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Among packages constructed using a film, a package in which a vacuum is drawn inside the storage compartment and the contents inside the storage compartment are sealed with the film is called a skin pack package. In skin pack packages, a resin film is typically used as the film. In skin pack packages, the film, i.e., the skin pack packaging film, is transparent, allowing the contents to be easily viewed from outside the skin pack package. Furthermore, because the skin pack packaging film is soft, it can be tightly attached to the contents by drawing a vacuum inside the storage compartment (see Patent Document 1). For example, skin pack packages equipped with a hard tray are primarily used as packages for food products, as they allow the contents to be displayed upright without shifting position. Furthermore, skin pack packages are also used for pharmaceuticals and cosmetics, in addition to food products. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-222259 Summary of the Invention [Problem to be solved by the invention]

[0004] On the other hand, skin pack packaging for food, pharmaceuticals, or cosmetics must prevent deterioration of the contents (food, pharmaceuticals, cosmetics) due to oxidation. Therefore, the film constituting the skin pack packaging is required to be able to suppress oxygen gas permeation, and a multilayer film with a multi-layer structure equipped with a gas barrier layer for suppressing oxygen gas permeation is usually used as the film. However, such multilayer films have a problem in that the presence of the gas barrier layer reduces their ability to conform to the contents. The conformability of a film to the contents means the film's ability to adhere to the contents without wrinkling. Furthermore, when a skin pack packaging is formed using a multilayer film equipped with a gas barrier layer, there is a problem in that it can be damaged, such as torn or perforated, by contact with hard and distorted contents such as frozen foods.

[0005] The present invention aims to provide a multilayer film that can be used to produce a skin pack packaging, has oxygen barrier properties, and when used to form a packaging body, has high conformability to the contents contained therein and is less likely to be damaged by contact with the contents, and a packaging body that includes the multilayer film. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention employs the following configuration. [1] A multilayer film, comprising a sealant layer, a follower layer, and a gas barrier layer laminated in this order in the thickness direction, the follower layer containing an ionomer, the melt strength of the ionomer at a temperature of 180°C being 100 to 500 mN, the ratio of the thickness of the gas barrier layer to the thickness of the multilayer film being 2 to 25%, and the oxygen permeability of the multilayer film measured in accordance with JIS K 7126-2:2006 under conditions of a temperature of 23°C and a relative humidity of 60% being 100 cc / (m 2 Multilayer film with a temperature of 100°C (-100°F) or less. [2] The multilayer film according to [1], wherein the ratio of the thickness of the sealant layer to the thickness of the multilayer film is 5% or more. [3] The multilayer film according to [1] or [2], wherein the ratio of the thickness of the follow-up layer to the thickness of the multilayer film is 5% or more.

[0007] [4] The multilayer film according to any one of [1] to [3], wherein the gas barrier layer contains an ethylene-vinyl alcohol copolymer. [5] The dynamic elastic modulus E' of the multilayer film at a temperature of 140°C is 1 x 10 7 ~1×10 10 The multilayer film according to any one of [1] to [4], wherein Pa is Pa. [6] A package comprising the multilayer film according to any one of [1] to [5]. [7]. The packaging body described in [6], wherein the packaging body is a skin pack packaging body. [Effects of the Invention]

[0008] According to the present invention, a multilayer film is provided that can be used to produce a skin pack packaging, has oxygen barrier properties, and when used to form a packaging body, has high conformability to the contents contained therein and is less likely to be damaged by contact with the contents, and a packaging body comprising the multilayer film. [Brief explanation of the drawings]

[0009] [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

[0010] <<Multilayer film>> A multilayer film according to one embodiment of the present invention is configured by laminating a sealant layer, a conforming layer, and a gas barrier layer in this order in the thickness direction, the conforming layer containing an ionomer, the melt strength of the ionomer at a temperature of 180°C being 100 to 500 mN, the ratio of the thickness of the gas barrier layer to the thickness of the multilayer film being 2 to 25%, and the oxygen transmission rate of the multilayer film measured in accordance with JIS K 7126-2:2006 under conditions of a temperature of 23°C and a relative humidity of 60% being 100 cc / (m 2 ·day·atm).

[0011] The multilayer film of this embodiment can be used to produce a skin pack package, and is suitable for forming a lid material in the skin pack package. The multilayer film of this embodiment has oxygen barrier properties, and when used to form a package, the package also has oxygen barrier properties. The multilayer film of this embodiment is provided with the above-mentioned conforming layer and satisfies the condition of the ratio of the thickness of the gas barrier layer to the thickness of the multilayer film, so that when a package is formed, it has high conformability to the contents and is less likely to be damaged by contact with the contents. In this specification, damage to the multilayer film and the lid material using the same, which will be described later, due to contact with the contents means damage such as tears or holes that occurs when these (the multilayer film, the lid material) come into contact with hard and distorted contents such as frozen foods.

[0012] In this specification, "skin pack" refers to packaging in which the contents are placed on cardboard, corrugated board, bottom film, tray, etc., and then a heated film is placed over it, and a vacuum is drawn in a chamber so that the film adheres tightly to the contents. The name "skin pack" comes from the feature that the film adheres tightly to the product body, conforming to the shape of the product, just like skin.

[0013] 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.

[0014] 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 is constructed by laminating a sealant layer 11, a conforming layer 12, and a gas barrier layer 13 in this order in the thickness direction.

[0015] The multilayer film 1 further includes an outer layer 15 disposed on the surface of the gas barrier layer 13 opposite to the sealant layer 11 side. The multilayer film 1 further includes a pinhole-resistant layer 14 disposed between the compliant layer 12 and the gas barrier layer 13 . The multilayer film 1 further includes an adhesive layer 16 (more specifically, a first adhesive layer 161) arranged between the compliant layer 12 and the pinhole-resistant layer 14, and an adhesive layer 16 (more specifically, a second adhesive layer 162) arranged between the gas barrier layer 13 and the outer layer 15.

[0016] That is, the multilayer film 1 is constructed by laminating a sealant layer 11, a conforming layer 12, a first adhesive layer 161, a pinhole-resistant layer 14, a gas barrier layer 13, a second adhesive layer 162, and an outer layer 15 in this order in the thickness direction. In the multilayer film 1, the outer layer 15 is one outermost layer, and the sealant layer 11 is the other outermost layer.

[0017] One surface 11b of the sealant layer 11 (the surface opposite to the follow-up layer 12 side, sometimes referred to as the "second surface" in this specification) is an exposed surface. One surface 15a of the outer layer 15 (the surface opposite to the sealant layer 11 side, sometimes referred to as the "first surface" in this specification) is an exposed surface.

[0018] In the multilayer film 1, the adhesive layer 16 (first adhesive layer 161) arranged between the tracking layer 12 and the pinhole-resistant layer 14 bonds the tracking layer 12 and the pinhole-resistant layer 14 together, and the adhesive layer 16 (second adhesive layer 162) arranged between the gas barrier layer 13 and the outer layer 15 bonds the gas barrier layer 13 and the outer layer 15 together. These two adhesive layers 16 (first adhesive layer 161 and second adhesive layer 162) may be the same as or different from each other.

[0019] The following layer 12 contains an ionomer, and the melt strength of the ionomer at a temperature of 180°C is 100 to 500 mN. The thickness T of the gas barrier layer 13 relative to the thickness T1 of the multilayer film 1 13 The ratio (T 13 / T1×100) is 2 to 25%. The oxygen permeability of the multilayer film 1 measured in accordance with JIS K 7126-2:2006 under conditions of a temperature of 23°C and a relative humidity of 60% was 100 cc / (m 2 ·day·atm).

[0020] The multilayer film of this embodiment will be described in more detail below.

[0021] <Sealant layer> The sealant layer (sealant layer 11 in the multilayer film 1 shown in FIG. 1) may contain, for example, a polyethylene-based resin such as ethylene-vinyl acetate copolymer (EVA), polyethylene (PE), an ionomer, or a polyethylene-based copolymer. When the sealant layer contains a polyethylene-based resin, the multilayer film exhibits pseudo-adhesion to the adherend, improving the easy peelability. Examples of the ionomer contained in the sealant layer include the same ionomers as those listed as being contained in the follow-up layer described below.

[0022] In this specification, the term "polyethylene resin" refers to a resin having at least structural units derived from ethylene, and may have only structural units derived from ethylene, or may have structural units derived from ethylene and other structural units.

[0023] Examples of polyethylene contained in the sealant layer include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), metallocene-catalyzed linear low-density polyethylene (mLLDPE), medium-density polyethylene (MDPE), and high-density polyethylene (HDPE). Linear low-density polyethylene (LLDPE) and metallocene-catalyzed linear low-density polyethylene (mLLDPE) are both types of low-density polyethylene (LDPE).

[0024] 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.

[0025] The sealant layer preferably contains one or more materials selected from the group consisting of low-density polyethylene, high-density polyethylene, and ethylene-vinyl acetate copolymer.

[0026] The sealant layer may contain only the polyethylene-based resin (i.e., may consist of the polyethylene-based resin), or may contain the polyethylene-based resin and other components (sometimes referred to as "other components" in this specification) (i.e., may consist of the polyethylene-based resin and the other components).

[0027] The other components contained in the sealant layer are not particularly limited and can be selected arbitrarily depending on the purpose, and may be, for example, either a resin component or a non-resin component. The other component, which is a resin component, is a resin that does not fall under the category of the polyethylene-based resin. The other component, which is a resin component, may be a homopolymer, which is a polymer of one type of monomer, or a copolymer, which is a polymer of two or more types of monomers.

[0028] Examples of the other non-resin components include additives known in the art. Examples of the additives include antioxidants, antistatic agents, crystal nucleating agents, inorganic particles, viscosity reducers, thickeners, heat stabilizers, lubricants, infrared absorbers, and ultraviolet absorbers.

[0029] 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.

[0030] The content (parts by mass) of the polyethylene resin in the sealant layer relative to the total mass of the sealant layer is preferably 65 to 100 mass%, more preferably 70 to 100 mass%, and even more preferably 75 to 100 mass%, and may be, for example, 85 to 100 mass%. When the content is equal to or greater than the lower limit, the easy peel property of the sealant layer is further improved. 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.

[0031] 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.

[0032] When the sealant layer contains one or more materials selected from the group consisting of low-density polyethylene, high-density polyethylene, and ethylene-vinyl acetate copolymer, the ratio of the total content (parts by mass) of low-density polyethylene, high-density polyethylene, and ethylene-vinyl acetate copolymer in the sealant layer to the total mass of the sealant layer ([total amount (parts by mass) of low-density polyethylene, high-density polyethylene, and ethylene-vinyl acetate copolymer in the sealant layer] / [total mass (parts by mass) of sealant layer]×100) is preferably 65 to 100% by mass, more preferably 70 to 100% by mass, and even more preferably 75 to 100% by mass, and may be, for example, 85 to 100% by mass. When this ratio is equal to or greater than the lower limit, the easy-peel property of the sealant layer is further improved. This ratio is usually the same as the ratio of the total content (parts by mass) of low-density polyethylene, high-density polyethylene, and ethylene-vinyl acetate copolymer to the total content (parts by mass) of components that do not vaporize at room temperature in the sealant layer-forming composition described below.

[0033] 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 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.

[0034] In this specification, not limited to the case of a sealant layer, "multiple layers may be the same or different" 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" means "at least one of the constituent materials and thicknesses of each layer is different from each other."

[0035] The thickness of the sealant layer is not particularly limited, but is preferably 4 to 90 μm, more preferably 5 to 70 μm, and even more preferably 6 to 50 μm. When the thickness of the sealant layer is equal to or greater than the lower limit, the strength of the sealant layer is increased. When the thickness of the sealant layer is equal to or less than the upper limit, the sealant layer is prevented from becoming excessively thick, and the seal strength is increased when the multilayer film is sealed by heating. Here, the "thickness of the sealant layer" means the thickness of the entire sealant layer, and for example, the thickness of a sealant layer consisting of multiple layers means the total thickness of all layers that make up the sealant layer.

[0036] The thickness of the sealant layer (thickness T1 of the sealant layer 11 in FIG. 1) relative to the thickness of the multilayer film (thickness T1 of the multilayer film 1 in FIG. 1) 11 The ratio of (in this specification, sometimes simply referred to as "proportion of the thickness of the sealant layer") is not particularly limited, but is preferably 5% or more, more preferably 5 to 50%, and even more preferably 5 to 40%. When the ratio is equal to or greater than the lower limit, the strength of the sealant layer is increased. When the ratio is equal to or less than the upper limit, the sealant layer is prevented from becoming excessively thick.

[0037] The surface (second surface) of the sealant layer opposite to the follower layer side is the exposed surface and the sealing surface.

[0038] <Followers> The compliant layer (compliant layer 12 in the multilayer film 1 shown in FIG. 1) contains an ionomer. The conforming layer provides the multilayer film with good conformability to the contents when the multilayer film is used to form a package (for example, as a lid material).

[0039] The melt strength of the ionomer at a temperature of 180°C (sometimes referred to herein as "melt strength (180°C)") is 100 to 500 mN, and may be, for example, any one of 100 to 450 mN, 100 to 350 mN, and 100 to 250 mN, or any one of 150 to 500 mN, 250 to 500 mN, and 350 to 500 mN, or may be 150 to 450 mN. When the melt strength (180°C) is equal to or greater than the lower limit, when a package is constructed using the multilayer film (lid material), damage (holes, tears, etc.) to the multilayer film (lid material) due to contact with the contents is suppressed. When the melt strength (180°C) is equal to or less than the upper limit, the following layer spreads well in the multilayer film, and the following layer can be stably formed on the sealant layer.

[0040] The melt strength (180° C.) of the ionomer can be measured in accordance with JIS K 7199, for example.

[0041] The ionomer contained in the follow-up layer 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 portion and metal ions.

[0042] Examples of the metal ion include sodium ions, zinc ions, etc. In this specification, an ionomer in which the metal ion is a sodium ion may be referred to as a sodium-based ionomer, and an ionomer in which the metal ion is a zinc ion may be referred to as a zinc-based ionomer.

[0043] The following layer may contain only one type of ionomer, 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.

[0044] The following layer may contain only an ionomer (i.e., it may consist of an ionomer), or it may contain an ionomer and other components (sometimes referred to as "other components" in this specification) (i.e., it may consist of an ionomer and the other components).

[0045] The other components contained in the follow-up layer are not particularly limited and can be selected arbitrarily depending on the purpose, and may be, for example, either a resin component or a non-resin component. The other component, which is a resin component, is a resin other than an ionomer. The other component (resin other than ionomer) which is a resin component may be a homopolymer which is a polymer of one type of monomer, or a copolymer which is a polymer of two or more types of monomers. Examples of the other components that are non-resin components include the same additives as those listed above as other components contained in the sealant layer.

[0046] The other components contained in the follow-up 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.

[0047] The proportion of the ionomer content in the following layer relative to the total mass of the following layer is preferably 50% by mass or more, more preferably 55 to 100% by mass, and even more preferably 60 to 100% by mass, and may be, for example, any of 70 to 100% by mass and 85 to 100% by mass. When the proportion is equal to or greater than the lower limit, the multilayer film can better conform to the contents contained therein when used to form a package. The ratio is usually the same as the ratio of the content (parts by mass) of the ionomer to the total content (parts by mass) of components that do not vaporize at room temperature in the composition for forming the follow-up layer, which will be described later.

[0048] The following layer may be composed of one layer (single layer) or two or more layers. When the following 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.

[0049] The thickness of the conforming layer is preferably 4 to 90 μm, more preferably 5 to 70 μm, and even more preferably 6 to 50 μm. When the thickness of the conforming layer is equal to or greater than the lower limit, the conforming ability of the multilayer film to the contents contained therein is improved when a package is formed using the multilayer film. When the thickness of the conforming layer is equal to or less than the upper limit, the conforming layer is prevented from becoming excessively thick. Here, "thickness of the follower layer" means the thickness of the entire follower layer, and for example, the thickness of a follower layer consisting of multiple layers means the total thickness of all layers that make up the follower layer.

[0050] The thickness of the follower layer (in FIG. 1, the thickness T1 of the multilayer film 1) relative to the thickness of the follower layer (in FIG. 1, the thickness T 12 The proportion of the thickness of the multilayer film (sometimes simply referred to herein as "proportion of the thickness of the conforming layer") is not particularly limited, but is preferably 5% or more, more preferably 5 to 50%, and even more preferably 5 to 40%. When the proportion is equal to or greater than the lower limit, the conformability of the multilayer film to the contents contained in a package formed using the multilayer film is improved. When the proportion is equal to or less than the upper limit, the thickness of the conforming layer is prevented from becoming excessive.

[0051] <Gas barrier layer> The gas barrier layer (gas barrier layer 13 in the multilayer film 1 shown in FIG. 1) imparts strong gas barrier properties (in other words, the property of inhibiting gas permeation) to the multilayer film. Here, examples of gas barrier properties include oxygen barrier properties (in other words, the property of inhibiting oxygen gas permeation).

[0052] The gas barrier layer preferably contains either or both of ethylene-vinyl alcohol copolymer (EVOH, also known as saponified ethylene-vinyl acetate copolymer) and polyvinylidene chloride (PVDC) (these resins may be collectively referred to as "gas barrier resins" in this specification), and more preferably contains ethylene-vinyl alcohol copolymer. The gas barrier properties of a multilayer film having such a gas barrier layer are further improved.

[0053] The gas barrier layer may contain only the gas barrier property-imparting resin (i.e., it may consist of the gas barrier property-imparting resin), or it may contain the gas barrier property-imparting resin and other components (sometimes referred to as "other components" in this specification) (i.e., it may consist of the gas barrier property-imparting resin and the other components).

[0054] The other components contained in the gas barrier layer are not particularly limited and can be selected arbitrarily depending on the purpose, and may be, for example, either a resin component or a non-resin component. The other resin component is a resin other than the gas barrier property-imparting resin (ethylene-vinyl alcohol copolymer and polyvinylidene chloride). Examples of the other components that are non-resin components include the same additives as those listed above as other components contained in the sealant layer.

[0055] 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.

[0056] The proportion of the gas barrier resin content (total content of ethylene-vinyl alcohol copolymer and polyvinylidene chloride) in the gas barrier layer relative to the total mass of the gas barrier layer is preferably 50 to 100 mass%, more preferably 60 to 100 mass%, and even more preferably 70 to 100 mass%, and may be, for example, 85 to 100 mass%. When this proportion is equal to or greater than the lower limit, the gas barrier property of the multilayer film is further improved. This ratio is usually the same as the ratio of the content (parts by mass) of the gas barrier property-imparting 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, which will be described later.

[0057] 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, and the combination of these multiple layers is not particularly limited as long as it does not impair the effects of the present invention.

[0058] The thickness of the gas barrier layer 14 is preferably 1 to 100 μm, more preferably 1.5 to 90 μm, and even more preferably 2 to 80 μm, and may be, for example, any of 4 to 60 μm, 4 to 40 μm, and 4 to 30 μm. 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 are improved. This is because, for example, a thicker gas barrier layer not only improves the gas barrier properties but also prevents the occurrence of so-called "layer breaks," in which a portion of the gas barrier layer is not formed in the multilayer film due to a gas barrier layer that is too thin. When the thickness of the gas barrier layer is equal to or less than the upper limit, the gas barrier layer is prevented from becoming excessively thick. Furthermore, this prevents, for example, a decrease in the conformability of the multilayer film to the contents when a package is formed using the multilayer film. Here, the "thickness of the gas barrier layer" means the thickness of the entire gas barrier layer, and for example, the thickness of a gas barrier layer consisting of multiple layers means the total thickness of all layers that make up the gas barrier layer.

[0059] The thickness of the gas barrier layer (thickness T1 of the multilayer film 1 in FIG. 1) relative to the thickness of the multilayer film (thickness T2 of the gas barrier layer 13 in FIG. 1) 13 ) (sometimes simply referred to herein as "gas barrier layer thickness ratio") is 2 to 25%, and may be, for example, any of 2 to 18%, 2 to 12%, and 2 to 7%, or any of 8 to 25%, 13 to 25%, and 17 to 25%, or may be 8 to 18%. When the ratio is equal to or greater than the lower limit, the gas barrier properties of the multilayer film are improved. This is because, for example, an increased thickness of the gas barrier layer improves the gas barrier properties, and also prevents the occurrence of so-called "layer breaks," in which part of the gas barrier layer is not formed in the multilayer film due to an excessively thin gas barrier layer. When the ratio is equal to or less than the upper limit, the gas barrier layer is prevented from becoming excessively thick. Furthermore, this prevents, for example, a decrease in the conformability of the multilayer film to the contents when a package is formed using the multilayer film.

[0060] In the case of skin pack packaging for food, the multilayer film constituting the skin pack packaging is required to have a gas barrier layer to prevent oxidative deterioration of the food. However, the presence of the gas barrier layer has the problem of reducing the conformability of the skin pack packaging to the food (its ability to adhere to the food without causing wrinkles). In contrast, the skin pack packaging constructed using the multilayer film of this embodiment has improved this problem as described above.

[0061] <Outer layer> The outer layer (outer layer 15 in the multilayer film 1 shown in Figure 1) can be, for example, a layer that protects the entire multilayer film; a layer that improves the ability of the multilayer film to conform to the contents when a package is made using the multilayer film; etc. When the outer layer is one of the outermost layers of the multilayer film, the surface of the outer layer opposite to the sealant layer side (first surface) is the exposed surface.

[0062] The outer layer may be, for example, a resin layer containing one or more resins selected from the group consisting of polyolefin resins, polyesters, and polyamides (in this specification, these resins may be collectively referred to as "outer layer resin").

[0063] The polyolefin resin is a resin having structural units derived from an olefin, and may have structural units derived from only one type of olefin, or may have structural units derived from two or more types of olefins. The polyolefin resin is preferably a polyethylene resin (polyethylene, ethylene copolymer), more preferably polyethylene.

[0064] Examples of the polyethylene resin contained in the outer layer include the same polyethylene resins as those listed above as the resins contained in the sealant layer.

[0065] Examples of polyesters contained in the outer layer include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), and glycol-modified polyethylene terephthalate (PETG).

[0066] Examples of polyamides contained in the outer layer include 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, copolymer of 6-nylon and 66-nylon (nylon 6 / 66), copolymer of 6-nylon and 610-nylon, copolymer of 6-nylon and 611-nylon, copolymer of 6-nylon and 12-nylon (nylon 6 / 12), copolymer of 6-nylon and 612 nylon, 6 copolymers of 6-nylon and 6T-nylon, copolymers of 6-nylon and 6I-nylon, copolymers of 6-nylon, 66-nylon and 610-nylon, copolymers of 6-nylon, 66-nylon and 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.

[0067] In terms of heat resistance, mechanical strength, availability, and the like, the polyamide is preferably 6-nylon, 12-nylon, 66-nylon, nylon 6 / 66, nylon 6 / 12, or nylon 6 / 66 / 12.

[0068] The outer layer may contain only the outer layer resin (i.e., it may consist of the outer layer resin), or it may contain the outer layer resin and other components (sometimes referred to as "other components" in this specification) (i.e., it may consist of the outer layer resin and the other components).

[0069] The outer layer may contain only one type of outer layer resin, 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.

[0070] The other components contained in the outer layer are not particularly limited and can be selected arbitrarily depending on the purpose, and may be, for example, either a resin component or a non-resin component. The other resin components are resins other than the outer layer resin (polyolefin resin, polyester, and polyamide). Examples of the other components that are non-resin components include the same additives as those listed above as other components contained in the sealant layer.

[0071] The outer 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.

[0072] The proportion of the outer layer resin content (total content of polyolefin resin, polyester, and polyamide) relative to the total mass of the outer layer ([total amount of polyolefin resin, polyester, and polyamide in outer layer (parts by mass)] / [total mass of outer layer (parts by mass)]×100) is preferably 50% by mass or more, more preferably 55 to 100% by mass, and even more preferably 60 to 100% by mass, and may be, for example, any of 70 to 100% by mass and 85 to 100% by mass. When the proportion is equal to or greater than the lower limit, the effect obtained by having an outer layer in a multilayer film is enhanced. The ratio is usually the same as the ratio of the content (parts by mass) of the outer layer resin to the total content (parts by mass) of components that do not vaporize at room temperature in the composition for forming the outer layer, which will be described later.

[0073] The outer layer may consist of one layer (single layer) or two or more layers. When the outer 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.

[0074] The thickness of the outer layer is not particularly limited, but is preferably 5 to 140 μm, more preferably 5 to 120 μm, and even more preferably 5 to 100 μm, and may be, for example, either 5 to 80 μm or 5 to 60 μm. When the thickness of the outer layer is equal to or greater than the lower limit, the effect obtained by providing the outer layer in the multilayer film is enhanced. When the thickness of the outer layer is equal to or less than the upper limit, the outer layer is prevented from becoming excessively thick. Here, the "thickness of the outer layer" means the thickness of the entire outer layer, and for example, the thickness of an outer layer consisting of multiple layers means the total thickness of all layers that make up the outer layer.

[0075] The ratio of the thickness of the outer layer to the thickness of the multilayer film is not particularly limited, but is preferably 3% or more, more preferably 3 to 55%, and even more preferably 3 to 40%. When the ratio is equal to or greater than the lower limit, the effect obtained by providing the outer layer in the multilayer film is enhanced. When the ratio is equal to or less than the upper limit, the outer layer is prevented from becoming excessively thick.

[0076] <Pinhole-resistant layer> The multilayer film has the pinhole-resistant layer (pinhole-resistant layer 14 in the multilayer film 1 shown in FIG. 1 ), which enhances its pinhole resistance (the effect of suppressing damage such as holes and tears). Furthermore, a package constructed using this multilayer film can be prevented from losing strength during heat treatment.

[0077] The pinhole-resistant layer preferably contains polyamide. When the pinhole-resistant layer contains polyamide, the pinhole resistance of the multilayer film is improved.

[0078] Examples of the polyamide contained in the pinhole-resistant layer include the same polyamides as those listed above as the polyamides contained in the outer layer.

[0079] The pinhole-resistant layer may contain only one type of polyamide, 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.

[0080] The pinhole-resistant layer may contain only polyamide (i.e., it may consist of polyamide), or it may contain polyamide and other components (sometimes referred to as "other components" in this specification) (i.e., it may consist of polyamide and the other components).

[0081] The other components contained in the pinhole-resistant layer are not particularly limited and can be selected arbitrarily depending on the purpose, and may be, for example, either a resin component or a non-resin component. The other component, which is a resin component, is a resin other than polyamide. Examples of the other components that are non-resin components include the same additives as those listed above as other components contained in the sealant layer.

[0082] The other components contained in the pinhole-resistant 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.

[0083] The proportion of the polyamide content in the pinhole-resistant layer relative to the total mass of the pinhole-resistant layer is preferably 50% by mass or more, more preferably 55 to 100% by mass, and even more preferably 60 to 100% by mass, and may be, for example, any of 70 to 100% by mass and 85 to 100% by mass. When the proportion is equal to or greater than the lower limit, the pinhole resistance of the multilayer film is further improved. The ratio is usually the same as the ratio of the polyamide content (parts by mass) to the total content (parts by mass) of components that do not vaporize at room temperature in the composition for forming a pinhole-resistant layer, which will be described later.

[0084] The pinhole-resistant layer may consist of one layer (single layer) or two or more layers. When the pinhole-resistant 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.

[0085] The thickness of the pinhole-resistant layer is preferably 3 to 60 μm, more preferably 3 to 50 μm, and even more preferably 4 to 40 μm, and may be, for example, 4 to 10 μm or 10 to 40 μm. When the thickness of the pinhole-resistant layer is at least the above lower limit, the pinhole resistance of the multilayer film is further improved. When the thickness of the pinhole-resistant layer is at most the above upper limit, the pinhole-resistant layer is prevented from becoming excessively thick. Here, "thickness of the pinhole-resistant layer" means the thickness of the entire pinhole-resistant layer; for example, the thickness of a pinhole-resistant layer consisting of multiple layers means the total thickness of all layers that make up the pinhole-resistant layer.

[0086] The ratio of the thickness of the pinhole-resistant layer to the thickness of the multilayer film is not particularly limited, but is preferably 2% or more, more preferably 2 to 50%, and even more preferably 3 to 33%, and may be, for example, 3 to 8% or 8 to 33%. When the ratio is equal to or greater than the lower limit, the pinhole resistance of the multilayer film is further improved. When the ratio is equal to or less than the upper limit, the pinhole-resistant layer is prevented from becoming excessively thick.

[0087] <Adhesive layer> The adhesive layer (adhesive layer 16 (first adhesive layer 161, second adhesive layer 162) in the multilayer film 1 shown in FIG. 1) contains an adhesive. The adhesive layer adheres two adjacent layers on either side of the adhesive layer.

[0088] 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).

[0089] 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.

[0090] 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. Examples of the ionomer contained in the adhesive layer include the same ionomers as those listed above as the ionomers contained in the follow-up layer.

[0091] 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.

[0092] 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).

[0093] The adhesive layer 15 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.

[0094] The adhesive layer may contain only an adhesive (i.e., it may consist of an adhesive), or it may contain an adhesive and other components (sometimes referred to as "other components" in this specification) (i.e., it may consist of an adhesive and the other components).

[0095] The other components contained in the adhesive layer are not particularly limited and can be selected arbitrarily depending on the purpose, and may be, for example, either a resin component or a non-resin component.

[0096] 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.

[0097] The content of the adhesive in the adhesive layer relative to the total mass of the adhesive layer may be, for example, 50 to 100 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.

[0098] 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.

[0099] The thickness of the adhesive layer is preferably 4 to 96 μm, more preferably 4 to 93 μm, and may be, for example, any one of 4 to 80 μm, 4 to 60 μm, 4 to 40 μm, and 4 to 20 μm. When the thickness of the adhesive layer is equal to or greater than the lower limit, the adhesive strength between the two layers to be bonded 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. Here, "thickness of adhesive layer" means the thickness of the entire adhesive layer (for example, the thickness of the entire first adhesive layer 161 shown in Figure 1, the thickness of the entire second adhesive layer 162 shown in Figure 1), and for example, the thickness of an adhesive layer consisting of multiple layers means the total thickness of all layers that make up the adhesive layer.

[0100] <Other layers> The multilayer film may also have other layers that do not fall under any of the sealant layer, follow-up layer, gas barrier layer, pinhole-resistant layer, outer layer, and adhesive layer, as long as the effects of the present invention are not impaired.

[0101] The type and arrangement of the other layer are not particularly limited and can be selected arbitrarily depending on the purpose.

[0102] The multilayer film may have only one type of other layer, or two or more types. When there are two or more types, the combination and ratio of the layers can be selected arbitrarily depending on the purpose.

[0103] The other layers may each consist of one layer (single layer) or two or more layers. When the other layers consist 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.

[0104] The thickness of the other layer can be set arbitrarily depending on the type of the other layer, and is not particularly limited.

[0105] When the multilayer film includes the other layer, it may further include an adhesive layer (for example, a layer similar to adhesive layer 15 shown in Figure 1) for adhering the other layer to other layers.

[0106] The thickness of the multilayer film is preferably 60 μm or more, more preferably 70 to 400 μm, and even more preferably 80 to 300 μm, and may be, for example, 100 to 200 μm. When the thickness of the multilayer film is equal to or greater than the lower limit, the strength of the multilayer film is further improved. When the thickness of the multilayer film is equal to or less than the upper limit, the multilayer film is prevented from becoming excessively thick.

[0107] The oxygen permeability of the multilayer film measured in accordance with JIS K 7126-2:2006 under conditions of a temperature of 23°C and a relative humidity of 60% is 100 cc / (m 2 ·day·atm) or less, and 80cc / (m 2 ·day·atm) or less, and 60cc / (m 2 ·day·atm) or less is more preferable, and 40cc / (m 2 ·day·atm) or less is more preferable, and 20cc / (m 2 ·day·atm) or less, for example, 8cc / (m 2 ·day · atm) or less, and 4cc / (m 2 When the oxygen transmission rate of the multilayer film is equal to or less than the upper limit, deterioration of the contents due to oxidation is significantly suppressed when the multilayer film is used (for example, as a lid material) to form a package.

[0108] The lower limit of the oxygen transmission rate of the multilayer film is not particularly limited. For example, the oxygen permeability of the multilayer film is 0.1 cc / (m 2 ·day·atm) or more.

[0109] The oxygen permeability of the multilayer film is, for example, 0.1 to 100 cc / (m2 ·day·atm), 0.1~80cc / (m 2 ·day·atm), 0.1~60cc / (m 2 ·day·atm), 0.1~40cc / (m 2 ·day·atm), 0.1~20cc / (m 2 ·day·atm), 0.1~8cc / (m 2 ·day·atm), and 0.1~4cc / (m 2 ·day·atm) or any of the following:

[0110] The oxygen permeability of the multilayer film can be adjusted by, for example, adjusting the type and content of the components contained in the gas barrier layer, the thickness of the gas barrier layer, and the like.

[0111] The dynamic elastic modulus E' of the multilayer film at a temperature of 140°C (sometimes referred to as "E'(140°C)" in this specification) is, for example, 8 x 10 6 ~2×10 10 Pa may be 8 x 10 6 ~1×10 10 Pa, and 1 x 10 7 ~2×10 10 It may be either 1 x 10 Pa or 1 x 10 7 ~1×10 10 Pa, for example, 1×10 8 ~1×10 10 Pa, and 1 x 10 9 ~1×10 10 It may be either 1 x 10 Pa or 1 x 10 7 ~1×10 9 Pa, and 1 x 10 7 ~1×10 8 It may be either 1 x 10 Pa or 1 x 10 8 ~1×10 9Pa. When E'(140°C) is equal to or greater than the lower limit, damage (holes, tears, etc.) to the multilayer film (lid material) due to contact with the contents when a package is constructed using the multilayer film (lid material) is further suppressed. When E'(140°C) is equal to or less than the upper limit, conformability of the multilayer film to the contents when a package is constructed using the multilayer film is further improved. Furthermore, when a package is constructed using the multilayer film as a lid material and a base material, deformation of the base material is more effectively suppressed.

[0112] E'(140°C) can be measured by preparing a test piece of the multilayer film and subjecting the test piece to dynamic viscoelasticity measurement (DMA) in a tensile mode in the temperature range of 25°C to 160°C under the conditions of a displacement of 10 μm, a vibration frequency of 1 Hz, and a heating rate of 3°C / min in accordance with JIS K7244-4. The test piece may be, for example, 4 mm wide and 5 cm or longer.

[0113] E'(140°C) can be adjusted, for example, by adjusting the type and content of the components contained in the gas barrier layer, the thickness of the gas barrier layer, etc. This is because many of the resin components contained in the gas barrier layer, such as the gas barrier property-imparting resin, have a relatively high dynamic modulus of elasticity E'.

[0114] The multilayer film of the present embodiment is not limited to the above, and some of the configuration may be changed, deleted, or added within the scope of the gist of the present invention.

[0115] For example, the multilayer film of the present embodiment may have at least a sealant layer, a follower layer, and a gas barrier layer, and the other layers may have any configuration, and layers that do not fall into the category of a sealant layer, a follower layer, or a gas barrier layer may be selected arbitrarily depending on the purpose. However, the multilayer film preferably comprises a sealant layer, a conforming layer, and a gas barrier layer, and further comprises either or both of an outer layer and a pinhole-resistant layer, and may further comprise an adhesive layer. It is more preferable that the multilayer film comprises a sealant layer, a conforming layer, an adhesive layer, a pinhole-resistant layer, a gas barrier layer, an adhesive layer, and an outer layer in this order, as shown in Figure 1.

[0116] It is preferred that all layers of the multilayer film of the present embodiment are transparent, i.e., that the multilayer film is a transparent multilayer film. In a package constructed using such a multilayer film, the contents can be easily seen through the multilayer film.

[0117] <<Multilayer film manufacturing method>> The multilayer film of this embodiment can be produced, for example, by a feedblock 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.

[0118] The multilayer film of this embodiment can also be produced by coating the surface of another layer that will form one of the layers with a resin, resin composition, etc., and drying it as needed to form a laminated structure in the multilayer film, and then, as needed, further laminating other layers so as to achieve the desired arrangement.

[0119] The multilayer film of this embodiment can also be produced by separately preparing two or more films for constituting any two or more of the layers, laminating these films together using an adhesive by any of dry lamination, extrusion lamination, hot melt lamination, and wet lamination, and then laminating other layers as needed to form the desired arrangement. In this case, the adhesive used may be one capable of forming the adhesive layer.

[0120] The multilayer film of this embodiment can also be produced by laminating two or more films that have been prepared separately in advance, as described above, by a thermal lamination method or the like without using an adhesive, and then further laminating other layers as needed to achieve the desired arrangement.

[0121] When producing the multilayer film of this embodiment, two or more of the methods for forming any of the layers (films) in the multilayer film described above may be combined.

[0122] Regardless of the manufacturing method, the resin composition that forms one of the layers in the multilayer film may be manufactured by adjusting the types and contents of the components contained therein so that the layer to be formed contains the desired components (constituent materials) 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.

[0123] Examples of 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 Figure 1) include those containing the polyethylene resin and, if necessary, the other components described above.

[0124] Examples of resin compositions (sometimes referred to in this specification as "compositions for forming a follower layer") for forming a follower layer (follower layer 12 in the multilayer film 1 shown in Figure 1) include those containing the ionomer and, if necessary, the other components.

[0125] Examples of resin compositions (sometimes referred to herein as "gas barrier layer-forming compositions") for forming a gas barrier layer (gas barrier layer 13 in the multilayer film 1 shown in FIG. 1) include those containing the gas barrier property-imparting resin and, if necessary, the other components described above.

[0126] Examples of resin compositions (sometimes referred to herein as "compositions for forming outer layers") for forming outer layers (outer layer 15 in the multilayer film 1 shown in Figure 1) include those containing the outer layer resin and, if necessary, the other components.

[0127] Examples of resin compositions (sometimes referred to in this specification as "compositions for forming pinhole-resistant layers") for forming pinhole-resistant layers (pinhole-resistant layer 14 in the multilayer film 12 shown in Figure 1) include those containing the polyamide and, if necessary, the other components described above.

[0128] Examples of resin compositions (sometimes referred to in this specification as "adhesive layer-forming compositions") for forming an adhesive layer (adhesive layer 16 in the multilayer film 1 shown in Figure 1) include those containing the adhesive and, if necessary, the other components described above.

[0129] <<Packaging>> A package according to one embodiment of the present invention includes the multilayer film according to one embodiment of the present invention described above. The packaging body of this embodiment has oxygen barrier properties, and in particular the multilayer film has high conformability to the contents contained therein, so that damage to the multilayer film due to contact with the contents is suppressed. The packaging body of this embodiment is suitable as a skin pack packaging body. For example, such a packaging body may be configured to include a lid material that is the multilayer film and a base material.

[0130] <<One embodiment of the base material>> The base material is preferably a laminated body formed by laminating a plurality of layers. A preferred example of a base material that is a laminate is a resin laminate that includes a foamed resin layer and a non-foamed resin layer provided on the foamed resin layer.

[0131] The foamed resin layer may be a known one. The foamed resin layer may be, for example, a resin layer containing a foamed polystyrene resin (PSP).

[0132] The density of the foamed resin layer is not particularly limited, but is preferably 0.05 to 0.5 g / cm 3 It is preferable that: The expansion ratio of the foamed resin layer is not particularly limited, but is preferably 2 to 20 times. The thickness of the foamed resin layer is not particularly limited, but is preferably 500 to 6000 μm.

[0133] The non-foamed resin layer may be, for example, a multi-layer film for base materials, which is constructed by laminating an easy-peel layer, a gas barrier layer, a pinhole-resistant layer, and an adhesive layer in this order in the thickness direction, wherein the easy-peel layer is one of the outermost layers and the adhesive layer is the other outermost layer.

[0134] The multi-layer film for base materials may include, for example, an intermediate adhesive layer between the easy-peel layer and the gas barrier layer for bonding these two layers together. The multi-layer film for base materials may also include, for example, an intermediate adhesive layer between the gas barrier layer and the pinhole-resistant layer for bonding these two layers together. That is, the multilayer film for base materials may be constructed by laminating an easy-peel layer, an intermediate adhesive layer, a gas barrier layer, an intermediate adhesive layer, a pinhole-resistant layer, and an adhesive layer in this order in the thickness direction.

[0135] In this specification, in order to distinguish these two intermediate adhesive layers from each other, the intermediate adhesive layer located between the easy-peel layer and the gas barrier layer may be referred to as the first intermediate adhesive layer, and the intermediate adhesive layer located between the gas barrier layer and the pinhole-resistant layer may be referred to as the second intermediate adhesive layer, as necessary. These two intermediate adhesive layers (first intermediate adhesive layer, second intermediate adhesive layer) may be the same as or different from each other.

[0136] <Easy-peel layer> The easy peel layer in the multi-layer film for base materials may be one that exhibits peelability by cohesive failure. An example of an easy-peel layer that exhibits peelability by cohesive failure is one that contains two incompatible polyolefins.

[0137] Examples of the two incompatible polyolefins contained in the easy-peel layer of the multilayer film for base materials include an ethylene-based polymer having at least a structural unit derived from ethylene and a propylene-based polymer having at least a structural unit derived from propylene. That is, the easy-peel layer may include, for example, an ethylene-based polymer having at least a structural unit derived from ethylene, and a propylene-based polymer having at least a structural unit derived from propylene.

[0138] The ethylene polymer contained in the easy-peel layer of the multi-layer film for base materials includes an ethylene homopolymer and an ethylene copolymer.

[0139] Examples of the ethylene homopolymer include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), metallocene-catalyzed linear low-density polyethylene (mLLDPE), medium-density polyethylene (MDPE), and high-density polyethylene (HDPE).

[0140] 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), 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), and ionomer (ION). Examples of the ionomer include the same ionomers as those listed above as those contained in the follow-up layer in the multilayer film described above.

[0141] The easy-peel layer in the multi-layer film for base materials preferably contains low-density polyethylene as the ethylene polymer, which provides better easy-peel properties.

[0142] Examples of the propylene-based polymer contained in the easy-peel layer of the multi-layer film for base materials include a homopolymer of propylene (that is, polypropylene or homopolypropylene, hPP) and a propylene-based copolymer.

[0143] 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, rPP), propylene-ethylene block copolymer (also known as polypropylene block copolymer, bPP), and the like.

[0144] The easy-peel layer in the multi-layer film for base materials preferably contains polypropylene as the propylene-based polymer, which provides better easy-peel properties.

[0145] The component that exhibits easy peelability contained in the easy peel layer of the multilayer film for base materials may be only one type or two or more types, and when two or more types are used, the combination and ratio thereof can be selected arbitrarily depending on the purpose. For example, when the component that exhibits easy peelability is the above-mentioned two incompatible polyolefins, the easy peel layer may contain only one type or two or more types of these polyolefins.

[0146] In the easy-peel layer of the multilayer film for base materials, the ratio of the content (parts by mass) of the ethylene polymer to the total content (parts by mass) of the ethylene polymer and the propylene polymer is preferably 10 to 90% by mass, and may be, for example, 30 to 90% by mass, 45 to 90% by mass, or 60 to 90% by mass. When this ratio is equal to or greater than the lower limit, the easy-peel property of the easy-peel layer becomes better. When this ratio is equal to or less than the upper limit, the peel strength becomes more stable. The ratio is usually the same as the ratio of the content (parts by mass) of the ethylene-based polymer to the total content (parts by mass) of the ethylene-based polymer and the propylene-based polymer in the composition for forming an easy-peel layer for a base material, which will be described later.

[0147] The easy-peel layer in the multilayer film for base materials may contain other components in addition to the components that exhibit easy-peel properties (for example, the two incompatible polyolefins described above) as long as the easy-peel properties are not impaired. The other components contained in the easy-peel layer may be one kind or two or more kinds, and when there are two or more kinds, the combination and ratio thereof can be selected arbitrarily depending on the purpose.

[0148] Examples of the other components contained in the easy-peel layer in the multi-layer film for base materials include an anti-fogging agent and an anti-blocking agent.

[0149] In the easy-peel layer of the multilayer film for base materials, the ratio of the content of the component that exhibits easy-peel properties to the total mass of the easy-peel layer (for example, the ratio of the combined content of the two incompatible polyolefins described above) is preferably 50 to 100% by mass, more preferably 70 to 100% by mass, and may be, for example, any of 80 to 100% by mass, 90 to 100% by mass, 95 to 100% by mass, 97 to 100% by mass, and 99 to 100% by mass. When this ratio is equal to or greater than the lower limit, the easy-peel property of the easy-peel layer becomes better. The above ratio is usually the same as the ratio of the content (parts by mass) of components that exhibit easy peel properties to the total content (parts by mass) of components that do not evaporate at room temperature in the composition for forming an easy peel layer for base materials described below.

[0150] The easy-peel layer in the multi-layer film for base materials may consist of one layer (single layer) or two or more layers. When the easy-peel 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.

[0151] The thickness of the easy-peel layer in the multilayer film for base materials is preferably 2 to 50 μm. When the thickness of the easy-peel layer is equal to or greater than the lower limit, the seal strength of the easy-peel layer is appropriately increased. When the thickness of the easy-peel layer is equal to or less than the upper limit, the easy-peel property is further increased. Here, "thickness of the easy peel layer" means the thickness of the entire easy peel layer, for example, the thickness of an easy peel layer consisting of multiple layers means the total thickness of all layers that make up the easy peel layer.

[0152] The ratio of the thickness of the easy-peel layer to the thickness of the multilayer film for base material is not particularly limited, but is preferably 5 to 40%. When the ratio is equal to or greater than the lower limit, the seal strength of the easy-peel layer is appropriately increased. When the ratio is equal to or less than the upper limit, the easy-peel property is further increased.

[0153] <Gas barrier layer> The gas barrier layer imparts gas barrier properties (in other words, properties that inhibit gas permeation) to the base multilayer film. Here, examples of gas barrier properties include oxygen barrier properties (in other words, properties that inhibit oxygen gas permeation).

[0154] The gas barrier layer in the multilayer film for base materials preferably contains ethylene-vinyl alcohol copolymer (EVOH, also known as saponified ethylene-vinyl acetate copolymer) or polyamide.

[0155] Examples of the polyamide include the same polyamides as those listed above as those contained in the outer layer of the multilayer film described above.

[0156] In terms of heat resistance, mechanical strength, availability, and the like, the polyamide is preferably 6-nylon (sometimes abbreviated as "Ny6" in this specification), 12-nylon, 66-nylon, nylon 6 / 66, nylon 6 / 12, or nylon 6 / 66 / 12.

[0157] The gas barrier layer in the multilayer film for base materials may contain only one type of polyamide, 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.

[0158] The gas barrier layer in the multilayer film for base materials may contain only one or both of an ethylene-vinyl alcohol copolymer and a polyamide (i.e., it may consist of one or both of an ethylene-vinyl alcohol copolymer and a polyamide), or it may contain one or both of an ethylene-vinyl alcohol copolymer and a polyamide and components other than these (sometimes referred to as "other components" in this specification) (i.e., it may consist of one or both of an ethylene-vinyl alcohol copolymer and a polyamide and the other components).

[0159] The other components contained in the gas barrier layer in the multi-layer film for base material are not particularly limited and can be selected arbitrarily depending on the purpose, and may be, for example, either a resin component or a non-resin component. The other component, which is a resin component, is a resin that does not fall into either an ethylene-vinyl alcohol copolymer or a polyamide. Examples of the other components that are non-resin components include the same additives as those listed above as other components contained in the sealant layer in the multilayer film described above.

[0160] The other components contained in the gas barrier layer of the multilayer film for base material 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.

[0161] In the gas barrier layer in the multilayer film for base material, the proportion of the total content of the ethylene-vinyl alcohol copolymer and polyamide relative to the total mass of the gas barrier layer is preferably 50 to 100 mass%, more preferably 60 to 100 mass%, and may be, for example, either 70 to 100 mass% or 85 to 100 mass%. The ratio is usually the same as the ratio of the total content (parts by mass) of ethylene-vinyl alcohol copolymer and polyamide 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 for base materials described below.

[0162] The gas barrier layer in the multilayer film for base materials 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.

[0163] The thickness of the gas barrier layer in the multilayer film for base material is preferably 2 to 20 μm. When the thickness of the gas barrier layer is equal to or greater than the lower limit, the oxygen barrier property of the gas barrier layer is improved. When the thickness of the gas barrier layer is equal to or less than the upper limit, the gas barrier layer is prevented from becoming excessively thick. Here, the "thickness of the gas barrier layer" means the thickness of the entire gas barrier layer, and for example, the thickness of a gas barrier layer consisting of multiple layers means the total thickness of all layers that make up the gas barrier layer.

[0164] The ratio of the thickness of the gas barrier layer to the thickness of the multi-layer film for base material is not particularly limited, but is preferably 5 to 15%. When the ratio is equal to or greater than the lower limit, the oxygen barrier properties of the multi-layer film for base material are improved. When the ratio is equal to or less than the upper limit, the gas barrier layer is prevented from becoming excessively thick.

[0165] <Pinhole-resistant layer> The pinhole-resistant layer is a layer for protecting the structure of the multi-layer film for base material, for example, by suppressing the occurrence of pinholes in the multi-layer film for base material.

[0166] The pinhole-resistant layer in the multi-layer film for base materials preferably contains polyolefin. Examples of the polyolefin include polyethylenes such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), metallocene-catalyzed linear low-density polyethylene (mLLDPE), medium-density polyethylene (MDPE), and high-density polyethylene (HDPE); and polypropylene.

[0167] The pinhole-resistant layer in the multilayer film for base materials may contain only polyolefin (i.e., it may consist of polyolefin), or it may contain polyolefin and other components (sometimes referred to as "other components" in this specification) (i.e., it may consist of polyolefin and the other components).

[0168] The other components contained in the pinhole-resistant layer in the multi-layer film for base materials are not particularly limited and can be selected arbitrarily depending on the purpose, and may be, for example, either a resin component or a non-resin component. The other component, which is a resin component, is a resin other than polyolefin. Examples of the other components that are non-resin components include the same additives as those listed above as other components contained in the sealant layer in the multilayer film described above.

[0169] The other components contained in the pinhole-resistant layer in the multilayer film for base materials 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.

[0170] The proportion of the polyolefin content in the pinhole-resistant layer in the multilayer film for base materials relative to the total mass of the pinhole-resistant layer is preferably 50 to 100 mass%, more preferably 60 to 100 mass%, and may be, for example, either 70 to 100 mass% or 85 to 100 mass%. The ratio is usually the same as the ratio of the polyolefin content (parts by mass) to the total content (parts by mass) of components that do not vaporize at room temperature in the composition for forming a pinhole-resistant layer for base materials described below.

[0171] The pinhole-resistant layer in the multilayer film for base materials may consist of one layer (single layer) or two or more layers. When the pinhole-resistant 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.

[0172] The thickness of the pinhole-resistant layer in the multilayer film for base materials is preferably 2 to 50 μm. When the thickness of the pinhole-resistant layer is equal to or greater than the lower limit, the protective ability of the pinhole-resistant layer is enhanced. When the thickness of the pinhole-resistant layer is equal to or less than the upper limit, the pinhole-resistant layer is prevented from becoming excessively thick. Here, "thickness of the pinhole-resistant layer" means the thickness of the entire pinhole-resistant layer; for example, the thickness of a pinhole-resistant layer consisting of multiple layers means the total thickness of all layers that make up the pinhole-resistant layer.

[0173] The ratio of the thickness of the pinhole-resistant layer to the thickness of the multi-layer film for base materials is not particularly limited, but is preferably 5 to 40%. When this ratio is equal to or greater than the lower limit, the pinhole resistance of the multi-layer film for base materials is improved. When this ratio is equal to or less than the upper limit, the pinhole-resistant layer is prevented from becoming excessively thick.

[0174] <Adhesive layer> The adhesive layer is a layer for adhering the base multi-layer film to the foamed resin layer, and contains an adhesive.

[0175] The adhesive is preferably an adhesive resin, more preferably an ethylene-vinyl acetate copolymer resin. The ethylene-vinyl acetate copolymer resin has a structural unit derived from ethylene and a structural unit derived from vinyl acetate, and may or may not have other structural units. A preferred example of the ethylene-vinyl acetate copolymer resin is a partially saponified ethylene-vinyl acetate copolymer.

[0176] The adhesive layer in the multilayer film for base materials may contain only an adhesive (i.e., it may consist of an adhesive), or it may contain an adhesive and other components (sometimes referred to as "other components" in this specification) (i.e., it may consist of an adhesive and the other components).

[0177] The adhesive layer in the multi-layer film for base materials may contain only one type of adhesive, or two or more types. When two or more types are used, the combination and ratio of the adhesives can be selected as desired depending on the purpose.

[0178] The other components contained in the adhesive layer in the multi-layer film for base materials are not particularly limited and can be selected arbitrarily depending on the purpose, and may be, for example, either a resin component or a non-resin component.

[0179] The other components contained in the adhesive layer in the multi-layer film for base materials 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.

[0180] The content of the adhesive in the adhesive layer in the multi-layer film for a base material may be, for example, 50 to 100% by mass relative to the total mass of the adhesive layer. 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 composition for forming an adhesive layer for a base material, which will be described later.

[0181] The adhesive layer in the multi-layer film for base materials 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.

[0182] The thickness of the adhesive layer in the multi-layer film for base materials is preferably 2 to 40 μm. When the thickness of the adhesive layer is equal to or greater than the lower limit, the adhesive strength between the two layers to be bonded 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. Here, "thickness of adhesive layer" means the thickness of the entire adhesive layer; for example, the thickness of an adhesive layer consisting of multiple layers means the total thickness of all layers that make up the adhesive layer.

[0183] The ratio of the thickness of the adhesive layer to the thickness of the multi-layer film for base materials is not particularly limited, but is preferably 5 to 40%. When the ratio is equal to or greater than the lower limit, the adhesive strength between the two layers to be bonded is increased. When the ratio is equal to or less than the upper limit, the adhesive layer is prevented from becoming excessively thick.

[0184] <First intermediate adhesive layer, second intermediate adhesive layer> The first and second intermediate adhesive layers include an adhesive. The adhesive is preferably an adhesive resin. Examples of the adhesive resin include polyolefin resins. The polyolefin resin is a resin having structural units derived from an olefin, and may be a modified polyolefin such as an acid-modified polyolefin having an acidic group (for example, acid-modified polyethylene, acid-modified polypropylene). Examples of polyolefin resins include ethylene copolymers, propylene copolymers, butene copolymers, and modified products of these copolymers (in other words, modified copolymers). The polyolefin resin is preferably a random copolymer, a graft copolymer or a block copolymer, in terms of further improving adhesiveness.

[0185] Examples of the ethylene copolymer include the ethylene copolymers described above as being contained in the easy-peel layer, and modified products thereof (modified copolymers). Examples of the propylene copolymer include a copolymer of propylene and a vinyl group-containing monomer, a modified product thereof (modified copolymer), etc. More specific examples of such a propylene copolymer include maleic anhydride-grafted modified linear low-density polypropylene, a propylene-based thermoplastic elastomer, etc. Examples of the butene copolymer 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).

[0186] The first intermediate adhesive layer and the second intermediate adhesive layer may contain only adhesive (i.e., may consist of adhesive), or may contain adhesive and other components (sometimes referred to as "other components" in this specification) (i.e., may consist of adhesive and the other components).

[0187] The adhesive contained in the first intermediate adhesive layer and the second intermediate adhesive layer may be one type only or two or more types, and if there are two or more types, the combination and ratio thereof can be selected arbitrarily depending on the purpose.

[0188] The other components contained in the first intermediate adhesive layer and the second intermediate adhesive layer are not particularly limited and can be selected arbitrarily depending on the purpose, and may be, for example, either a resin component or a non-resin component.

[0189] The other components contained in the first intermediate adhesive layer and the second intermediate adhesive layer may be one type only or two or more types, and if there are two or more types, the combination and ratio thereof can be selected arbitrarily depending on the purpose.

[0190] The content of the adhesive in the first intermediate adhesive layer in the multi-layer film for a base material may be, for example, 50 to 100% by mass relative to the total mass of the first intermediate adhesive layer. This ratio is usually the same as the ratio of the adhesive content (parts by mass) to the total content (parts by mass) of components that do not vaporize at room temperature in the composition for forming the first intermediate adhesive layer for the base material described below. The content of the adhesive in the second intermediate adhesive layer in the multi-layer film for base materials may be, for example, 50 to 100% by mass relative to the total mass of the second intermediate adhesive layer. This ratio is usually the same as the ratio of the adhesive content (parts by mass) to the total content (parts by mass) of components that do not vaporize at room temperature in the composition for forming the second intermediate adhesive layer for the base material described below.

[0191] The first and second intermediate adhesive layers in the multilayer film for base materials may each consist of one layer (single layer) or two or more layers. When the first or second intermediate adhesive 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.

[0192] The thicknesses of the first intermediate adhesive layer and the second intermediate adhesive layer in the multilayer film for base materials are preferably each independently 2 to 15 μm. When the thicknesses of the first intermediate adhesive layer and the second intermediate adhesive layer are equal to or greater than the lower limit, the adhesive strength between the two layers to be bonded is increased. When the thicknesses of the first intermediate adhesive layer and the second intermediate adhesive layer are equal to or less than the upper limit, the first intermediate adhesive layer and the second intermediate adhesive layer are prevented from becoming excessively thick. Here, the "thickness of the first intermediate adhesive layer" refers to the overall thickness of the first intermediate adhesive layer, for example, the thickness of a first intermediate adhesive layer consisting of multiple layers refers to the total thickness of all layers that make up the first intermediate adhesive layer. This also applies to the second intermediate adhesive layer.

[0193] The ratio of the thickness of the first intermediate adhesive layer and the second intermediate adhesive layer to the thickness of the multilayer film for base material is not particularly limited, but is preferably 3 to 20%. When the ratio is equal to or greater than the lower limit, the adhesive strength of the two layers to be bonded is increased. When the ratio is equal to or less than the upper limit, the first intermediate adhesive layer and the second intermediate adhesive layer are prevented from becoming excessively thick.

[0194] <Other layers> The multilayer film for base materials may also have other layers that do not fall under any of the easy-peel layer, the first intermediate adhesive layer, the gas barrier layer, the second intermediate adhesive layer, the pinhole-resistant layer, and the adhesive layer, as long as the effects of the present invention are not impaired.

[0195] The types and positions of the other layers in the multi-layer film for base materials are not particularly limited and can be selected arbitrarily depending on the purpose.

[0196] The other layer provided in the multilayer film for base materials 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.

[0197] The other layers in the multi-layer film for base materials may each consist of one layer (single layer) or two or more layers. When the other layers consist 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.

[0198] The thickness of the other layers in the multi-layer film for base material can be set arbitrarily depending on the type of the other layers, and is not particularly limited.

[0199] When the multilayer film for base materials has the other layer, it may further have an intermediate adhesive layer for adhering the other layer to other layers, and in this case, the intermediate adhesive layer may be, for example, the same as the first intermediate adhesive layer or the second intermediate adhesive layer described above.

[0200] The thickness of the non-foamed resin layer of the multi-layer film for base material is not particularly limited, but is preferably 40 to 120 μm.

[0201] The oxygen permeability of the base material measured in accordance with JIS K 7126-2:2006 under conditions of a temperature of 23°C and a relative humidity of 60% is 20cc / (m 2 ·day·atm) or less, for example, 8cc / (m 2 ·day · atm) or less, and 4cc / (m 2 When the oxygen transmission rate of the base material is equal to or less than the upper limit, deterioration of the contents in the package due to oxidation is significantly suppressed. The lower limit of the oxygen transmission rate of the sole material is not particularly limited. For example, the oxygen permeability of the base material is 0.1 cc / (m 2 ·day·atm) or more.

[0202] The oxygen permeability of the sole material can be more easily adjusted by adjusting, for example, the type and amount of components contained in the sole material, the thickness of the sole material, etc.

[0203] The thickness of the base material is preferably 100 μm or more, more preferably 110 μm or more, and even more preferably 120 μm or more. When the thickness of the base material is equal to or greater than the lower limit, the strength of the base material is further improved. The thickness of the base material is preferably 6000 μm or less. By keeping the thickness of the base material at or below the upper limit value, the base material is prevented from becoming excessively thick. The thickness of the base material can be adjusted appropriately within a range set by any combination of any of the above-mentioned lower limit values ​​and upper limit values.

[0204] Regardless of the type of base material, all layers may be transparent and the base material may be transparent, or all or some of the layers may not be transparent and the base material may not be transparent. In a package constructed using a transparent base material, the contents can be easily seen through the base material.

[0205] <<Sole manufacturing method>> The base material can be produced by a known method depending on the type. For example, when the base material is a resin laminate comprising the above-mentioned foamed resin layer and non-foamed resin layer, the base material can be produced by bonding one side of the foamed resin layer to one side of the non-foamed resin layer (or the adhesive layer therein, when the non-foamed resin layer is the multilayer film for base material) by heat lamination. The heat lamination in this case may be carried out by, for example, a melt-press lamination method as described later in the Examples, or by an extrusion lamination method. Of the non-foamed resin layers, the multilayer film for base material can be produced in the same manner as the multilayer film (lid material) described above, except that the types of resins or resin compositions used to form each layer are different.

[0206] Regardless of the manufacturing method, the resin composition that forms one of the layers in the multi-layer film for base material may be manufactured by adjusting the types and contents of the components contained therein so that the layer to be formed contains the desired components (constituent materials) 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.

[0207] Examples of resin compositions for forming an easy-peel layer in a multilayer film for base materials (sometimes referred to in this specification as "compositions for forming an easy-peel layer for base materials") include those containing a component that exhibits the easy-peel properties and, if necessary, the other components described above.

[0208] Examples of resin compositions for forming a gas barrier layer in a multilayer film for base materials (sometimes referred to in this specification as "compositions for forming a gas barrier layer for base materials") include those containing either or both of an ethylene-vinyl alcohol copolymer and a polyamide, and, if necessary, the other components described above.

[0209] Examples of resin compositions for forming a pinhole-resistant layer in a multilayer film for base materials (sometimes referred to in this specification as "compositions for forming pinhole-resistant layers for base materials") include those containing the polyolefins described above and, if necessary, the other components described above.

[0210] The resin composition for forming the adhesive layer in the multilayer film for base material (sometimes referred to in this specification as the "composition for forming an adhesive layer for base material"), the resin composition for forming the first intermediate adhesive layer (sometimes referred to in this specification as the "composition for forming a first intermediate adhesive layer for base material"), and the resin composition for forming the second intermediate adhesive layer (sometimes referred to in this specification as the "composition for forming a second intermediate adhesive layer for base material") can all contain, for example, the adhesive and, if necessary, the other components described above.

[0211] <<One embodiment of the packaging body>> FIG. 2 is a cross-sectional view schematically showing an example of the packaging body of this embodiment. In FIG. 2 and subsequent figures, the same components as those shown in the figures already described are given the same reference numerals as in the figures already described, and detailed description thereof will be omitted.

[0212] The packaging body 10 shown here is configured to include the multilayer film 1 shown in Fig. 1 and a base material 8. Examples of the base material 8 include those described above. In FIG. 2, the distinction between the layers in the multilayer film 1 is omitted.

[0213] The package 10 is preferably a skin pack package in which the multilayer film 1 is used as a lid material.

[0214] The packaging body 10 has oxygen barrier properties. In the packaging body 10, the multilayer film (lid material) 1 has excellent conformability to the contents 9 contained therein. In the packaging body 10, damage to the multilayer film (lid material) 1 due to contact with the contents 9 is suppressed.

[0215] One surface 8a of the base material 8 (sometimes referred to herein as the "first surface") is a sealing surface, and a portion of the first surface 8a is in close contact with a portion of the second surface 11b of the sealant layer 11 in the multilayer film (lid material) 1 by sealing. In FIG. 2, the area where the first surface 8a of the base material 8 and the second surface 11b of the sealant layer 11 in the multilayer film 1 are in direct contact is the sealed portion. As a result, a storage section 10a is formed between the first surface 8a of the base material 8 and the second surface 11b of the sealant layer 11. An item 9 is sealed in this storage section 10a.

[0216] In Figure 2, some gaps can be seen between the contents 9 and the multilayer film 1, and between the contents 9 and the base material 8 within the storage section 10a of the package 10, but these gaps may not be present in the package 10 when the contents 9 are stored therein.

[0217] In the packaging body 10, the thickness of the flat portion of the lid material 1 is the same as the thickness of the multilayer film described above. In the packaging body 10, the thickness of the base material 8 is the same as the thickness of the base material described above.

[0218] The contents 9 can be selected arbitrarily depending on the purpose and is not particularly limited, but is preferably a food product. In particular, when the contents 9 are hard and distorted, such as frozen foods, the multilayer film 1 is extremely effective in that it prevents damage such as tearing or holes caused by contact with the contents 9.

[0219] The packaging body of this embodiment is not limited to the one described above, and some of the configuration may be changed, deleted, or added within the scope of the spirit of the present invention. For example, Figure 2 shows a packaging body 10 constructed using the multilayer film 1 shown in Figure 1 as the lid material, but the packaging body of this embodiment may also be constructed using a multilayer film other than the multilayer film 1 as the lid material.

[0220] <<Packaging manufacturing method>> The package of this embodiment can be produced by packaging the contents using the multilayer film. For example, a skin pack packaging body using the multilayer film as a lid material and comprising the lid material and base material can be manufactured by placing a content on the surface of the base material that will seal with the lid material, covering the surface of the base material and the content with the lid material from above, and evacuating the area between the base material and the lid material where the content is located, thereby tightly fixing the lid material to the content, while heat-sealing the base material and the lid material in the area where the content is not located.

[0221] The sealing temperature during heat sealing is not particularly limited, but is preferably 100 to 170° C. When the sealing temperature is equal to or higher than the lower limit, for example, the seal strength of the package becomes higher while maintaining easy-peel properties. When the sealing temperature is equal to or lower than the upper limit, the package becomes easier to open.

[0222] The heat-sealing time can be adjusted as appropriate depending on the sealing temperature, but is usually preferably 10 to 30 seconds. When the sealing time is equal to or greater than the lower limit, the package has a higher seal strength while retaining easy-peel properties. When the sealing time is equal to or less than the upper limit, the package is easier to open.

[0223] The pressure in the region where the contents are placed, which is generated by evacuation during heat sealing, is preferably 5000 Pa (50 mbar) or less. When the pressure is equal to or less than the upper limit, the lid material has a higher ability to conform (adhere) to the contents, and a package having better storage suitability can be obtained. [Example]

[0224] 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.

[0225] [Example 1] <<Manufacturing of multilayer film (lid material)>> A multilayer film having the structure shown in FIG. 1 was produced according to the following procedure. That is, low-density polyethylene (LDPE, "F222NH" manufactured by Ube Maruzen Polyethylene Co., Ltd.) was prepared as the resin constituting the sealant layer. In this specification, this LDPE may be referred to as "LDPE (1)." A sodium-based ionomer (ION, "Himilan (registered trademark) 1601" manufactured by Mitsui Dow Polychemicals) was prepared as a resin for forming the follow-up layer. In this specification, this ION may be referred to as "ION (1)". As the resin for forming the pinhole-resistant layer, 6-nylon (6Ny, "1030B2" manufactured by Ube Industries, Ltd.) was prepared. An ethylene-vinyl alcohol copolymer (EVOH, "J171B" manufactured by Kuraray Co., Ltd.) was prepared as the resin for forming the gas barrier layer. Amorphous polyethylene terephthalate (PETG, "S2008" manufactured by SK Chemicals) was prepared as the resin for forming the outer layer. Maleic anhydride-modified polyethylene (modified PE, "Admer (registered trademark) NF536" manufactured by Mitsui Chemicals, Inc.) was prepared as the adhesive (adhesive resin) constituting the first adhesive layer. In this specification, this modified PE may be referred to as "modified PE (1)." As the adhesive (adhesive resin) constituting the second adhesive layer, maleic anhydride-modified polyethylene (modified PE, "F515A" manufactured by Mitsubishi Chemical Corporation) was prepared. In this specification, this modified PE may be referred to as "modified PE (2)."

[0226] The temperature of the die was set at 250°C, and the LDPE(1), ION(1), modified PE(1), 6Ny, EVOH, modified PE(2), and PETG were co-extruded in this order (co-extrusion T-die method) to produce a multilayer film (120 μm thick) in which a sealant layer (12 μm thick), a follow layer (17 μm thick), a first adhesive layer (6 μm thick), a pinhole-resistant layer (20 μm thick), a gas barrier layer (12 μm thick), a second adhesive layer (8 μm thick), and an outer layer (45 μm thick) were laminated in this order in their thickness directions. When manufacturing the package described later, this multilayer film was used as a lid material. In this specification, this multilayer film may be referred to as "lid material (I)".

[0227] <<Evaluation of Multilayer Film>> <Melt Strength of Ionomer (180°C)> In accordance with JIS K 7199, using a capillary rheometer (manufactured by Toyo Seiki Seisakusho Co., Ltd.), the melt strength (180°C) (mN) of the ION(1) was measured by melt strength measurement under the measurement conditions of a winding speed of 15 m / min. The results are shown in Table 1.

[0228] <Measurement of Oxygen Permeability>[[]] For the multilayer film obtained above, under the conditions of a temperature of 23°C and a relative humidity of 60%, in accordance with JIS K 7126-2:2006, the oxygen permeability (cc / (m 2 ·day·atm)) was measured. The results are shown in Table 1.

[0229] <Measurement of E’(140°C)> A test piece (1) with a length of 15 cm and a width of 4 mm was cut out from the multilayer film obtained above. Using a dynamic viscoelasticity measuring device ("DMA 7100" manufactured by Hitachi High-Tech Science Corporation), this test piece (1) was placed in a sample holder so that the length of the measurement target part became 2 cm. Next, in accordance with JIS K7244-4, dynamic viscoelasticity measurement of the multilayer film (test piece (1)) was carried out in a tensile mode in the temperature range of 25°C to 160°C under conditions of a displacement of 10 μm, a vibration frequency of 1 Hz, and a heating rate of 3°C / min, and E'(140°C)(Pa) was measured. The results are shown in Table 1.

[0230] <Evaluation of spreading characteristics of the follow-up layer> The thickness of each layer in the multilayer film obtained above was measured using a polarizing microscope to evaluate the spreading properties of the follow-up layer. The results are shown in Table 1.

[0231] <<Manufacture of soles>> <Manufacturing multi-layer film for base materials> A multi-layer film for a base material was produced according to the following procedure. Specifically, low-density polyethylene (LDPE, manufactured by Sumitomo Chemical Co., Ltd. under the name "L211") and polypropylene (PP, manufactured by Sumitomo Chemical Co., Ltd. under the name "FS2011DG2") were prepared as resins for forming the easy-peel layer. In this specification, this LDPE may be referred to as "LDPE(2)." The above-mentioned EVOH was prepared as the resin constituting the gas barrier layer. The resin constituting the pinhole-resistant layer was metallocene-catalyzed linear low-density polyethylene (mLLDPE, Ube Maruzen Polyethylene Co., Ltd.'s "Yumerit (registered trademark) 1520F" with a density of 0.913 g / cm 3 ) was prepared. As the resin constituting the first intermediate adhesive layer, acid-modified polypropylene (acid-modified PP, adhesive resin, "Admer (registered trademark) QF551" manufactured by Mitsui Chemicals, Inc.) was prepared. The modified PE (1) was prepared as the resin for forming the second intermediate adhesive layer. As the resin constituting the adhesive layer, an ethylene-vinyl acetate copolymer resin (EVA resin, adhesive resin, "MELTHEN (registered trademark) MX02D" manufactured by Tosoh Corporation) was prepared.

[0232] The LDPE (2) (70 parts by mass) and the PP (30 parts by mass) were mixed at room temperature to produce a composition for forming an easy peel layer for a base material.

[0233] The die temperature was set to 250°C, and the composition for forming the easy-peel layer for base materials, the acid-modified PP, the EVOH, the acid-modified PE (1), the mLLDPE, and the EVA-based resin were co-extruded in this order (co-extrusion T-die method) to produce a multilayer film for base materials (70 μm thick) consisting of an easy-peel layer (25.9 μm thick), a first intermediate adhesive layer (5.6 μm thick), a gas barrier layer (8.4 μm thick), a second intermediate adhesive layer (5.6 μm thick), a pinhole-resistant layer (10.5 μm thick), and an adhesive layer (14 μm thick) laminated in this order in the thickness direction.

[0234] <Manufacture of soles> A foamed resin sheet (manufactured by Chuo Chemical Co., Ltd., thickness 3000 μm) containing a foamed polystyrene resin (PSP) was used, and the exposed surface of the adhesive layer of the multi-layer film for base material obtained above was bonded to one side of the sheet by heat lamination to obtain a base material (hereinafter sometimes referred to as "base material (α)"). The foamed resin sheet and the multi-layer film for base material were heat-laminated by melt-press lamination using a roll device equipped with a melt-press roll. The melt-press roll was composed of a heated roll and an opposing roll arranged opposite the heated roll, and the foamed resin sheet and the multi-layer film for base material were bonded together by melt-press lamination at 180°C between the heated roll and the opposing roll.

[0235] <<Evaluation of base material>> <Oxygen transmission rate measurement> The oxygen permeability (cc / (m) of the above-obtained base material was measured in accordance with JIS K 7126-2:2006 under conditions of a temperature of 23°C and a relative humidity of 60%. 2 The oxygen permeability of the base material was measured at 2 cc / (m 2 ·day·atm).

[0236] <<Packaging Manufacturing>> Using a continuous skin pack machine (Multivac "T300"), the heat plate temperature was set to 140°C. The sealant layer in the lid material (I) and the easy-peel layer in the base material (α) were placed opposite each other, and frozen fried chicken (100 g) was placed between the lid material (I) and the base material (α). While evacuating the area where the frozen fried chicken was placed, the edges of the lid material (I) and the base material (α) were heat-sealed at a sealing temperature of 150°C for a sealing time of 10 seconds to produce a skin pack package. During the vacuuming process, the pressure at the area where the frozen fried chicken was placed was set to 3000 Pa (30 mbar). The lid material (I) and base material (α) each measured 20 cm x 20 cm.

[0237] <<Packaging evaluation>> <Check for damage to the lid material> The skin pack packages obtained above were visually observed to check for the presence or absence of damage to the lid material such as holes, tears, etc. The results are shown in the column "Damage to lid material" in Table 4.

[0238] <Check for any areas where the lid is not fitting properly to the contents> When checking for holes in the lid material, the presence or absence of insufficient conformity of the lid material to the frozen fried chicken was also checked. The results are shown in the "Insufficient conformity of lid material" column in Table 4.

[0239] <Check for deformation in the base material> When checking for the presence or absence of holes in the lid material, the presence or absence of deformation in the base material was also checked. The results are shown in the "Deformation of base material" column in Table 4.

[0240] <Checking for discoloration of contents after storage> The skin pack package obtained above was stored at -20°C for 90 days. Next, the frozen fried chicken packaged in the skin pack was visually observed from the lid side to check for surface discoloration. If the oxygen barrier properties of the lid side are insufficient, oxidation reactions will progress in the frozen fried chicken during storage, causing surface discoloration. The results are shown in the "Discoloration of the contents" column in Table 4.

[0241] <<Manufacturing and evaluation of multilayer films, manufacturing and evaluation of packaging materials>> [Example 2] A multilayer film (120 μm thick) was produced by laminating a sealant layer (24 μm thick), a conforming layer (40 μm thick), a first adhesive layer (8 μm thick), a pinhole-resistant layer (24 μm thick), a gas barrier layer (6 μm thick), a second adhesive layer (10 μm thick), and an outer layer (8 μm thick) in this order in the thickness direction in the same manner as in Example 1, except that the 6Ny was used instead of the PETG, the modified PE (1) was used instead of the modified PE (2), and the conditions for co-extrusion of the resins were changed. This multilayer film was then evaluated in the same manner as in Example 1. The results are shown in Table 1. Next, a skin pack package was produced and evaluated in the same manner as in Example 1, except that this multilayer film was used as the lid material (sometimes referred to as "lid material (II)" in this specification) instead of the lid material (I). The results are shown in Table 4.

[0242] [Example 3] A multilayer film (thickness 120 μm) was produced by laminating a sealant layer (thickness 8 μm), a conforming layer (thickness 46 μm), a first adhesive layer (thickness 8 μm), a pinhole-resistant layer (thickness 30 μm), a gas barrier layer (thickness 6 μm), a second adhesive layer (thickness 10 μm), and an outer layer (thickness 12 μm) in this order in the thickness direction in the same manner as in Example 1, except that the 6Ny was used instead of the PETG, the modified PE (1) was used instead of the modified PE (2), and the conditions for co-extrusion of the resins were changed. The multilayer film was then evaluated in the same manner as in Example 1. The results are shown in Table 1. Next, a skin pack package was produced and evaluated in the same manner as in Example 1, except that this multilayer film was used as the lid material (sometimes referred to as "lid material (III)" in this specification) instead of the lid material (I). The results are shown in Table 4.

[0243] [Example 4] A multilayer film (thickness 120 μm) was produced in the same manner as in Example 1, except that the conditions for co-extrusion of the resins were changed. The multilayer film was constructed by laminating a sealant layer (thickness 12 μm), a follow-up layer (thickness 17 μm), a first adhesive layer (thickness 6 μm), a pinhole-resistant layer (thickness 20 μm), a gas barrier layer (thickness 17 μm), a second adhesive layer (thickness 8 μm), and an outer layer (thickness 40 μm) in this order in the thickness direction. The multilayer film was then evaluated in the same manner as in Example 1. The results are shown in Table 1. Next, a skin pack package was produced and evaluated in the same manner as in Example 1, except that this multilayer film was used as the lid material (sometimes referred to as "lid material (IV)" in this specification) instead of lid material (I). The results are shown in Table 4.

[0244] [Example 5] A multilayer film (thickness 120 μm) was produced in the same manner as in Example 1, except that the conditions for co-extrusion of the resins were changed. The multilayer film was constructed by laminating a sealant layer (thickness 12 μm), a follow-up layer (thickness 17 μm), a first adhesive layer (thickness 6 μm), a pinhole-resistant layer (thickness 20 μm), a gas barrier layer (thickness 24 μm), a second adhesive layer (thickness 8 μm), and an outer layer (thickness 33 μm) in this order in the thickness direction. The multilayer film was then evaluated in the same manner as in Example 1. The results are shown in Table 1. Next, a skin pack package was produced and evaluated in the same manner as in Example 1, except that this multilayer film was used as a lid material (sometimes referred to as "lid material (V)" in this specification) instead of lid material (I). The results are shown in Table 4.

[0245] [Example 6] A zinc-based ionomer (ION, "Himilan (registered trademark) 1855" manufactured by Mitsui Dow Polychemicals) was prepared as a resin for forming the follow-up layer. In this specification, this ION may be referred to as "ION (2)". A multilayer film (thickness 120 μm) was produced in the same manner as in Example 1, except that ION (2) was used instead of ION (1). The multilayer film was constructed by laminating a sealant layer (thickness 12 μm), a follow-up layer (thickness 17 μm), a first adhesive layer (thickness 6 μm), a pinhole-resistant layer (thickness 20 μm), a gas barrier layer (thickness 12 μm), a second adhesive layer (thickness 8 μm), and an outer layer (thickness 45 μm) in this order in the thickness direction. The multilayer film was then evaluated in the same manner as in Example 1. The results are shown in Table 2. Next, a skin pack package was produced and evaluated in the same manner as in Example 1, except that this multilayer film was used as the lid material (sometimes referred to as "lid material (VI)" in this specification) instead of the lid material (I). The results are shown in Table 4.

[0246] [Example 7] High density polyethylene (HDPE, "3300F" manufactured by Prime Polymer Co., Ltd.) was prepared as the resin for forming the sealant layer. A multilayer film (120 μm thick) was produced in the same manner as in Example 1, except that the PETG was replaced with the 6Ny, the modified PE (1) was replaced with the modified PE (2), and the HDPE was replaced with the LDPE (1), and the conditions for co-extrusion of the resins were changed. A sealant layer (46 μm thick), a conforming layer (8 μm thick), a first adhesive layer (8 μm thick), a pinhole-resistant layer (30 μm thick), a gas barrier layer (6 μm thick), a second adhesive layer (10 μm thick), and an outer layer (12 μm thick) were laminated in this order in the thickness direction. This multilayer film was then evaluated in the same manner as in Example 1. The results are shown in Table 2. Next, a skin pack package was produced and evaluated in the same manner as in Example 1, except that this multilayer film was used as the lid material (sometimes referred to as "lid material (VII)" in this specification) instead of the lid material (I). The results are shown in Table 4.

[0247] [Example 8] As the resin for forming the sealant layer, an ethylene-vinyl acetate copolymer (EVA, "V5714C" manufactured by Mitsui Dow Polychemicals) was prepared. A multilayer film (120 μm thick) was produced in the same manner as in Example 1, except that the LDPE (1) was used instead of the PETG, the EVA was used instead of the LDPE (1), the modified PE (1) was used instead of the modified PE (2), and the conditions for co-extrusion of the resins were changed. The multilayer film was then produced in the same manner as in Example 1, except that the sealant layer (30 μm thick), the conforming layer (29 μm thick), the first adhesive layer (7 μm thick), the pinhole-resistant layer (5 μm thick), the gas barrier layer (5 μm thick), the second adhesive layer (14 μm thick), and the outer layer (30 μm thick) were laminated in this order in the thickness direction. The multilayer film was then evaluated in the same manner as in Example 1. The results are shown in Table 2. Next, a skin pack package was produced and evaluated in the same manner as in Example 1, except that this multilayer film was used as the lid material (sometimes referred to as "lid material (VIII)" in this specification) instead of the lid material (I). The results are shown in Table 5.

[0248] [Comparative Example 1] A multilayer film (120 μm thick) was produced in the same manner as in Example 1, except that the LDPE (1) was used instead of the PETG, the EVA was used instead of the LDPE (1), the 6Ny was used instead of the EVOH, the modified PE (1) was used instead of the modified PE (2), and the conditions for co-extrusion of the resins were changed. A sealant layer (30 μm thick), a conforming layer (29 μm thick), a first adhesive layer (7 μm thick), a pinhole-resistant layer (5 μm thick), a gas barrier layer (5 μm thick), a second adhesive layer (14 μm thick), and an outer layer (30 μm thick) were laminated in this order in the thickness direction. This multilayer film was then evaluated in the same manner as in Example 1. The results are shown in Table 2. Next, a skin pack package was produced and evaluated in the same manner as in Example 1, except that this multilayer film was used as the lid material (sometimes referred to as "lid material (IX)" in this specification) instead of the lid material (I). The results are shown in Table 5.

[0249] Comparative Example 2 A zinc-based ionomer (ION, "Himilan (registered trademark) 1652" manufactured by Mitsui Dow Polychemicals) was prepared as a resin for forming the follow-up layer. In this specification, this ION may be referred to as "ION (3)". A multilayer film (thickness 120 μm) was produced by laminating a sealant layer (thickness 12 μm), a follow-up layer (thickness 17 μm), a first adhesive layer (thickness 6 μm), a pinhole-resistant layer (thickness 20 μm), a gas barrier layer (thickness 12 μm), a second adhesive layer (thickness 8 μm), and an outer layer (thickness 45 μm) in this order in the thickness direction in the same manner as in Example 1, except that ION (3) was used instead of ION (1). This multilayer film was then evaluated in the same manner as in Example 1. The results are shown in Table 3. Next, a skin pack package was produced and evaluated in the same manner as in Example 1, except that this multilayer film was used as the lid material (sometimes referred to as "lid material (X)" in this specification) instead of the lid material (I). The results are shown in Table 5. In this comparative example, damage to the lid material (lid material (X)) was found during the production of the skin pack packaging, as shown in Table 5. Therefore, in this comparative example, the presence or absence of discoloration of the contents after storage was not confirmed.

[0250] Comparative Example 3 A zinc-based ionomer (ION, "Himilan (registered trademark) 1554W" manufactured by Mitsui Dow Polychemicals) was prepared as a resin for forming the follow-up layer. In this specification, this ION may be referred to as "ION (4)". A multilayer film (thickness 120 μm) was produced by laminating a sealant layer (thickness 12 μm), a follow-up layer (thickness 17 μm), a first adhesive layer (thickness 6 μm), a pinhole-resistant layer (thickness 20 μm), a gas barrier layer (thickness 12 μm), a second adhesive layer (thickness 8 μm), and an outer layer (thickness 45 μm) in this order in the thickness direction in the same manner as in Example 1, except that ION (4) was used instead of ION (1). This multilayer film was then evaluated in the same manner as in Example 1. The results are shown in Table 3. In this comparative example, as shown in Table 3, the spreading properties of the conforming layer were poor, and the multilayer film (sometimes referred to in this specification as "lid material (XI)") could not be produced normally. Therefore, in this comparative example, a skin pack packaging body was not produced.

[0251] Comparative Example 4 A multilayer film (thickness 120 μm) was produced in the same manner as in Example 1, except that the conditions for co-extrusion of the resins were changed. The multilayer film was constructed by laminating a sealant layer (thickness 22 μm), a follow-up layer (thickness 17 μm), a first adhesive layer (thickness 6 μm), a pinhole-resistant layer (thickness 20 μm), a gas barrier layer (thickness 2 μm), a second adhesive layer (thickness 8 μm), and an outer layer (thickness 45 μm) in this order in the thickness direction. The multilayer film was then evaluated in the same manner as in Example 1. The results are shown in Table 3. Next, a skin pack package was produced and evaluated in the same manner as in Example 1, except that this multilayer film was used as the lid material (sometimes referred to as "lid material (XII)" in this specification) instead of the lid material (I). The results are shown in Table 5.

[0252] Comparative Example 5 A multilayer film (thickness 120 μm) was produced in the same manner as in Example 1, except that the conditions for co-extrusion of the resins were changed. The multilayer film was constructed by laminating a sealant layer (thickness 7 μm), a follow-up layer (thickness 17 μm), a first adhesive layer (thickness 6 μm), a pinhole-resistant layer (thickness 10 μm), a gas barrier layer (thickness 31 μm), a second adhesive layer (thickness 8 μm), and an outer layer (thickness 41 μm) in this order in the thickness direction. The multilayer film was then evaluated in the same manner as in Example 1. The results are shown in Table 3. Next, a skin pack package was produced and evaluated in the same manner as in Example 1, except that this multilayer film was used as the lid material (sometimes referred to as "lid material (XIII)" in this specification) instead of the lid material (I). The results are shown in Table 5.

[0253] [Table 1]

[0254] [Table 2]

[0255] [Table 3]

[0256] [Table 4]

[0257] [Table 5]

[0258] As is clear from the above results, in Examples 1 to 8, the oxygen permeability of the lid materials (lid materials (I) to (VIII), in other words, the multilayer films) was 10 cc / (m 2 ·day · atm) or less (0.3~10cc / (m 2·day·atm), and the lid material had high oxygen barrier properties. Reflecting this, in the skin pack packages of Examples 1 to 8, discoloration of the contents was suppressed.

[0259] Furthermore, the lid material had good conformability to the contents in the skin pack packages of Examples 1 to 8. In Examples 1 to 8, the ratio of the thickness of the gas barrier layer to the thickness of the lid material was 4.2 to 20%.

[0260] Furthermore, breakage of the lid material due to contact with the contents was suppressed in the skin pack packages of Examples 1 to 8. In the lid materials of Examples 1 to 8, the melt strength (180°C) of the ION was 200 to 400 mN.

[0261] In the skin pack packaging of Example 7, deformation of the base material was observed, but this was not observed in the skin pack packaging of Examples 1 to 6 and 8, and they had better properties. In the lid material of Example 7, the sealant layer was made of the HDPE, but in the lid materials of Examples 1 to 6 and 8, the sealant layer was made of the LDPE (1) or EVA, and the follow-up layer was made of the ION (1) or ION (2).

[0262] In the skin pack packaging of Example 8, thinning was observed in part of the lid material, but this was not observed in the skin pack packaging of Examples 1 to 7, which had better properties. In Example 8, the ratio of the pinhole-resistant layer thickness to the lid material thickness was 4.2%, but in Examples 1 to 7, the ratio of the pinhole-resistant layer thickness to the lid material thickness was 16.7% or more (16.7 to 25%).

[0263] In Examples 1 to 8, the multilayer film (lid material) had good spreading properties of the conforming layer. In the skin pack packages of Examples 1 to 8, as described above, the melt strength (180°C) of the ION was 200 to 400 mN, and the E' (140°C) of the lid material was 1.0 × 10 7 ~1.8×10 10 It was Pa.

[0264] As described above, all of the skin pack packages of Examples 1 to 8 had good properties, and among them, the skin pack packages of Examples 1 to 6 and 8 had even better properties, and the skin pack packages of Examples 1 to 6 had particularly good properties.

[0265] In contrast, the skin pack packaging of Comparative Example 1 did not prevent discoloration of the contents. In Comparative Example 1, the oxygen permeability of the lid material (IX) was 120 cc / (m 2 ·day·atm), which is consistent with the fact that the oxygen barrier property of the lid material (IX) was low and discoloration of the contents was not suppressed.

[0266] In the skin pack package of Comparative Example 2, damage to the lid material (X) due to contact with the contents was observed. In the lid material (X) of Comparative Example 2, the melt strength (180°C) of the ION (3) was low at 50 mN.

[0267] In Comparative Example 3, as explained above, the spreading property of the follow-up layer in the multilayer film (lid material (XI)) was poor. This was because the melt strength (180°C) of the ION (4) in Comparative Example 3 was high, at 550 mN. As a result, the E' (140°C) of the lid material (XI) was 5.9 × 10 10 Pa, and it was quite expensive.

[0268] In the skin pack packaging of Comparative Example 4, discoloration of the contents was not suppressed. In the multilayer film (lid material (XII)) of Comparative Example 4, the thickness ratio of the gas barrier layer was 1.7%, which was too small, resulting in so-called "layer breaks" where the gas barrier layer was not formed in part of the multilayer film, and this was presumed to be the cause of discoloration of the contents. In Comparative Example 4, the oxygen permeation rate of the lid material (XII) was low, but this was presumed to be due to the fact that the oxygen permeation rate was measured by chance in an area where the influence of layer breaks in the lid material (XIII) was unlikely to be reflected.

[0269] In the skin pack packaging of Comparative Example 5, the lid material (XIII) had poor conformability to the contents, and further, deformation of the base material was observed. This was presumably because the thickness ratio of the gas barrier layer in the lid material (XIII) of Comparative Example 5 was 25.8%, which was too large, resulting in the occurrence of problems with the lid material having a gas barrier layer. In Comparative Example 5, E' (140°C) was 2.2 × 10 11 Pa and was high. [Industrial Applicability]

[0270] The present invention can be used as a package, and is particularly suitable as a skin pack package, and is particularly suitable as a skin pack package for packaging hard and deformable contents such as frozen foods. [Explanation of symbols]

[0271] 1. Multilayer film (lid material) 11. Sealant layer 12. Follower layer 13. Gas barrier layer 10...Packaging 8...Bottom material T1: Thickness of multilayer film T 11 ...sealant layer thickness T 12 Thickness of the follow-up layer T 13 Gas barrier layer thickness

Claims

1. A multilayer film, The multilayer film is configured by laminating a sealant layer, a conforming layer, a gas barrier layer, and an outer layer in this order in a thickness direction, the compliant layer comprises an ionomer; the outer layer comprises one or more materials selected from the group consisting of low-density polyethylene, glycol-modified polyethylene terephthalate, and 6-nylon; a ratio of the total content of the low-density polyethylene, glycol-modified polyethylene terephthalate, and 6-nylon in the outer layer to the total mass of the outer layer is 70 to 100% by mass, The sealant layer has a density of 0.91 g / cm ３ Above, 0.93g / cm ３ containing less than 1000 ppm of low density polyethylene, the melt tension of the ionomer, measured in accordance with JIS K 7199 at a temperature of 180°C and a winding speed of 15 m / min, is 100 to 500 mN; the ratio of the thickness of the gas barrier layer to the thickness of the multilayer film is 5 to 25%; the sealant layer and the conformal layer are adjacent to each other; The thickness of the multilayer film is 80 to 200 μm, The oxygen permeability of the multilayer film measured in accordance with JIS K 7126-2:2006 under conditions of a temperature of 23°C and a relative humidity of 60% is 100 cc / (m ２ A multilayer film having a viscosity of 1000 psi (1000 psi) or less.

2. 2. The multilayer film according to claim 1, wherein the ratio of the thickness of the sealant layer to the thickness of the multilayer film is 5% or more.

3. 3. The multilayer film according to claim 1, wherein the ratio of the thickness of the conformal layer to the thickness of the multilayer film is 5% or more.

4. The multilayer film according to any one of claims 1 to 3, wherein the gas barrier layer comprises an ethylene-vinyl alcohol copolymer.

5. A packaging body comprising the multilayer film according to any one of claims 1 to 4.

6. 6. The package of claim 5, wherein the package is a skin pack package.

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