Multilayer film. package, and production method of package

Abstract

To provide: a multilayer film which maintains quality of a stored object, has excellent followability to the stored object, and is capable of softly following the stored object; and a package using the same (for example, a skin pack package).SOLUTION: Provided is a multilayer film which is configured by laminating a sealant layer, a following layer and a flexible layer in the thickness direction, in which the ratio of the thickness of the flexible layer to that of the multilayer film is 15-30%, the tensile strength of the multilayer film at a temperature of 140°C is 2 N / mm2 or more and 3.6 N / mm2 or less as measured in accordance with JIS K 7127:1999, the oxygen permeation amount of the multilayer film is more than 100 cc / (m2.day.atm) at a temperature of 23°C under a relative humidity of 60%, as measured in accordance with JIS K 7126-2:2006. The multilayer film is further irradiated with an electron beam in a condition of absorption dose of 175-300 kGy.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a multilayer film, a package, and a method for making the package. [Background technology]

[0002] A package in which the contents (packaged items) are placed on a hard tray and the contents are sealed with a film by drawing a vacuum is called a skin pack. In a skin pack, the film, i.e., the film for the skin pack, is transparent, and the contents can be easily seen through it. In addition, the film for the skin pack is soft, and by drawing a vacuum in the storage section inside the skin pack, it is possible to make the film adhere to the contents without causing wrinkles (see, for example, Patent Document 1). Furthermore, since the skin pack is provided with a hard tray (base material), it is possible to display the contents upright without causing any misalignment. In view of these characteristics, skin packs are mainly used as packaging for food. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-222259 A Summary of the Invention [Problem to be solved by the invention]

[0004] For example, in the case of a skin pack package for food, a gas barrier layer may be provided on the multilayer film constituting the skin pack package in order to prevent oxidation deterioration of the food. However, for example, foods such as chicken contain anaerobic bacteria such as lactic acid bacteria, so if the barrier property of the gas barrier layer is too high, the growth of the anaerobic bacteria is not suppressed, and the carbon dioxide gas released by the anaerobic bacteria is trapped in the skin pack package, causing the putrid odor of the carbon dioxide gas to adhere to the food and deteriorate the taste of the food. In addition, foods such as chicken have a transparent pink color when fresh, but if the barrier property of the gas barrier layer is too high, oxygen is less likely to enter the skin pack package from the outside, causing the food to fade due to lack of oxygen.

[0005] Furthermore, because foods such as chicken generally tend to be irregular in shape, there is also the problem that the skin pack's ability to conform to the food (the ability to adhere to the food without creating wrinkles) is reduced. Furthermore, in order to improve marketability, there is a demand for skin packs to be able to adhere to soft contents without crushing them when conforming to them.

[0006] The present invention has been made in consideration of the above circumstances, and has an objective of providing a multilayer film that maintains the quality of the contents, has excellent conformability to the contents, and can softly conform to the contents, as well as a packaging body (e.g., a skin pack packaging body) using the same. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention employs the following configuration. [1] A multilayer film, comprising a sealant layer, a conforming layer, and a flexible layer laminated in a thickness direction, the ratio of the thickness of the flexible layer to the thickness of the multilayer film being 2 to 30%, and the tensile strength of the multilayer film at a temperature of 140°C measured in accordance with JIS K 7127:1999 being 0.2 N / mm 2 More than 3.6N / mm 2The 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 multi-layer film that is ultra-high performance (1.5-day-atm). [2] The dynamic elastic modulus E' of the multilayer film at a temperature of 140°C is 1 x 10 4 Pa or more 1×10 7 The multilayer film according to [1], wherein the elastic modulus is 0.001 Pa or less. [3] The multilayer film according to [1] or [2], wherein the temperature at which the multilayer film shows a displacement of 2000 μm during thermomechanical analysis is 120° C. or higher. [4] The multilayer film according to any one of [1] to [3], wherein the multilayer film has a gel fraction of 30% or more. [5] The multilayer film described in [3], wherein during the thermomechanical analysis of the multilayer film, the displacement at a temperature of 100°C is 500 μm or less. [6] The multilayer film according to any one of [1] to [5], which is irradiated with an electron beam at an absorbed dose of 13 to 300 kGy. [7] The multilayer film according to any one of [1] to [6], wherein the flexible layer contains a polyethylene-based resin. [8] The multilayer film according to any one of [1] to [7], wherein the ratio of the thickness of the compliant layer to the thickness of the multilayer film is 10% or more. [9] The multilayer film described in any one of [1] to [8], wherein the ratio of the thickness of the sealant layer to the thickness of the multilayer film is 5% or more.

[10] .The tensile strength of the multilayer film at a temperature of 140°C, measured in accordance with JIS K 7127:1999, is 0.2N / mm 2 More than 3N / mm 2 The multilayer film according to any one of [1] to [9], which is:

[11] A package comprising the multilayer film according to any one of [1] to

[10] .

[12] The package according to

[11] , which is a skin pack package.

[13] A method for producing a package in which a content is packaged with a lid material and a base material, the method comprising the steps of: placing the content on the base material; placing the lid material in an area on the base material that covers the content and its surroundings; and heating the lid material to 90 to 250°C while bringing the lid material into contact with the content and molding it to fit the content, and adhering the portion of the lid material in contact with the base material to the base material, thereby packaging the content with the lid material and the base material, wherein the lid material is made of a multilayer film described in any one of [1] to

[10] . Effect of the Invention

[0008] The multilayer film of the present invention is constructed by laminating a sealant layer, a conforming layer, and a flexible layer in a thickness direction thereof, the ratio of the thickness of the flexible layer to the thickness of the multilayer film is 2 to 30%, and the tensile strength of the multilayer film at a temperature of 140°C measured in accordance with JIS K 7127:1999 is 0.2 N / mm 2 More than 3.6N / mm 2 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 It has a viscosity of over 10 ...

[0009] Furthermore, since the packaging body of the present invention includes the above multilayer film, it maintains the quality of the contents, has excellent conformability to the contents, and is capable of softly conforming to the contents. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view illustrating an example of a multilayer film according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a cross-sectional view showing a schematic example of a packaging body according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] <<Multilayer film (covering material)>> The multilayer film (lid material) according to one embodiment of the present invention is composed of a sealant layer, a conforming layer, and a flexible layer laminated in the thickness direction. The multilayer film (lid material) is not particularly limited as long as it satisfies the conditions of the thickness ratio of the flexible layer, the tensile strength, and the oxygen permeability described below.

[0012] The oxygen permeability of the multilayer film (covering material) under conditions of a temperature of 23°C and a relative humidity of 60% is 100 cc / (m 2 ·day·atm) (Oxygen permeability of multi-layer film > 100cc / (m 2 ·day·atm)). The oxygen permeation amount is 100cc / (m 2 By exceeding the standard of 100% (100% storage capacity), the quality of the contents can be maintained.

[0013] The oxygen permeability of the multilayer film (covering material) under conditions of a temperature of 23°C and a relative humidity of 60% is 110cc / (m 2 ·day·atm) or more, and 120cc / (m 2 ·day·atm) or more is preferable, and 130cc / (m 2 ·day·atm) or more, and 140cc / (m 2 ·day·atm) or more is particularly preferable, for example, 150cc / (m 2 When the oxygen transmission rate is equal to or more than the lower limit, the effect of maintaining the quality of the contents can be further improved.

[0014] On the other hand, the oxygen permeability is 5000cc / (m 2 ·day·atm) or less, and 4900cc / (m 2 ·day·atm) or less is more preferable, and 4800cc / (m 2 ·day·atm) or less, and 4700cc / (m2 ·day·atm) or less, for example, 4600cc / (m 2 When the oxygen transmission rate is equal to or less than the upper limit, excessive proliferation of aerobic bacteria inside the pack can be suppressed.

[0015] The oxygen transmission rate of the multilayer film (covering material) under conditions of a temperature of 23° C. and a relative humidity of 60% can be measured in accordance with JIS K 7126-2:2006.

[0016] The oxygen permeability of the multilayer film (covering material) can be more easily adjusted by, for example, adjusting the types and contents of the components contained in the flexible layer, which will be described later, the thickness of the flexible layer, the proportions thereof, and the like.

[0017] For example, in the case of a skin pack package for food, a gas barrier layer may be provided on the multilayer film constituting the skin pack package in order to prevent oxidation deterioration of the food. However, for example, foods such as chicken contain anaerobic bacteria such as lactic acid bacteria, so if the barrier property of the gas barrier layer is too high, the growth of the anaerobic bacteria is not suppressed, and the carbon dioxide gas released by the anaerobic bacteria is trapped in the skin pack package, causing the putrid odor of the carbon dioxide gas to adhere to the food and deteriorate the taste of the food. In addition, foods such as chicken have a transparent pink color when fresh, but if the barrier property of the gas barrier layer is too high, oxygen is less likely to enter the skin pack package from the outside, causing the food to fade due to lack of oxygen.

[0018] In contrast, such problems are improved in the case of a package constructed using the multilayer film 1 of the present embodiment. The reason is that the oxygen permeability of the multilayer film (covering material) under conditions of a temperature of 23° C. and a relative humidity of 60% is 100 cc / (m 2By having a humidity of more than 100% (100 / day·atm), the growth of anaerobic bacteria is inhibited, and furthermore, even if the anaerobic bacteria release carbon dioxide gas, the carbon dioxide gas is released to the outside of the skin pack packaging, and the putrid odor of the carbon dioxide gas is prevented from adhering to the food. In addition, oxygen can easily enter the skin pack packaging from the outside, and discoloration of food due to lack of oxygen can be prevented. In this way, a package constructed using the multilayer film 1 of this embodiment can maintain the quality of the contents.

[0019] The temperature at which the multilayer film (covering material) exhibits a displacement of 2000 μm during thermomechanical analysis (TMA) is preferably 120° C. or higher, more preferably 120 to 200° C., and even more preferably 123 to 190° C., and may be, for example, 130 to 190° C. When the temperature is equal to or higher than the lower limit, the heat resistance of the multilayer film is further improved. When the temperature is equal to or lower than the upper limit, the heat resistance of the multilayer film is further prevented from becoming excessive.

[0020] In thermomechanical analysis of the multilayer film, the displacement at a temperature of 100°C is preferably 500 μm or less, more preferably 40 to 500 μm, and even more preferably 45 to 400 μm, and may be, for example, any one of 50 to 350 μm, 55 to 340 μm, and 55 to 250 μm. When the displacement is equal to or less than the upper limit, the melt tension of the multilayer film is further improved, and as a result, the ability of the multilayer film to conform to the contents is further improved. When the displacement is equal to or more than the lower limit, the melt tension of the multilayer film is further prevented from becoming excessive.

[0021] The thermomechanical analysis of the multilayer film can be performed in accordance with JIS K 7196 by measuring the amount of thermal expansion of the sample from the difference in the amount of thermal expansion when a standard sample and a sample to be analyzed are heated at a constant rate. Thermomechanical analysis of a multilayer film can be performed, for example, by using a sample having a width of 40 mm, a length of 150 mm, and a thickness of 120 μm and measuring the displacement (amount of thermal expansion) of this sample in the machine direction (MD) of the film.

[0022] In the thermomechanical analysis of the multilayer film, the temperature at which the film shows a displacement of 2000 μm and the displacement at a temperature of 100° C. can be adjusted, for example, by irradiating the multilayer film with an electron beam and adjusting the conditions of the electron beam irradiation. For example, the temperature and displacement can be adjusted more easily by adjusting the conditions of the electron beam irradiation on the outer layer, the follow-up layer, and the soft layer in the multilayer film.

[0023] The multilayer film is preferably irradiated with an electron beam under an absorbed dose of 13 to 300 kGy, more preferably irradiated with an absorbed dose of 15 to 250 kGy, and may be irradiated with an electron beam under any of absorbed doses of 20 to 250 kGy, 45 to 250 kGy, and 70 to 250 kGy. When the absorbed dose is within such a range, the multilayer film can be more easily obtained in which the temperature at which the multilayer film shows a displacement of 2000 μm and the displacement at a temperature of 100° C. are both within the above-mentioned numerical ranges during thermomechanical analysis of the multilayer film. On the other hand, when the absorbed dose is equal to or greater than the lower limit, the crosslink density of the multilayer film (particularly the outer layer, the follower layer, and the soft layer in the multilayer film) is further improved, and as a result, the heat resistance and melt tension of the multilayer film as a whole are further improved, and the follower ability to the contents is further improved. When the absorbed dose is equal to or less than the upper limit, the strength of the multilayer film is more suppressed from becoming excessive.

[0024] The reason why the crosslink density of the multilayer film (particularly the outer layer, the follower layer and the flexible layer in the multilayer film) is improved by electron beam irradiation is not clear, but it is speculated as follows. That is, when the multilayer film is irradiated with an electron beam, the carbon-hydrogen bonds in the resin (e.g., polyethylene, ionomer) are broken, and radicals are generated at the ends of the broken bonds. It is speculated that the generated radicals come into contact with molecular chains of other resins (e.g., other polyethylene molecular chains, other ionomer molecular chains) due to the molecular motion of the molecular chains, abstract hydrogen atoms, and bond to carbon atoms in the molecular chains of other resins (e.g., other polyethylene molecular chains, other ionomer molecular chains), resulting in the formation of a crosslinked structure.

[0025] The accelerating voltage during electron beam irradiation is preferably 100 to 300 kV, more preferably 120 to 280 kV, and even more preferably 140 to 260 kV. By setting the accelerating voltage during electron beam irradiation within such a range, the multilayer film can be more easily obtained in which the temperature at which the multilayer film shows a displacement of 2000 μm and the displacement at a temperature of 100° C. are both within the above-mentioned numerical ranges during thermomechanical analysis of the multilayer film. On the other hand, by setting the accelerating voltage during electron beam irradiation to the lower limit or more, the crosslink density of the multilayer film (particularly the outer layer, the follower layer, and the soft layer in the multilayer film) is further improved, and as a result, the heat resistance and melt tension of the multilayer film as a whole are further improved, and the follower ability to the contents is further improved. By setting the accelerating voltage during electron beam irradiation to the upper limit or less, the strength of the multilayer film is more suppressed from becoming excessive.

[0026] The gel fraction of the multilayer film is preferably 30% or more, more preferably 30 to 90%, and even more preferably 32 to 85%, and may be, for example, any one of 40 to 82%, 48 to 82%, and 55 to 82%. When the gel fraction of the multilayer film is equal to or more than the lower limit, the heat resistance and melt tension of the multilayer film are further improved, and as a result, the conformability to the contents is further improved. When the gel fraction of the multilayer film is equal to or less than the upper limit, the strength of the multilayer film is further prevented from becoming excessive.

[0027] The gel fraction of the multilayer film can be measured in accordance with JIS K 6769, taking advantage of the fact that the crosslinked portion of the film does not dissolve in the solvent. That is, the multilayer film is immersed in an organic solvent such as xylene, and the insoluble film that remains undissolved is dried. The mass of the resulting dried product is then measured, and the gel fraction can be calculated from the mass of the multilayer film before dissolution and the mass of the dried product of the insoluble film. More specifically, for example, the multilayer film (mass Xg) is wrapped in a stainless steel wire net (mass Yg) and immersed in a heated solvent, and then the multilayer film wrapped in the stainless steel wire net (in other words, the insoluble film) is taken out. Next, it is vacuum dried, and the mass (Zg) of the multilayer film wrapped in the stainless steel wire net after drying (in other words, the insoluble film) is measured. Then, the following formula (1): Gel fraction of multilayer film (mass%) = (ZY) / X × 100 (1) The gel fraction of the multilayer film is calculated by the above formula.

[0028] The gel fraction of the multilayer film can be adjusted, for example, by irradiating the multilayer film (particularly the outer layer, the follower layer and the soft layer in the multilayer film) with an electron beam and adjusting the conditions of the electron beam irradiation. In this case, the conditions of the electron beam irradiation can be the same absorbed dose and the acceleration voltage of the electron beam irradiation as those used to adjust the temperature showing a displacement of 2000 μm and the displacement at a temperature of 100° C. in the thermomechanical analysis of the multilayer film described above.

[0029] The multilayer film preferably satisfies either one of the conditions of the temperature at which the film shows a displacement of 2000 μm during thermomechanical analysis and the gel fraction, or both of these conditions. That is, examples of the multilayer film include a film having a temperature at which the film shows a displacement of 2000 μm during thermomechanical analysis of 120° C. or higher and a gel fraction of less than 30%; a film having a temperature at which the film shows a displacement of 2000 μm during thermomechanical analysis of less than 120° C. and a gel fraction of 30% or higher; and a film having a temperature at which the film shows a displacement of 2000 μm during thermomechanical analysis of 120° C. or higher and a gel fraction of 30% or higher. However, it is usually more preferable that the multilayer film satisfies both of the above conditions, i.e., the temperature at which it shows a displacement of 2000 μm during thermomechanical analysis is 120° C. or higher and the gel fraction is 30% or higher.

[0030] The tensile strength of the multilayer film (lid material) at a temperature of 140°C is 0.2 N / mm 2 More than 3.6N / mm 2 The tensile strength is 0.2 N / mm 2 By satisfying the above, it is possible to improve the conformability of the lid material to the contents. As a result, dripping that occurs during storage is suppressed, preventing the outflow of umami components, and enabling long-term storage without deterioration of taste. 2 By satisfying the above, packaging can be performed without compressing the shape of the contents.

[0031] The tensile strength of the multilayer film (lid material) at a temperature of 140°C is 0.2 N / mm 2 More than 3N / mm 2 It is preferable that the resistance is less than 0.2N / mm 2 More than 2.9N / mm 2 More preferably, it is 0.2N / mm 2 More than 2.8N / mm 2 More preferably, it is equal to or less than 0.2 N / mm 2 More than 2.7N / mm 2When the tensile strength is equal to or greater than the lower limit, the ability of the lid material to conform to the contents can be improved. When the tensile strength is equal to or less than the upper limit, the contents can be packaged without compressing their shape.

[0032] The tensile strength of the multilayer film (covering material) at a temperature of 140° C. can be measured in accordance with JIS K 7127:1999. Specifically, it can be measured using a tensile strength measuring device ("Constant Temperature Chamber Tensile Tester AGS-X" manufactured by Shimadzu Corporation). The measurement conditions are, for example, a tensile speed of 500 mm / min.

[0033] When the crosslink density of the multilayer film (lid material) is improved, the heat resistance and melt tension of the multilayer film (lid material) are improved, and the tensile strength is also improved. Therefore, the tensile strength of the multilayer film (lid material) can be more easily adjusted by adjusting, for example, the absorbed dose of electron beam irradiation.

[0034] The tensile strength of the multilayer film (covering material) can be more easily adjusted by adjusting the thickness and ratio of the soft layer.

[0035] The dynamic elastic modulus E' of the multilayer film (covering material) at a temperature of 140°C is 1 x 10 4 Pa or more 1×10 7 It is preferable that the dynamic elastic modulus E' is equal to or less than the lower limit. When the dynamic elastic modulus E' is equal to or more than the upper limit, the ability of the lid material to conform to the contents can be improved. When the dynamic elastic modulus E' is equal to or less than the upper limit, the contents can be packaged without compressing their shape.

[0036] The dynamic elastic modulus E' of the multilayer film (covering material) at a temperature of 140°C is 1.1 x 10 4 Pa or more 9.9×10 6 Pa or less, and more preferably 1.2×10 4 Pa or more 9.8×10 6 More preferably, the pressure is 1.3×10 Pa or less. 4Pa or more 9.7×10 6 It is particularly preferable that the pressure is 1.4×10 Pa or less. 4 Pa or more 9.6×10 6 The dynamic elastic modulus E' may be equal to or less than the lower limit. When the dynamic elastic modulus E' is equal to or more than the upper limit, the ability of the lid material to conform to the contents can be improved. When the dynamic elastic modulus E' is equal to or less than the upper limit, the contents can be packaged without compressing their shape.

[0037] The dynamic elastic modulus E' of the multilayer film (covering material) at a temperature of 140°C can be measured in accordance with JIS K7244-4. Specifically, for example, it can be measured using a dynamic viscoelasticity measuring device ("DMA 7100" manufactured by Hitachi High-Tech Science Corporation). The measurement conditions are, for example, using a sample with a width of 4 mm in a tensile mode in a temperature range of 25°C to 160°C, a displacement of 10 μm, a vibration frequency of 1 Hz, and a temperature rise rate of 3°C / min.

[0038] When the crosslink density of the multilayer film (lid material) is improved, the heat resistance and melt tension of the multilayer film (lid material) are improved, and the dynamic modulus of elasticity E' is also improved. Therefore, the dynamic modulus of elasticity E' of the multilayer film (lid material) can be more easily adjusted, for example, by adjusting the absorbed dose of electron beam irradiation.

[0039] The dynamic elastic modulus E' of the multilayer film (covering material) can be more easily adjusted by adjusting the thickness and proportion of the soft layer.

[0040] The thickness of the multilayer film (covering material) 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 more 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 thickness of the multilayer film is further prevented from becoming excessive.

[0041] The multilayer film (lid material) is configured by laminating a sealant layer, a conforming layer, and a soft layer in the thickness direction. The multilayer film (lid material) is preferably configured by laminating a sealant layer, a conforming layer, and a soft layer in this order in the thickness direction.

[0042] In the multilayer film (lid material), all layers have transparency regardless of the type, that is, the multilayer film has transparency, that is, the multilayer film is preferably a transparent multilayer film. In a package formed using such a multilayer film, the contents can be easily visually confirmed through the multilayer film (lid material).

[0043] The detailed structure of the multilayer film (covering material) and the manufacturing method thereof will be described separately.

[0044] The present invention will be described in more detail below with reference to the drawings. Note that the drawings used in the following description may show essential parts in an enlarged scale for the sake of convenience in order to make the features of the present invention easier to understand, and the dimensional ratios of each component may not necessarily be the same as in reality.

[0045] FIG. 1 is a cross-sectional view that illustrates a schematic example of the multilayer film (laminate film) among the multilayer films (covering materials) in the present embodiment. The multilayer film 1 shown here is constructed by laminating a sealant layer 11, a conforming layer 13 (more specifically, a first conforming layer 131), and a soft layer 14 in this order in the thickness direction.

[0046] Additionally, the multilayer film 1 includes an outer layer 12 disposed on the side of the flexible layer 14 opposite the sealant layer 11 side. Additionally, multilayer film 1 includes a compliant layer 13 (more specifically, a second compliant layer 132 ) disposed between flexible layer 14 and outer layer 12 . Furthermore, the multilayer film 1 has an adhesive layer 15 (more specifically, a first adhesive layer 151) arranged between the first compliance layer 131 and the flexible layer 14, and an adhesive layer 15 (more specifically, a second adhesive layer 152) arranged between the flexible layer 14 and the second compliance layer 132. That is, the multilayer film 1 is constructed by laminating a sealant layer 11, a first conforming layer 131, a first adhesive layer 151, a flexible layer 14, a second adhesive layer 152, a second conforming layer 132 and an outer layer 12 in this order in the thickness direction. In the multilayer film 1, the outer layer 12 is the outermost layer on one side, and the sealant layer 11 is the outermost layer on the other side.

[0047] <Sealant layer> The sealant layer 11 may contain a polyethylene-based resin such as ethylene-vinyl acetate copolymer (EVA), polyethylene, ionomer, or polyethylene-based copolymer (sometimes referred to herein as a "polyethylene-based resin in the sealant layer"). When the sealant layer 11 contains a polyethylene-based resin in the sealant layer, the easy peelability of the multilayer film 1 is improved by exhibiting pseudo-adhesion to the adherend.

[0048] 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.

[0049] The sealant layer 11 may contain only a polyethylene-based resin in the sealant layer (i.e., the sealant layer may consist of a polyethylene-based resin), or may contain a polyethylene-based resin and other components (sometimes referred to as "other components" in this specification) in the sealant layer (i.e., the sealant layer may consist of a polyethylene-based resin and the other components).

[0050] The other components contained in the sealant layer 11 are not particularly limited and can be arbitrarily selected 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 polyethylene-based resin in the sealant layer. 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.

[0051] Examples of the other components that are 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 absorbing agents, and ultraviolet absorbing agents.

[0052] The other components contained in the sealant layer 11 may be one type only, or two or more types. When there are two or more types, the combination and ratio thereof can be arbitrarily selected depending on the purpose.

[0053] The content of the polyethylene resin in the sealant layer 11 relative to the total mass of the sealant layer 11 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 more than the lower limit, the easy peel property due to the expression of pseudo-adhesion to the adherend is further improved. The ratio is usually the same as the ratio of the content (parts by mass) of the polyethylene resin in the sealant layer to the total content (parts by mass) of components that do not vaporize at room temperature in the composition for forming a sealant layer described below.

[0054] In this specification, "room temperature" means a temperature that is neither particularly cooled nor heated, that is, an ordinary temperature, and examples thereof include temperatures of 15 to 25°C.

[0055] The sealant layer 11 may be composed of one layer (single layer) or may be composed of two or more layers. When the sealant layer 11 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.

[0056] In this specification, not only in the case of the sealant layer 11, "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".

[0057] The thickness of the sealant layer 11 is not particularly limited, but is preferably 4 to 96 μm, more preferably 7 to 93 μm, and further preferably 10 to 90 μm, and may be, for example, any one of 10 to 70 μm, 10 to 50 μm, and 10 to 30 μm. When the thickness of the sealant layer 11 is equal to or greater than the lower limit, the strength of the sealant layer 11 is increased. When the thickness of the sealant layer 11 is equal to or less than the upper limit, the sealant layer 11 is prevented from becoming excessively thick, and the seal strength is increased when the multilayer film 1 is sealed by heating. Here, "the thickness of sealant layer 11" means the thickness of the entire sealant layer 11, and for example, the thickness of sealant layer 11 consisting of multiple layers means the total thickness of all layers that make up sealant layer 11.

[0058] The ratio of the thickness of the sealant layer 11 to the thickness of the multilayer film 1 is not particularly limited, but is preferably 5% or more, more preferably 6 to 80%, and even more preferably 7 to 75%. When the ratio is equal to or more than the lower limit, the effect obtained by externally irradiating the multilayer film 1 with an electron beam from the outer layer 12 side is enhanced. When the ratio is equal to or less than the upper limit, the sealant layer 11 is prevented from becoming excessively thick, and the seal strength is increased when the multilayer film 1 is sealed by heating.

[0059] When the sealant layer is made of ethylene-vinyl acetate copolymer (EVA) or contains ethylene-vinyl acetate copolymer (EVA) as the main component, by making the thickness of the sealant layer thicker, it can also function as a follow-up layer.

[0060] An exposed surface 11a of the sealant layer 11 opposite to the outer layer 12 (sometimes referred to as the "first surface" in this specification) is a sealing surface.

[0061] <Outer layer> The outer layer 12 may contain a polyolefin resin such as polyethylene (PE) or ethylene-vinyl acetate copolymer (EVA), or a polyester resin such as polyethylene terephthalate resin (PET, PETG) (the polyolefin resin and the polyester resin may be referred to as "outer layer resin" in this specification). When the outer layer 12 contains an outer layer resin, the crosslink density of the outer layer 12 can be further improved when the multilayer film 1 is irradiated with an electron beam. As a result, the conformability of the multilayer film 1 to the contents contained therein is further improved.

[0062] The outer layer 12 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).

[0063] Examples of the resin contained in the outer layer 12 include low density polyethylene (LDPE), linear low density polyethylene (LLDPE), metallocene-catalyzed linear low density polyethylene (mLLDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), etc. Among these, low density polyethylene (LDPE) is preferable. Low density polyethylene has a density of, for example, 0.945 g / cm 3 It is preferable that the polyethylene used is a low density polyethylene having a density of 0.943 g / cm or less. 3 More preferably, the polyethylene has a density of 0.941 g / cm or less. 3 The following low density polyethylene is more preferable. By including such a low density polyethylene (LDPE), the crosslink density of the outer layer 12 can be further improved by irradiating the multilayer film 1 with an electron beam from the outside on the outer layer 12 side. As a result, the conformability of the multilayer film 1 to the contents inside can be further improved.

[0064] The resin contained in the outer layer 12 may be only one type, or may be two or more types. When there are two or more types, the combination and ratio thereof can be arbitrarily selected depending on the purpose.

[0065] The other components contained in the outer layer 12 are not particularly limited and can be arbitrarily selected 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 the resin in the outer layer.

[0066] The other components contained in the outer layer 12 may be one type only, or two or more types. When there are two or more types, the combination and ratio thereof can be arbitrarily selected depending on the purpose.

[0067] The proportion of the resin content in the outer layer 12 relative to the total mass of the outer layer 12 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 one of 70 to 100% by mass and 85 to 100% by mass. When the proportion is equal to or more than the lower limit, the crosslink density of the outer layer 12 can be further improved by irradiating the multilayer film 1 with an electron beam from the outside on the outer layer 12 side. As a result, the conformability of the multilayer film 1 to the contents contained therein is further improved. The above ratio is usually the same as the ratio of the content (parts by mass) of the resin in the outer layer 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.

[0068] The outer layer 12 may be composed of one layer (single layer) or may be composed of two or more layers. When the outer layer 12 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.

[0069] The thickness of the outer layer 12 is not particularly limited, but is preferably 4 to 146 μm, more preferably 7 to 143 μm, and further preferably 10 to 140 μm, and may be, for example, any one of 10 to 110 μm, 10 to 100 μm, 10 to 90 μm, 10 to 80 μm, and 10 to 70 μm. When the thickness of the outer layer 12 is equal to or more than the lower limit, the crosslink density of the outer layer 12 can be further improved by irradiating the multilayer film 1 with an electron beam from the outside on the outer layer 12 side. When the thickness of the outer layer 12 is equal to or less than the upper limit, the outer layer 12 is prevented from becoming excessively thick. Here, "the thickness of the outer layer 12" means the thickness of the entire outer layer 12. For example, the thickness of the outer layer 12 consisting of multiple layers means the total thickness of all layers that make up the outer layer 12.

[0070] The ratio of the thickness of the outer layer 12 to the thickness of the multilayer film 1 is not particularly limited, but is preferably 10% or more, more preferably 12 to 88%, and even more preferably 14 to 86%. When the ratio is equal to or more than the lower limit, the effect obtained by irradiating the multilayer film 1 with an electron beam from the outside on the outer layer 12 side is enhanced. When the ratio is equal to or less than the upper limit, the outer layer 12 is prevented from becoming excessively thick.

[0071] <Followers> The conforming layer 13 may contain a polyolefin resin such as an ionomer (ION) or an ethylene-vinyl acetate copolymer (EVA). Of these, it is preferable that the conforming layer 13 contains an ionomer. The ionomer means a copolymer of ethylene and a small amount of acrylic acid or methacrylic acid, which is ionically crosslinked by forming a salt between the acid portion and a metal ion.

[0072] 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.

[0073] In addition to the ionomer, the following layer 13 may contain a polyethylene-based resin such as ethylene-vinyl acetate copolymer (EVA), polyethylene, or a polyethylene-based copolymer (in this specification, the ionomer and the polyethylene-based resin may be referred to as the "polyethylene-based resin in the following layer"). When the following layer 13 contains a polyethylene-based resin in the following layer, the crosslink density of the following layer 13 can be improved when the multilayer film 1 is irradiated with an electron beam. As a result, the ability of the package formed using the multilayer film 1 to follow the contents is further improved.

[0074] The following layer 13 may be made of one layer (single layer) or may be made of two or more layers. When the following layer 13 is made 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.

[0075] In this embodiment, the follower layers 13 are provided at different positions on the multilayer film 1. In this embodiment, in order to distinguish these follower layers 13 from one another, the follower layer 13 disposed between the sealant layer 11 and the first adhesive layer 151 may be referred to as the first follower layer 131, and the follower layer 13 disposed between the second adhesive layer 152 and the outer layer 12 may be referred to as the second follower layer 132, as necessary. These compliant layers 13 (first compliant layer 131 and second compliant layer 132) may be the same as or different from each other.

[0076] The conforming layer 13 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).

[0077] The following layer 13 may contain only one type of ionomer, or may contain two or more types. When there are two or more types, the combination and ratio thereof can be arbitrarily selected depending on the purpose.

[0078] The other components contained in the follow-up layer 13 are not particularly limited and can be arbitrarily selected 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.

[0079] The other components contained in the follow-up layer 13 may be one type only, or two or more types. When there are two or more types, the combination and ratio thereof can be arbitrarily selected depending on the purpose.

[0080] The ratio of the ionomer content in the following layer 13 to the total mass of the following layer 13 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 one of 70 to 100% by mass and 85 to 100% by mass. When the ratio is equal to or more than the lower limit, the crosslink density of the following layer 13 can be further improved by irradiating the multilayer film 1 with an electron beam from the outside on the outer layer 12 side. As a result, the ability of the multilayer film 1 to follow the contents is further improved. The above 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 a follow-up layer, which will be described later.

[0081] The thickness of the following layer 13 (the thickness of each of the first following layer 131 and the second following layer 132) is preferably 4 to 146 μm, more preferably 7 to 143 μm, and further preferably 10 to 140 μm, and may be, for example, any one of 10 to 110 μm, 10 to 80 μm, 10 to 50 μm, and 10 to 30 μm. When the thickness of the following layer 13 is equal to or more than the lower limit, the crosslink density of the following layer 13 can be further improved by irradiating the multilayer film 1 with an electron beam from the outside on the outer layer 12 side. As a result, the following ability of the multilayer film 1 to the contents is further improved. When the thickness of the following layer 13 is equal to or less than the upper limit, the thickness of the following layer 13 is prevented from becoming excessive. Here, "the thickness of the following layer 13" means the overall thickness of the following layer 13 (for example, the overall thickness of the following layer 13 disposed between the sealant layer 11 and the first adhesive layer 151, or the overall thickness of the following layer 13 disposed between the second adhesive layer 152 and the outer layer 12), and for example, the thickness of the following layer 13 consisting of multiple layers means the total thickness of all layers constituting the following layer 13.

[0082] The ratio of the thickness of the follow-up layer 13 to the thickness of the multilayer film 1 is not particularly limited, but is preferably 10% or more, more preferably 11 to 89%, and even more preferably 12 to 88%. When the ratio is equal to or more than the lower limit, the effect obtained by irradiating the multilayer film 1 with an electron beam is enhanced. When the ratio is equal to or less than the upper limit, the follow-up layer 13 is prevented from becoming excessively thick.

[0083] When the following layer is made of an ionomer (ION) or contains an ionomer (ION) as a main component, by making the thickness of the following layer thicker, the following layer can also function as an outer layer.

[0084] <Flexible layer> The flexible layer 14 improves the flexibility of the multilayer film 1 and also improves the ability of the multilayer film 1 to conform to the contents contained therein.

[0085] Flexible layer 14 may contain a polyethylene resin such as polyethylene, ionomer, ethylene-vinyl acetate copolymer (EVA), ethylene-methacrylic acid copolymer (EMAA), ethylene methacrylate copolymer (EMMA), other polyethylene copolymers, or a polyamide resin such as nylon (sometimes referred to as "flexible layer resin" in this specification). By containing a flexible layer resin in flexible layer 14, the flexibility of multilayer film 1 is improved, and the crosslink density of flexible layer 14 can be further improved when multilayer film 1 is irradiated with an electron beam. As a result, the ability of multilayer film 1 to conform to the contents contained therein is further improved.

[0086] The resin in the flexible layer is preferably a resin other than ethylene-vinyl alcohol copolymer (EVOH, also known as saponified ethylene-vinyl acetate copolymer). By using such a resin in the flexible layer, the oxygen permeability of the multilayer film (covering material) under conditions of a temperature of 23° C. and a relative humidity of 60% can be increased to 100 cc / (m 2 ·day·atm) and it becomes easier to adjust to the maximum temperature.

[0087] The flexible layer 14 may contain only the resin in the flexible layer (i.e., it may consist of the resin in the flexible layer), or it may contain the resin in the flexible layer and other components (sometimes referred to as "other components" in this specification) (i.e., it may consist of the resin in the flexible layer and the other components).

[0088] The other components contained in flexible layer 14 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 components, which are resin components, are resins that do not fall under the category of resins in the flexible layer. 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.

[0089] 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 11.

[0090] The other components contained in flexible layer 14 may be only one type, or may be two or more types, and when there are two or more types, the combination and ratio thereof can be arbitrarily selected depending on the purpose.

[0091] The content of the resin in the flexible layer 14 relative to the total mass of the flexible layer 14 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 the content is equal to or greater than the lower limit, the flexibility of the multilayer film 1 is further improved, and the crosslink density of the flexible layer 14 can be further improved by irradiating the multilayer film 1 with an electron beam from the outside on the outer layer 12 side. As a result, the conformability of the multilayer film 1 to the contents contained therein is further improved. The ratio is usually the same as the ratio of the content (parts by mass) of the resin in the flexible layer to the total content (parts by mass) of components that do not vaporize at room temperature in the composition for forming the flexible layer described below.

[0092] The content of the ethylene-vinyl alcohol copolymer in the flexible layer 14 relative to the total mass of the flexible layer 14 is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 1% by mass or less, and may be, for example, 0% by mass (flexible layer 14 does not contain an ethylene-vinyl alcohol copolymer). When the content is equal to or less than the upper limit, the oxygen permeability of the multilayer film (covering material) becomes greater under conditions of a temperature of 23°C and a relative humidity of 60%. The ratio is usually the same as the ratio of the content (parts by mass) of the ethylene-vinyl alcohol copolymer to the total content (parts by mass) of components that do not vaporize at room temperature in the composition for forming a flexible layer described below.

[0093] The flexible layer 14 may be composed of one layer (single layer) or may be composed of two or more layers. When the flexible layer 14 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.

[0094] The thickness of the flexible layer 14 is preferably 1 to 100 μm, more preferably 1.5 to 90 μm, and further preferably 2 to 80 μm, and may be, for example, any one of 4 to 60 μm, 4 to 40 μm, and 4 to 20 μm. When the thickness of the flexible layer 14 is equal to or greater than the lower limit, the flexibility of the multilayer film 1 is further improved, and the crosslink density of the flexible layer 14 can be further improved by irradiating the multilayer film 1 with an electron beam from the outside on the outer layer 12 side. As a result, the ability of the multilayer film 1 to conform to the contents contained therein is further improved. When the thickness of the flexible layer 14 is equal to or less than the upper limit, the tensile strength of the multilayer film 1 at a temperature of 140° C. is 3.6 N / mm 2 or less, and the shape of the packaged contents can be better maintained. Here, "the thickness of flexible layer 14" means the thickness of the entire flexible layer 14; for example, the thickness of flexible layer 14 consisting of multiple layers means the total thickness of all layers that make up flexible layer 14.

[0095] The ratio of the thickness of the flexible layer 14 to the thickness of the multilayer film 1 is 2 to 30%. When the ratio is equal to or greater than the lower limit, it is possible to suppress breakage of the flexible layer. In this specification, "breakage of the flexible layer" means that the flexible layer is not partially formed in the multilayer film, which occurs, for example, when the flexible layer is too thin. When the ratio is equal to or less than the upper limit, it is possible to suppress the tensile strength of the multilayer film 1 at a temperature of 140°C to 3.6 N / mm 2 The above structure can be adopted, and the shape of the packaged contents can be maintained.

[0096] The ratio of the thickness of the flexible layer 14 to the thickness of the multilayer film 1 is more preferably 2.2 to 24.8%, and even more preferably 2.4 to 24.6%. When the ratio is equal to or greater than the lower limit, the flexible layer can be further prevented from being torn. When the ratio is equal to or less than the upper limit, the tensile strength of the multilayer film 1 at a temperature of 140°C can be reduced to 3.6 N / mm 2 or less, and the shape of the packaged contents can be better maintained.

[0097] For example, foods such as chicken meat generally have irregular shapes, which reduces the ability of the skin pack to conform to the food (to be able to adhere tightly without wrinkling).

[0098] In contrast, such problems are improved in a package constructed using the multilayer film 1 of the present embodiment, which has the outer layer 12, the conforming layer 13, and the flexible layer 14. The reason is that the heat resistance, melt tension, and tensile strength of the multilayer film 1 are improved due to the presence of the outer layer 12, the conforming layer 13, and the flexible layer 14, and as a result, the multilayer film 1 has excellent conformability to the contents.

[0099] <Adhesive layer> The adhesive layer 15 includes an adhesive. The adhesive layer 15 bonds two adjacent layers on both sides. In the multilayer film 1, the adhesive layer 15 disposed between the pinhole resistant layer 16 and the flexible layer 14 bonds the pinhole resistant layer 16 and the flexible layer 14, and the adhesive layer 15 disposed between the flexible layer 14 and the conforming layer 13 bonds the flexible layer 14 and the conforming layer 13. In this specification, in order to distinguish between these two adhesive layers 15, the adhesive layer 15 disposed between the pinhole resistant layer 16 and the flexible layer 14 may be referred to as a first adhesive layer 151, and the adhesive layer 15 disposed between the flexible layer 14 and the conforming layer 13 may be referred to as a second adhesive layer 152, as necessary. These two adhesive layers 15 (first adhesive layer 151 and second adhesive layer 152) may be the same as or different from each other.

[0100] The adhesive contained in adhesive layer 15 is not particularly limited as long as it can bond two layers to be bonded 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 types of olefin monomers).

[0101] More specifically, examples of the olefin-based resin contained in the adhesive layer 15 include ethylene-based copolymers, propylene-based copolymers, and butene-based copolymers. The ethylene-based copolymer is a copolymer of ethylene and a monomer other than ethylene. The propylene-based 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.

[0102] The ethylene copolymer contained in the adhesive layer 15 may be, for example, a copolymer of ethylene and a vinyl group-containing monomer. 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), ionomers (ION), and ethylene-based thermoplastic elastomers. The ionomer may be, for example, the same ionomer as that listed above as the ionomer contained in the follow-up layer 13 .

[0103] The propylene-based copolymer contained in the adhesive layer 15 may be, for example, a copolymer of propylene and a vinyl group-containing monomer. Examples of the copolymer of propylene and a vinyl group-containing monomer include linear low-density polypropylene grafted with maleic anhydride, and propylene-based thermoplastic elastomers.

[0104] Examples of the butene copolymer contained in the adhesive layer 15 include copolymers of 1-butene and vinyl group-containing monomers, copolymers of 2-butene and vinyl group-containing monomers, and modified products of these copolymers (modified copolymers).

[0105] The adhesive layer 15 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).

[0106] The adhesive layer 15 may contain only one type of adhesive, or two or more types. When there are two or more types, the combination and ratio thereof can be arbitrarily selected depending on the purpose.

[0107] The other components contained in the adhesive layer 15 are not particularly limited and can be arbitrarily selected depending on the purpose, and may be, for example, either a resin component or a non-resin component.

[0108] The other components contained in the adhesive layer 15 may be of only one type, or of two or more types. When there are two or more types, the combination and ratio thereof can be arbitrarily selected depending on the purpose.

[0109] The content of the adhesive in the adhesive layer 15 with respect to the total mass of the adhesive layer 15 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.

[0110] The adhesive layer 15 may be made of one layer (single layer) or may be made of two or more layers. When the adhesive layer 15 is made 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.

[0111] The thickness of the adhesive layer 15 (each of the first adhesive layer 151 and the second adhesive layer 152) is preferably 4 to 96 μm, more preferably 7 to 93 μm, and may be, for example, any one of 7 to 80 μm, 7 to 60 μm, 7 to 40 μm, and 7 to 20 μm. When the thickness of the adhesive layer 15 is equal to or greater than the lower limit, the adhesive strength of the two layers to be bonded is increased. When the thickness of the adhesive layer 15 is equal to or less than the upper limit, the adhesive layer 15 is prevented from becoming excessively thick. Here, "the thickness of adhesive layer 15" means the overall thickness of adhesive layer 15 (for example, the overall thickness of adhesive layer 15 arranged between pinhole-resistant layer 16 and flexible layer 14, the overall thickness of adhesive layer 15 arranged between flexible layer 14 and conformal layer 13), and for example, the thickness of adhesive layer 15 consisting of multiple layers means the total thickness of all layers constituting adhesive layer 15.

[0112] <Other layers> The multilayer film 1 may have other layers that do not fall into any of the sealant layer 11, outer layer 12, conforming layer 13, flexible layer 14, and adhesive layer 15, as long as the effects of the present invention are not impaired.

[0113] The type and arrangement of the other layer are not particularly limited and can be arbitrarily selected depending on the purpose.

[0114] The other layers included in the multilayer film 1 may be of only one type, or of two or more types. When there are two or more types, the combination and ratio thereof can be selected arbitrarily depending on the purpose.

[0115] The other layers may each be one layer (single layer) or two or more layers. When the other layers are multiple layers, the multiple layers may be the same or different from each other, and the combination of the multiple layers is not particularly limited as long as it does not impair the effects of the present invention.

[0116] The thickness of the other layer can be set arbitrarily depending on the type of the other layer, and is not particularly limited.

[0117] When the multilayer film 1 includes the other layers, it may further include an adhesive layer (eg, adhesive layer 15, etc.) for adhering the other layers to other layers.

[0118] The thickness of the multilayer film 1 is the same as the thickness of the multilayer film (covering material) described above.

[0119] The multilayer film in this embodiment is not limited to the above, and some of the configuration may be changed, deleted, or added without departing from the spirit of the present invention. For example, the multilayer film may not include one or both of the outer layer and the adhesive layer, but preferably includes a sealant layer, a conforming layer, an adhesive layer, a soft layer, an adhesive layer, a conforming layer, and an outer layer in this order, as shown in FIG.

[0120] <<Manufacturing method of multi-layer film (covering material)>> The multilayer film (covering material) can be produced by a known method depending on the type. For example, laminated films such as the multilayer films can be produced by a feed block method in which resins or resin compositions that are materials for forming each layer are melt-extruded using several extruders, a co-extrusion T-die method such as a multi-manifold method, or an air-cooled or water-cooled co-extrusion inflation method.

[0121] The laminate film can also be produced by coating a resin or resin composition, which is a material for forming one of the layers, on the surface of another layer that constitutes the laminate film, and drying it as necessary to form a laminate structure in the laminate film, and if necessary, further laminating other layers so as to obtain the desired arrangement.

[0122] The laminated film can also be produced by separately preparing two or more films for constituting any two or more of the layers, laminating the films together using an adhesive by any one of dry lamination, extrusion lamination, hot melt lamination and wet lamination, and further laminating other layers as necessary to obtain the desired arrangement. In this case, the adhesive used may be one capable of forming the adhesive layer.

[0123] The laminated film can also be produced by laminating two or more films, which have been prepared separately in advance, by a thermal lamination method or the like without using an adhesive, and, if necessary, further laminating other layers so as to achieve the desired arrangement.

[0124] When producing the laminated film, two or more of the methods for forming any of the layers (films) in the laminated film mentioned above may be combined.

[0125] Regardless of the manufacturing method, the resin composition that is the material for forming any layer in the laminated film may be manufactured by adjusting the type and content of the components contained so that the layer to be formed contains the desired components (constituent materials) in the desired content. For example, the content ratio of the components that do not vaporize at room temperature in the resin composition is usually the same as the content ratio of the components in the layer formed from this resin composition.

[0126] Examples of resin compositions (sometimes referred to in this specification as "sealant layer-forming compositions") for forming a sealant layer (sealant layer 11 in the multilayer film 1 shown in FIG. 1) include those that contain the polyethylene resin in the sealant layer and, if necessary, the other components described above.

[0127] Examples of the resin composition (sometimes referred to in this specification as an "outer layer forming composition") for forming the outer layer (outer layer 12 in the multilayer film 1 shown in FIG. 1) include those containing the resin in the outer layer and, if necessary, the other components described above.

[0128] Examples of the resin composition (sometimes referred to in this specification as a "composition for forming a following layer") for forming a following layer (following layer 13 in the multilayer film 1 shown in FIG. 1) include those containing the polyethylene resin in the following layer and, if necessary, the other components described above.

[0129] A resin composition (sometimes referred to in this specification as a "composition for forming a flexible layer") for forming a flexible layer (flexible layer 14 in the multilayer film 1 shown in Figure 1) may, for example, contain the resin in the flexible layer and, if necessary, the other components described above.

[0130] Examples of resin compositions (sometimes referred to in this specification as "adhesive layer-forming compositions") for forming an adhesive layer (adhesive layer 15 in the multilayer film 1 shown in Figure 1) include those containing the adhesive and, if necessary, the other components described above.

[0131] The multilayer film 1 can be used as a lid material. The packaging body of this embodiment can be produced by heat sealing this lid material and a base material.

[0132] <<Bottom material>> The base material has an oxygen permeability of 100cc / (m 2 There are no particular limitations as long as the material has a viscosity of more than 1.5 MPa (1.5 MPa), and is usable as a base material for a packaging body. The base material may be any known material.

[0133] The oxygen permeability of the base material under conditions of a temperature of 23°C and a relative humidity of 60% is 110cc / (m 2 ·day·atm) or more, for example, 130cc / (m 2 ·day · atm) or more, 120cc / (m 2 ·day · atm) or more, 140cc / (m 2 ·day · atm) or more, and 150cc / (m 2 ·day·atm) or higher. On the other hand, the oxygen permeability is 5000cc / (m 2 ·day·atm) or less, for example, 4900cc / (m 2 ·day · atm) or less, 4800cc / (m 2 ·day · atm) or less, 4700cc / (m 2 ·day·atm) or less, and 4600cc / (m 2 ·day·atm) or less.

[0134] The oxygen transmission rate of the base material under conditions of a temperature of 23° C. and a relative humidity of 60% can be measured in accordance with JIS K 7126-2:2006.

[0135] The oxygen permeability of the base material can be more easily adjusted by adjusting, for example, the types and contents of the components contained in the base material, the thickness of the base material, etc.

[0136] 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 more 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 making the thickness of the base material equal to or less than the upper limit, the thickness of the base material is prevented from becoming excessive. The thickness of the base material can be appropriately adjusted within a range set by any combination of any of the lower limit values ​​and upper limit values ​​described above.

[0137] Regardless of the type of base material, all layers may be transparent and the base material may be transparent, or all or some 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 viewed through the base material.

[0138] A more detailed configuration of the base material and its manufacturing method will be described separately.

[0139] <<One embodiment of the base material>> The base material is preferably a laminate formed by laminating a plurality of layers. A preferred example of the 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.

[0140] 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).

[0141] 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. The thickness of the foamed resin layer is not particularly limited, but is preferably 500 to 6000 μm.

[0142] The non-foamed resin layer may be, for example, a multi-layer film for a base material, which is constructed by laminating an easy-peel layer, a soft layer, a pinhole-resistant layer, and an adhesive layer in this order in the thickness direction, in which the easy-peel layer is the outermost layer on one side, and the adhesive layer is the outermost layer on the other side.

[0143] The multi-layer film for base materials may, for example, have an intermediate adhesive layer between the easy-peel layer and the soft layer for adhering these two layers. The multi-layer film for base materials may also include, for example, an intermediate adhesive layer between the soft layer and the pinhole resistant layer for bonding these two layers. That is, the multilayer film for base materials may be constructed by laminating an easy peel layer, an intermediate adhesive layer, a soft layer, an intermediate adhesive layer, a pinhole resistant layer, and an adhesive layer in this order in the thickness direction.

[0144] In this specification, in order to distinguish these two intermediate adhesive layers from each other, if necessary, the intermediate adhesive layer disposed between the easy peel layer and the flexible layer may be referred to as the first intermediate adhesive layer, and the intermediate adhesive layer disposed between the flexible layer and the pinhole resistant layer may be referred to as the second intermediate adhesive layer. These two intermediate adhesive layers (first intermediate adhesive layer, second intermediate adhesive layer) may be the same as or different from each other.

[0145] <Easy peel layer> The easy peel layer in the multi-layer film for base materials may be one that exhibits peelability due to cohesive failure. An example of an easy peel layer that exhibits peelability by cohesive failure is one that contains two incompatible polyolefins.

[0146] 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, for example, contain 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.

[0147] The ethylene-based polymer contained in the easy-peel layer in the multi-layer film for base material includes an ethylene homopolymer and an ethylene-based copolymer.

[0148] 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).

[0149] The ethylene-based copolymer has structural units derived from ethylene and structural units derived from a monomer other than ethylene. Examples of the ethylene-based copolymers 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 conforming layer 13 in the multilayer film 1 described above.

[0150] The easy peel layer in the multi-layer film for base material preferably contains a low density polyethylene as the ethylene polymer, which provides better easy peeling properties.

[0151] The propylene-based polymer contained in the easy peel layer in the multi-layer film for base materials includes a propylene homopolymer (that is, polypropylene or homopolypropylene, hPP) and a propylene-based copolymer.

[0152] The propylene-based copolymer has structural units derived from propylene and structural units derived from a monomer other than propylene. Examples of the propylene-based copolymer include propylene-ethylene random copolymer (also known as polypropylene random copolymer, rPP), and propylene-ethylene block copolymer (also known as polypropylene block copolymer, bPP).

[0153] The easy peel layer in the multi-layer film for base material preferably contains polypropylene as the propylene-based polymer, which provides better easy peeling properties.

[0154] The component exhibiting easy peelability contained in the easy peel layer in the multilayer film for base material may be only one type or may be two or more types, and when it is two or more types, the combination and ratio thereof can be arbitrarily selected according to the purpose. For example, when the component exhibiting easy peelability is the above-mentioned two incompatible polyolefins, each of these polyolefins contained in the easy peel layer may be only one type or may be two or more types.

[0155] In the easy peel layer in the base multilayer film, 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, any of 30 to 90% by mass, 45 to 90% by mass, and 60 to 90% by mass. When the ratio is equal to or more than the lower limit, the easy peel property of the easy peel layer becomes better. When the ratio is equal to or less than the upper limit, the peel strength becomes more stable. The above 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 described below.

[0156] 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 type only, or two or more types. When there are two or more types, the combination and ratio thereof can be arbitrarily selected depending on the purpose.

[0157] In the easy peel layer in the base multilayer film, the ratio of the content of the component exhibiting easy peel properties to the total mass of the easy peel layer (for example, the ratio of the total content of the above-mentioned two incompatible polyolefins) is preferably 50 to 100 mass%, more preferably 70 to 100 mass%, and may be, for example, any of 80 to 100 mass%, 90 to 100 mass%, 95 to 100 mass%, 97 to 100 mass%, and 99 to 100 mass%. When the ratio is equal to or more 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.

[0158] 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.

[0159] The easy peel layer in the multi-layer film for base material may be one layer (single layer) or two or more layers. When the easy peel layer is made 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.

[0160] The thickness of the easy peel layer in the multilayer film for base material 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 high. When the thickness of the easy peel layer is equal to or less than the upper limit, the easy peel property is further improved. Here, "the 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.

[0161] 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 high. When the ratio is equal to or less than the upper limit, the easy peel property is further improved.

[0162] <Flexible layer> The soft layer improves the flexibility of the multi-layer film for base materials.

[0163] The flexible layer in the multilayer film for base material may contain the resin contained in the flexible layer 14 in the multilayer film 1 described above. When the flexible layer 14 contains the resin, the flexibility of the multilayer film for base material can be further improved.

[0164] The resin contained in the flexible layer in the multi-layer film for base material is preferably a resin other than ethylene-vinyl alcohol copolymer (EVOH, also known as saponified ethylene-vinyl acetate copolymer). By using such a resin in the flexible layer, the oxygen permeability of the base material under conditions of a temperature of 23°C and a relative humidity of 60% can be more easily increased.

[0165] The flexible layer in the multilayer film for base materials may contain only the resin in the flexible layer (i.e., it may consist of the resin in the flexible layer), or it may contain the resin in the flexible layer and other components (sometimes referred to as "other components" in this specification) (i.e., it may consist of the resin in the flexible layer and the other components).

[0166] The other components contained in the flexible layer in the multi-layer film for base material are not particularly limited and can be selected arbitrarily depending on the purpose. For example, the other components may be either resin components or non-resin components. The other components, which are resin components, are resins that do not fall under the category of resins in the flexible layer. 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.

[0167] 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 11 in the multilayer film 1 described above.

[0168] The other components contained in the flexible layer in the multi-layer film for base materials may be only one type, or may be two or more types. When there are two or more types, the combination and ratio thereof can be arbitrarily selected depending on the purpose.

[0169] In the flexible layer in the multilayer film for base material, the content of the resin in the flexible layer relative to the total mass of the flexible layer is preferably 50 to 100 mass%, more preferably 60 to 100 mass%, and may be, for example, any of 70 to 100 mass% and 85 to 100 mass%. The ratio is usually the same as the ratio of the resin content (parts by mass) in the flexible layer to the total content (parts by mass) of components that do not vaporize at room temperature in the composition for forming a flexible layer for a base material described below.

[0170] The content of the ethylene-vinyl alcohol copolymer in the flexible layer in the multilayer film for base material is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 1% by mass or less, and may be, for example, 0% by mass (the flexible layer in the multilayer film for base material does not contain the ethylene-vinyl alcohol copolymer). By having the content be equal to or less than the upper limit, the oxygen permeability of the base material becomes greater under conditions of a temperature of 23°C and a relative humidity of 60%. The above ratio is usually the same as the ratio of the content (parts by mass) of ethylene-vinyl alcohol copolymer to the total content (parts by mass) of components that do not vaporize at room temperature in the composition for forming a flexible layer for a base material described below.

[0171] The flexible layer in the multi-layer film for base material may be one layer (single layer) or may be two or more layers. When the flexible layer is made 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.

[0172] The thickness of the flexible layer in the multilayer film for base material is preferably 2 to 20 μm. When the thickness of the flexible layer is equal to or greater than the lower limit, the flexibility of the flexible layer is increased. When the thickness of the flexible layer is equal to or less than the upper limit, the flexible layer is prevented from becoming excessively thick. Here, "thickness of the flexible layer" means the thickness of the entire flexible layer; for example, the thickness of a flexible layer consisting of multiple layers means the total thickness of all layers that make up the flexible layer.

[0173] The ratio of the thickness of the flexible 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 flexibility of the multi-layer film for base material is increased. When the ratio is equal to or less than the upper limit, the thickness of the flexible layer is prevented from becoming excessive.

[0174] <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.

[0175] The pinhole resistant layer in the multi-layer film for base materials preferably contains a polyolefin resin. Examples of the polyolefin resin include polyethylene 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); polypropylene, and the like.

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

[0177] 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 a polyolefin-based resin. 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 11 in the multilayer film 1 described above.

[0178] The other components contained in the pinhole-resistant layer in the multi-layer film for base materials may be only one type, or may be two or more types. When there are two or more types, the combination and ratio thereof can be arbitrarily selected depending on the purpose.

[0179] The content of the polyolefin resin in the pinhole-resistant layer in the multilayer film for base material is preferably 50 to 100 mass%, more preferably 60 to 100 mass%, and may be, for example, any one of 70 to 100 mass% and 85 to 100 mass%, relative to the total mass of the pinhole-resistant layer. The above ratio is usually the same as the ratio of the polyolefin resin 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.

[0180] The pinhole-resistant layer in the multi-layer film for base materials may be one layer (single layer) or two or more layers. When the pinhole-resistant layer is made up 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.

[0181] The thickness of the pinhole-resistant layer in the multi-layer film for base material 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, "the 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.

[0182] The ratio of the thickness of the pinhole-resistant layer to the thickness of the multi-layer 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 pinhole resistance of the multi-layer film for base material is improved. When the ratio is equal to or less than the upper limit, the thickness of the pinhole-resistant layer is prevented from becoming excessive.

[0183] <Adhesive layer> The adhesive layer is a layer for adhering the base multi-layer film to the foamed resin layer, and contains an adhesive.

[0184] The adhesive is preferably an adhesive resin, and 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 besides these. A preferred example of the ethylene-vinyl acetate copolymer resin is a partially saponified ethylene-vinyl acetate copolymer.

[0185] 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).

[0186] The adhesive layer in the multi-layer film for base materials may contain only one type of adhesive, or may contain two or more types. When there are two or more types, the combination and ratio thereof can be selected arbitrarily depending on the purpose.

[0187] The other components contained in the adhesive 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.

[0188] The other components contained in the adhesive layer in the multi-layer film for base materials may be only one type, or may be two or more types. When there are two or more types, the combination and ratio thereof can be arbitrarily selected depending on the purpose.

[0189] 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 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 an adhesive layer for a base material described below.

[0190] The adhesive layer in the multi-layer film for base material may be one layer (single layer) or may be two or more layers. When the adhesive layer is made 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.

[0191] The thickness of the adhesive layer in the base material multilayer film 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.

[0192] The ratio of the thickness of the adhesive layer to the thickness of the multi-layer 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 adhesive strength of 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.

[0193] <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. The adhesive resin may be, for example, a polyolefin resin. 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.

[0194] Examples of the ethylene-based copolymer include the ethylene-based copolymers described above as contained in the easy-peel layer, modified products thereof (modified copolymers), and the like. Examples of the propylene-based copolymer include a copolymer of propylene and a vinyl group-containing monomer, a modified product thereof (modified copolymer), etc. More specifically, examples of such a propylene-based copolymer include a maleic anhydride-grafted linear low-density polypropylene, a propylene-based thermoplastic elastomer, etc. Examples of the butene copolymer include copolymers of 1-butene and vinyl group-containing monomers, copolymers of 2-butene and vinyl group-containing monomers, and modified products of these copolymers (modified copolymers).

[0195] The first intermediate adhesive layer and the second intermediate adhesive layer may contain only an adhesive (i.e., may consist of an adhesive), or may contain an adhesive and other components (sometimes referred to as "other components" in this specification) (i.e., may consist of an adhesive and the other components).

[0196] The first intermediate adhesive layer and the second intermediate adhesive layer may contain only one type of adhesive, or two or more types, and if there are two or more types, the combination and ratio of these can be selected arbitrarily depending on the purpose.

[0197] 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.

[0198] The other components contained in the first intermediate adhesive layer and the second intermediate adhesive layer may be only one type, 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.

[0199] 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 a base material 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.

[0200] The first and second intermediate adhesive layers in the multilayer film for base materials may each be composed of one layer (single layer) or two or more layers. When the first or second intermediate adhesive layer is composed 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.

[0201] The thicknesses of the first and second intermediate adhesive layers in the multilayer film for base material are preferably each independently 2 to 15 μm. When the thicknesses of the first and second intermediate adhesive layers 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 and second intermediate adhesive layers are equal to or less than the upper limit, the first and second intermediate adhesive layers 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, and the same applies to the second intermediate adhesive layer.

[0202] The ratio of the thickness of the first intermediate adhesive layer and the second intermediate adhesive layer to the thickness of the multi-layer 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.

[0203] <Other layers> The multilayer film for base materials may have other layers that do not fall under any of the easy peel layer, the first intermediate adhesive layer, the soft layer, the second intermediate adhesive layer, the pinhole resistant layer, and the adhesive layer, within a range that does not impair the effects of the present invention.

[0204] The types and positions of the other layers in the multi-layer film for base material are not particularly limited and can be selected arbitrarily depending on the purpose.

[0205] The other layer that the multi-layer film for base materials has may be of only one type, or of two or more types. When there are two or more types, the combination and ratio thereof can be arbitrarily selected according to the purpose.

[0206] The other layers in the multi-layer film for base material may be one layer (single layer) or two or more layers per type. When the other layers are 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.

[0207] 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.

[0208] When the multilayer film for base materials has the other layers, it may further have an intermediate adhesive layer for adhering the other layers 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.

[0209] The thickness of the non-foamed resin layer of the multi-layer film for base material and the like is not particularly limited, but is preferably 40 to 120 μm.

[0210] <<Solid material 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 having the above-mentioned foamed resin layer and non-foamed resin layer, one side of the foamed resin layer and one side of the non-foamed resin layer (when the non-foamed resin layer is the multi-layer film for base material, the adhesive layer therein) can be bonded together by heat lamination to produce the base material. The heat lamination at this time may be performed, for example, by a melt pressure lamination method as described later in the examples, or may be performed by an extrusion lamination method. Of the non-foamed resin layers, the multi-layer film for base material can be produced by the same method as the multi-layer film (cover material) described above, except that the types of resins or resin compositions that are the materials for forming each layer are different.

[0211] Regardless of the manufacturing method, the resin composition that is the material for forming any of the layers in the multi-layer film for base material may be manufactured by adjusting the type and content of the components contained so that the layer to be formed contains the desired components (constituent materials) in the desired content. For example, the content ratio of the components that do not vaporize at room temperature in the resin composition is usually the same as the content ratio of the components in the layer formed from this resin composition.

[0212] The resin composition for forming the easy peel layer in the multilayer film for base material (sometimes referred to in this specification as "composition for forming easy peel layer for base material") may, for example, contain the polyolefin and, if necessary, the other components described above.

[0213] Resin compositions for forming a flexible layer in a multilayer film for base materials (sometimes referred to in this specification as "compositions for forming a flexible layer for base materials") include, for example, those containing a resin for the flexible layer and, if necessary, the other components described above.

[0214] 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 a pinhole-resistant layer for base materials") include, for example, those containing the polyolefin and, if necessary, the other components described above.

[0215] The resin composition for forming the adhesive layer in the multilayer film for base material (sometimes referred to in this specification as "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 "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 "composition for forming a second intermediate adhesive layer for base material") all contain, for example, the adhesive and, if necessary, the other components described above.

[0216] <<Packaging>> FIG. 2 is a cross-sectional view illustrating an example of the packaging body of the present embodiment. In FIG. 2, the same components as those shown in the drawings already described are given the same reference numerals as in the drawings already described, and detailed description thereof will be omitted. In FIG. 2, the distinction between the layers in the multilayer film 1 is omitted.

[0217] The packaging body 10 shown here is configured to include the multilayer film (covering material) 1 shown in FIG.

[0218] The package 10 is preferably a skin pack package. In this specification, "skin pack" refers to a package in which the contents are placed on cardboard, corrugated board, bottom film, tray, etc., and then a heated film is placed over the contents, 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.

[0219] In the packaging body 10, the multilayer film (lid material) 1 is configured by laminating a sealant layer 11, a conforming layer 13, and a soft layer 14 in the thickness direction. In the packaging body 10, the ratio of the thickness of the flexible layer 14 to the thickness of the multilayer film (lid material) 1 is 2 to 30%. In the packaging body 10, the tensile strength of the multilayer film (lid material) 1 at a temperature of 140° C. is 0.2 N / mm 2 More than 3.6N / mm 2 The following is the result. In the packaging body 10, the oxygen permeability of the multilayer film (covering material) 1 under conditions of a temperature of 23° C. and a relative humidity of 60% is 100 cc / (m 2 ·day·atm). In the packaging body 10, the dynamic elastic modulus E' of the multilayer film (lid material) 1 at a temperature of 140°C is 1 x 10 4 Pa or more 1×10 7 It is preferable that the pressure is 0.1 Pa or less. In the packaging body 10, it is preferable that the temperature at which the multilayer film (covering material) 1 shows a displacement of 2000 μm during thermomechanical analysis is 120° C. or higher. In the packaging body 10, the gel fraction of the multilayer film (covering material) 1 is preferably 30% or more. In the packaging body 10, it is preferable that the displacement of the multilayer film (covering material) 1 at a temperature of 100° C. is 500 μm or less during the thermomechanical analysis. In the packaging body 10, the multilayer film (covering material) 1 is preferably irradiated with electron beams under conditions of an absorbed dose of 13 to 300 kGy. In the packaging body 10, the flexible layer 14 preferably contains a polyethylene-based resin. In the packaging body 10, the ratio of the thickness of the conforming layer 13 to the thickness of the multilayer film (lid material) 1 is preferably 10% or more. In the packaging body 10, the ratio of the thickness of the sealant layer 11 to the thickness of the multilayer film (lid material) 1 is preferably 5% or more. In the packaging body 10, the tensile strength of the multilayer film (lid material) 1 at a temperature of 140° C. is 0.2 N / mm 2 More than 3N / mm 2 It is preferable that:

[0220] In the packaging body 10, the oxygen permeability of the base material 8 under conditions of a temperature of 23° C. and a relative humidity of 60% is 100 cc / (m 2 It is preferable that the temperature is greater than 100°C (day atm).

[0221] The packaging body 10 uses the multilayer film 1 as a lid material, and thus is able to maintain the quality of the contents, has excellent conformability to the contents, and is able to conform softly to the contents.

[0222] One surface 8a of the base material 8 (sometimes referred to as the "first surface" in this specification) is a sealing surface, and a part of the first surface 8a is sealed and adheres to a part of the first surface 11a of the sealant layer 11 in the multilayer film 1. In FIG. 2, the area where the first surface 8a of the base material 8 and the first surface 11a of the sealant layer 11 in the multilayer film 1 are in direct contact is the sealed portion. As a result, a storage portion 10a is formed between the first surface 8a of the base material 8 and the first surface 11a of the sealant layer 11. The content 9 is sealed in the storage portion 10a.

[0223] When the base material 8 is the multi-layer film for a base material, the first surface 8a of the base material 8 is the surface of the easy-peel layer opposite to the soft layer side.

[0224] 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.

[0225] 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 without departing from the spirit of the present invention. FIG. 2 shows a packaging body 10 constructed using the multilayer film 1 shown in FIG. 1 as a lid material, but the packaging body of this embodiment may be constructed using other multilayer films (lid materials).

[0226] <<Manufacturing method of packaging body>> The method of the present embodiment is a method for manufacturing a package in which contents are packaged with a lid material and a base material. The method of the present embodiment may be a method for manufacturing a package in which contents are vacuum-packaged with a lid material and a base material.

[0227] The method for producing a package of this embodiment includes the steps of: arranging the contents on the base material, arranging the lid material in an area on the base material that covers the contents and its periphery, and heating the lid material to 90 to 250°C while contacting the contents and molding it to fit the contents, and bonding (sealing) the portion of the lid material that is in contact with the base material to the base material, thereby packaging the contents with the lid material and the base material. A test package described later can also be produced by the method for producing a package of this embodiment.

[0228] In the process of placing the contents on the base material, for example, when a resin laminate having the multi-layer film for base material described above is used as the base material, the contents are placed on the easy-peel layer in the multi-layer film for base material.

[0229] In the step of placing the lid material, the multilayer film described above is placed with the sealant layer facing the base material and food.

[0230] In the process of packaging the contents with the lid material and the base material by heating the lid material to 90 to 250°C, bringing the lid material into contact with the contents and molding it to fit the contents, and adhering the portion of the lid material that is in contact with the base material to the base material, the area between the base material and the lid material where the contents are placed may be vacuumed.

[0231] The heating temperature for heating the lid material is preferably 100 to 170° C., more preferably 105 to 170° C., and even more preferably 110 to 170° C. When the heating temperature is equal to or higher than the lower limit, the seal strength is increased while maintaining easy peelability. When the heating temperature is equal to or lower than the upper limit, the package is easier to open.

[0232] The heating time for heating the lid material to 90 to 250°C can be adjusted appropriately depending on the heating temperature, but is usually preferably 10 to 30 seconds. By setting the heating time to the lower limit or more, the seal strength is increased while maintaining easy peelability. By setting the heating time to the upper limit or less, the package is easier to open.

[0233] When the region in which the contents are placed is evacuated, the pressure in this region is preferably 0 to 10,000 Pa (100 mbar), more preferably 0 to 9,000 Pa (90 mbar), and even more preferably 0 to 8,000 Pa (80 mbar). By keeping the pressure below the upper limit, the cover material has higher conformability (adhesion) to the contents, and a package having better storage suitability can be obtained.

[0234] The pressure when the portion of the lid material in contact with the base material is adhered (sealed) to the base material is preferably 0 to 1000 Pa (100 mbar), more preferably 0 to 9000 Pa (90 mbar), and even more preferably 0 to 8000 Pa (80 mbar). By keeping the pressure at or below the upper limit, a package having a good peeling feel can be obtained. EXAMPLES

[0235] The present invention will be described in more detail below with reference to specific examples, although the present invention is not limited to the following examples.

[0236] [Example 1] <<Manufacturing of multi-layer films (covering materials)>> A multilayer film having the structure shown in FIG. 1 was produced according to the procedure described below. That is, an ethylene-vinyl acetate copolymer (EVA, "V5714C" manufactured by Dow Mitsui Polychemicals) was prepared as a resin constituting the sealant layer. The resin that constitutes the outer layer is low-density polyethylene (LDPE, density 0.922 g / cm 3and "F222NH" manufactured by Ube Maruzen Polyethylene Co., Ltd.) were prepared. As a resin for forming the follow-up layers (first follow-up layer and second follow-up layer), a sodium-based ionomer (ION, "1601" manufactured by Dow Mitsui Polychemicals) was prepared. Metallocene linear low-density polyethylene (mLLDPE, "4040FC" manufactured by Ube Maruzen Polyethylene Co., Ltd.) was prepared as the resin constituting the flexible layer. As an adhesive (adhesive resin) constituting the adhesive layers (first adhesive layer and second adhesive layer), maleic anhydride modified polyethylene (modified PE, "NF536" manufactured by Mitsui Chemicals, Inc.) was prepared.

[0237] The die temperature was set to 250°C, and the EVA, the ION, the modified PE, the mLLDPE, the modified PE, the ION, and the LDPE were co-extruded in this order (co-extrusion T-die method) to produce a multilayer film (thickness 120 μm) composed of a sealant layer (thickness 24 μm), a follower layer (first follower layer, thickness 29 μm), an adhesive layer (first adhesive layer, thickness 8 μm), a soft layer (thickness 10 μm), an adhesive layer (second adhesive layer, thickness 8 μm), a follower layer (second follower layer, thickness 17 μm), and an outer layer (thickness 24 μm) laminated in this order in the thickness direction.

[0238] Next, the multilayer film obtained above was irradiated with an electron beam from the outside of the outer layer side under conditions of an absorbed dose of 175 kGy and an accelerating voltage of 160 kV. In this manner, the desired electron beam irradiated multilayer film (hereinafter sometimes referred to as "covering material (I)") was obtained.

[0239] <<Evaluation of multi-layer film (covering material)>> <Measurement of tensile strength at 140℃> The tensile strength of the electron beam irradiated multilayer film (covering material (I)) obtained above was measured using a tensile strength measuring device (Shimadzu Corporation's "AGS-X") in accordance with JIS K 7127: 1999 at a tensile speed of 500 mm / min. The results are shown in Table 1.

[0240] <Measurement of dynamic elastic modulus at 140℃> The dynamic modulus of elasticity (E') of the electron beam irradiated multilayer film (covering material (I)) obtained above was measured in accordance with JIS K7244-4 using a dynamic viscoelasticity measuring device (Hitachi High-Tech Science Corporation "DMA 7100") in a tensile mode in the temperature range of 25°C to 160°C, with a displacement of 10μm, a vibration frequency of 1Hz, and a heating rate of 3°C / min, using a 4mm wide sample. The results are shown in Table 1.

[0241] <Identifying the temperature at which a displacement of 2000 μm occurs, and the displacement at a temperature of 100°C> The electron beam irradiated multilayer film (covering material (I)) obtained above was subjected to thermomechanical analysis in accordance with JIS K 7196 using a thermal analyzer ("EXSTAR6000" manufactured by SII Corporation). From the obtained thermomechanical analysis curve, the temperature (°C) showing a displacement of 2000 μm and the displacement (μm) at a temperature of 100°C were obtained. The results are shown in Table 1.

[0242] <Measurement of gel fraction> The gel fraction of the electron beam irradiated multilayer film (covering material (I)) obtained above was measured in accordance with JIS K 6769. That is, a test piece measuring 3 cm x 3 cm (approximately 0.09 g) was cut out from the multilayer film, wrapped in a 400 mesh stainless steel wire net (100 g), and immersed in xylene (18 mL) at 110°C for 24 hours. Next, the test piece together with the wire mesh was taken out of the xylene and vacuum dried at 110°C for 24 hours under a pressure of 1.7 kPa to obtain a dried product of the test piece after immersion. The mass of the obtained dried product was measured to determine the gel fraction (%) of the multilayer film irradiated with electron beams. The results are shown in Table 1.

[0243] <Oxygen permeability measurement> The electron beam irradiated multilayer film (covering material (I)) obtained above was measured for oxygen permeability (cc / (m)) in accordance with JIS K 7126-2:2006 under conditions of a temperature of 23°C and a relative humidity of 60%.2 The results are shown in Table 1.

[0244] <Evaluation of soft layer breakage> The flexible layer of the electron beam irradiated multilayer film (covering material (I)) obtained above was visually observed and evaluated for the presence or absence of layer breakage in the flexible layer according to the following criteria. The results are shown in Table 1. [Evaluation criteria] A: There is no separation of the flexible layer. B: The flexible layer is slightly torn. C: The flexible layer is torn.

[0245] <<Manufacture of base material>> <Manufacture of multi-layer film for base materials> A multi-layer film for base material was produced according to the following procedure. That is, low-density polyethylene (LDPE, "L211" manufactured by Sumitomo Chemical Co., Ltd.) and polypropylene (PP, "FS2011DG2" manufactured by Sumitomo Chemical Co., Ltd.) were prepared as resins constituting the easy-peel layer. The resin constituting the pinhole-resistant layer was metallocene-catalyzed linear low-density polyethylene (mLLDPE) (Ube Maruzen Polyethylene Co., Ltd. "Yumerit (registered trademark) 1520F", density 0.913 g / cm 3 ) was prepared. The resin constituting the flexible layer was a metallocene linear low-density polyethylene (mLLDPE, Ube Maruzen Polyethylene Co., Ltd. "4040FC", density: 0.938 kg / m 3 , MFR: 3.5g / 10min) was prepared. As the resin constituting the first intermediate adhesive layer, acid-modified polypropylene (acid-modified PP, adhesive resin, "Admer QF551" manufactured by Mitsui Chemicals) was prepared. As the resin constituting the second intermediate adhesive layer, acid-modified polyethylene (acid-modified PE, adhesive resin, "Admer NF536" manufactured by Mitsui Chemicals) was prepared. As the resin constituting the adhesive layer, an ethylene-vinyl acetate copolymer resin (EVA resin, adhesive resin, "MELCENE (registered trademark) MX02D" manufactured by Tosoh Corporation was prepared.

[0246] The LDPE (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.

[0247] The die temperature was set to 250°C, and the composition for forming the easy peel layer for the base material, the acid-modified PP, the mLLDPE, the acid-modified PE, the mLLDPE, and the EVA-based resin were co-extruded in this order (co-extrusion T-die method) to produce a multilayer film for the base material (thickness 70 μm) composed of an easy peel layer (thickness 25.9 μm), a first intermediate adhesive layer (thickness 5.6 μm), a flexible layer (thickness 8.4 μm), a second intermediate adhesive layer (thickness 5.6 μm), a pinhole-resistant layer (thickness 10.5 μm), and an adhesive layer (thickness 14 μm) laminated in the thickness direction in this order.

[0248] <Manufacture of sole materials> A foamed resin sheet (manufactured by Chuo Kagaku 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 attached 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 is configured to have a heating roll and an opposing roll disposed opposite the heating roll, and the foamed resin sheet and the multi-layer film for base material were melt-pressed at 180°C between the heating roll and the opposing roll to bond them together.

[0249] <<Evaluation of base material>> <Oxygen transmission rate measurement> The oxygen permeability (cc / (m) of the base material (base material (α)) obtained above was measured in accordance with JIS K 7126-2:2006 under the conditions of a temperature of 23°C and a relative humidity of 60%. 2 The results are shown in Table 5.

[0250] <<Manufacturing of packaging (test packaging)>> A chicken thigh meat with a mass of 400 g was cut out and used as the test meat. Then, in a continuous skin pack packaging machine (Multivac's "T300"), the sealant layer in the lid material (I) and the easy peel layer in the base material (α) were placed opposite each other, and the test meat was placed between the lid material (I) and the base material (α). While evacuating the area where the test meat was placed, the periphery of the lid material (I) and the base material (α) were heat-sealed under conditions of a hot plate temperature (sealing temperature) of 140°C and a sealing time of 10 seconds, thereby producing a test package (skin pack package). When evacuating, the pressure in the area where the test meat was placed was set to 1000 Pa (10 mbar). The base material (α) used had a size of 20 cm x 20 cm. A plurality of test packages were prepared by the same procedure, and these test packages were frozen and stored at -30°C in an air atmosphere.

[0251] <<Evaluation of packaging (test packaging)>> <Contents Shape> Three days after the start of storage, the meat was thawed from a frozen state of -30°C to 4°C over a period of 16 hours. Immediately after thawing, the unopened test packages were visually observed from the lid side, and the shape of the test meat was evaluated according to the following criteria. The results are shown in Table 6. [Evaluation Criteria] A: The shape of the test meat is maintained. B: The shape of the test meat is slightly crushed. C: The shape of the test meat is crushed.

[0252] <Discoloration of contents> Three days after the start of storage, the meat was thawed from a frozen state of -30°C to 4°C over a period of 16 hours. Immediately after thawing, the unopened test packages were visually observed from the lid side and the presence or absence of discoloration of the test meat (surface oxidative discoloration) was evaluated according to the following criteria. The results are shown in Table 6. [Evaluation Criteria] A: No discoloration of the test meat has occurred. B: The test meat is slightly discolored. C: Discoloration of the test meat has occurred.

[0253] <Drip> Three days after the start of storage, the meat was thawed from a frozen state of -30°C to 4°C over a period of 16 hours. Immediately after thawing, the test meat was removed from the unopened test package and left for 5 minutes before being visually observed and the amount of dripping was evaluated according to the following criteria. The results are shown in Table 6. [Evaluation Criteria] A: No dripping occurs. B: There is some dripping. C: Dripping is occurring.

[0254] [Example 2] An electron beam irradiated multilayer film (hereinafter sometimes referred to as "covering material (II)") was produced and evaluated in the same manner as in Example 1, except that the absorbed dose when irradiating the multilayer film with electron beams was 120 kGy instead of 175 kGy. A package (test package) was produced and evaluated in the same manner as in Example 1, except that this electron beam irradiated multilayer film (covering material (II)) was used. The results are shown in Tables 1, 5 and 6.

[0255] [Example 3] An electron beam irradiated multilayer film (hereinafter sometimes referred to as "covering material (III)") was produced and evaluated in the same manner as in Example 1, except that the absorbed dose when irradiating the multilayer film with electron beams was 90 kGy instead of 175 kGy. A package (test package) was produced and evaluated in the same manner as in Example 1, except that this electron beam irradiated multilayer film (covering material (III)) was used. The results are shown in Tables 1, 5 and 6.

[0256] [Example 4] An electron beam irradiated multilayer film (hereinafter sometimes referred to as "covering material (IV)") was produced and evaluated in the same manner as in Example 1, except that the absorbed dose when irradiating the multilayer film with electron beams was 15 kGy instead of 175 kGy. A package (test package) was produced and evaluated in the same manner as in Example 1, except that this electron beam irradiated multilayer film (covering material (IV)) was used. The results are shown in Tables 1, 5 and 6.

[0257] [Comparative Example 1] A lid material (a multilayer film not irradiated with electron beams, hereinafter sometimes referred to as "lid material (V)") was manufactured and evaluated in the same manner as in Example 1, except that the multilayer film was not irradiated with electron beams. A package (test package) was produced and evaluated in the same manner as in Example 1, except that this multilayer film (covering material (V)) that had not been irradiated with electron beams was used. The results are shown in Tables 1, 5 and 8.

[0258] [Example 5] The die temperature was set to 250°C, and the EVA, the ION, the modified PE, the mLLDPE, the modified PE, the ION, and the LDPE were co-extruded in this order (co-extrusion T-die method) to produce a multilayer film (thickness 120 μm) in which a sealant layer (thickness 20 μm), a follower layer (first follower layer, thickness 29 μm), an adhesive layer (first adhesive layer, thickness 8 μm), a soft layer (thickness 18 μm), an adhesive layer (second adhesive layer, thickness 8 μm), a follower layer (second follower layer, thickness 17 μm), and an outer layer (thickness 20 μm) were laminated in this order in the thickness direction. Except for this, a lid material (electron beam irradiated multilayer film, hereinafter sometimes referred to as "lid material (VI)") was produced and evaluated in the same manner as in Example 1. A package (test package) was produced and evaluated in the same manner as in Example 1, except that this electron beam irradiated multilayer film (covering material (VI)) was used. The results are shown in Tables 1, 5 and 6.

[0259] [Example 6] The die temperature was set to 250°C, and the EVA, the ION, the modified PE, the mLLDPE, the modified PE, the ION, and the LDPE were co-extruded in this order (co-extrusion T-die method) to produce a multilayer film (thickness 120 μm) in which a sealant layer (thickness 16 μm), a follower layer (first follower layer, thickness 29 μm), an adhesive layer (first adhesive layer, thickness 8 μm), a soft layer (thickness 26 μm), an adhesive layer (second adhesive layer, thickness 8 μm), a follower layer (second follower layer, thickness 17 μm), and an outer layer (thickness 16 μm) were laminated in this order in the thickness direction. Except for this, a lid material (electron beam irradiated multilayer film, hereinafter sometimes referred to as "lid material (VII)") was produced and evaluated in the same manner as in Example 1. A package (test package) was produced and evaluated in the same manner as in Example 1, except that this electron beam irradiated multilayer film (covering material (VII)) was used. The results are shown in Tables 2, 5 and 6.

[0260] [Example 7] The die temperature was set to 250°C, and the EVA, the ION, the modified PE, the mLLDPE, the modified PE, the ION, and the LDPE were co-extruded in this order (co-extrusion T-die method) to produce a multilayer film (thickness 120 μm) in which a sealant layer (thickness 12 μm), a follower layer (first follower layer, thickness 29 μm), an adhesive layer (first adhesive layer, thickness 8 μm), a soft layer (thickness 34 μm), an adhesive layer (second adhesive layer, thickness 8 μm), a follower layer (second follower layer, thickness 17 μm), and an outer layer (thickness 12 μm) were laminated in this order in the thickness direction. Except for this, a lid material (electron beam irradiated multilayer film, hereinafter sometimes referred to as "lid material (VIII)") was produced and evaluated in the same manner as in Example 1. A package (test package) was produced and evaluated in the same manner as in Example 1, except that this electron beam irradiated multilayer film (covering material (VIII)) was used. The results are shown in Tables 2, 5 and 6.

[0261] [Example 8] The die temperature was set to 250°C, and the EVA, the ION, the modified PE, the mLLDPE, the modified PE, the ION, and the LDPE were co-extruded in this order (co-extrusion T-die method) to produce a multilayer film (thickness 120 μm) in which a sealant layer (thickness 27 μm), a follower layer (first follower layer, thickness 29 μm), an adhesive layer (first adhesive layer, thickness 8 μm), a soft layer (thickness 4 μm), an adhesive layer (second adhesive layer, thickness 8 μm), a follower layer (second follower layer, thickness 17 μm), and an outer layer (thickness 27 μm) were laminated in this order in the thickness direction. Except for this, a lid material (electron beam irradiated multilayer film, hereinafter sometimes referred to as "lid material (IX)") was produced and evaluated in the same manner as in Example 1. A package (test package) was produced and evaluated in the same manner as in Example 1, except that this electron beam irradiated multilayer film (covering material (IX)) was used. The results are shown in Tables 2, 5 and 7.

[0262] [Comparative Example 2] The die temperature was set to 250°C, and the EVA, the ION, the modified PE, the mLLDPE, the modified PE, the ION, and the LDPE were co-extruded in this order (co-extrusion T-die method) to produce a multilayer film (thickness 120 μm) in which a sealant layer (thickness 28 μm), a follower layer (first follower layer, thickness 29 μm), an adhesive layer (first adhesive layer, thickness 8 μm), a soft layer (thickness 1 μm), an adhesive layer (second adhesive layer, thickness 8 μm), a follower layer (second follower layer, thickness 17 μm), and an outer layer (thickness 29 μm) were laminated in this order in the thickness direction. Except for this, a lid material (electron beam irradiated multilayer film, hereinafter sometimes referred to as "lid material (X)") was produced and evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0263] [Example 9] The die temperature was set to 250°C, and the EVA, the ION, the modified PE, the mLLDPE, the modified PE, the ION, and the LDPE were co-extruded in this order (co-extrusion T-die method) to produce a multilayer film (thickness 120 μm) in which a sealant layer (thickness 32 μm), a follower layer (first follower layer, thickness 21 μm), an adhesive layer (first adhesive layer, thickness 8 μm), a soft layer (thickness 10 μm), an adhesive layer (second adhesive layer, thickness 8 μm), a follower layer (second follower layer, thickness 9 μm), and an outer layer (thickness 32 μm) were laminated in this order in the thickness direction. Except for this, a lid material (electron beam irradiated multilayer film, hereinafter sometimes referred to as "lid material (XI)") was produced and evaluated in the same manner as in Example 1. A package (test package) was produced and evaluated in the same manner as in Example 1, except that this electron beam irradiated multilayer film (covering material (XI)) was used. The results are shown in Tables 2, 5 and 7.

[0264] [Example 10] The die temperature was set to 250°C, and the EVA, the ION, the modified PE, the mLLDPE, the modified PE, the ION, and the LDPE were co-extruded in this order (co-extrusion T-die method) to produce a multilayer film (thickness 120 μm) in which a sealant layer (thickness 40 μm), a follower layer (first follower layer, thickness 7 μm), an adhesive layer (first adhesive layer, thickness 8 μm), a soft layer (thickness 10 μm), an adhesive layer (second adhesive layer, thickness 8 μm), a follower layer (second follower layer, thickness 7 μm), and an outer layer (thickness 40 μm) were laminated in this order in the thickness direction. Except for this, a lid material (electron beam irradiated multilayer film, hereinafter sometimes referred to as "lid material (XII)") was produced and evaluated in the same manner as in Example 1. A package (test package) was produced and evaluated in the same manner as in Example 1, except that this electron beam irradiated multilayer film (covering material (XII)) was used. The results are shown in Tables 3, 5 and 7.

[0265] [Example 11] The die temperature was set to 250°C, and the EVA, the ION, the modified PE, the mLLDPE, the modified PE, the ION, and the LDPE were co-extruded in this order (co-extrusion T-die method) to produce a multilayer film (thickness 120 μm) in which a sealant layer (thickness 41 μm), a follower layer (first follower layer, thickness 6 μm), an adhesive layer (first adhesive layer, thickness 8 μm), a soft layer (thickness 10 μm), an adhesive layer (second adhesive layer, thickness 8 μm), a follower layer (second follower layer, thickness 5 μm), and an outer layer (thickness 42 μm) were laminated in this order in the thickness direction. Except for this, a lid material (electron beam irradiated multilayer film, hereinafter sometimes referred to as "lid material (XIII)") was produced and evaluated in the same manner as in Example 1. A package (test package) was produced and evaluated in the same manner as in Example 1, except that this electron beam irradiated multilayer film (covering material (XIII)) was used. The results are shown in Tables 3, 5 and 7.

[0266] [Comparative Example 3] Instead of the mLLDPE (Ube Maruzen Polyethylene Co., Ltd. "4040FC"), 6-nylon (Ny, Ube Industries, Ltd. "1030B2") was used as the resin constituting the flexible layer. The die temperature was set to 250°C, and the EVA, the ION, the modified PE, the Ny, the modified PE, the ION, and the LDPE were co-extruded in this order (co-extrusion T-die method). By this, a sealant layer (thickness 24 μm), a follower layer (first follower layer, thickness 2 A lid material (electron beam irradiated multilayer film, hereinafter sometimes referred to as "lid material (XIV)") was manufactured and evaluated in the same manner as in Example 1, except that a multilayer film (thickness 120 μm) was manufactured by stacking in the thickness direction, in the following order, a first adhesive layer (thickness 9 μm), an adhesive layer (first adhesive layer, thickness 8 μm), a flexible layer (thickness 9 μm), an adhesive layer (second adhesive layer, thickness 8 μm), a follower layer (second follower layer, thickness 17 μm) and an outer layer (thickness 25 μm). A package (test package) was produced and evaluated in the same manner as in Example 1, except that this electron beam irradiated multilayer film (covering material (XIV)) was used. The results are shown in Tables 3, 5 and 8.

[0267] [Example 12] Instead of the mLLDPE (Ube Maruzen Polyethylene Co., Ltd. "4040FC"), 6-nylon (Ny, Ube Industries, Ltd. "1030B2") was used as the resin constituting the flexible layer, the die temperature was set to 250°C, and the EVA, the ION, the modified PE, the Ny, the modified PE, the ION, and the LDPE were co-extruded in this order (co-extrusion T-die method), to produce a sealant layer (thickness 29 μm), a follower layer (first follower layer, thickness 10 μm), and a 100 μm thick follower layer (second follower layer, thickness 10 μm). A lid material (electron beam irradiated multilayer film, hereinafter sometimes referred to as "lid material (XV)") was manufactured and evaluated in the same manner as in Example 1, except that a multilayer film (thickness 120 μm) was manufactured by laminating in the thickness direction, in the following order, a first adhesive layer (thickness 29 μm), an adhesive layer (first adhesive layer, thickness 8 μm), a flexible layer (thickness 5 μm), an adhesive layer (second adhesive layer, thickness 8 μm), a follower layer (second follower layer, thickness 17 μm) and an outer layer (thickness 24 μm). A package (test package) was produced and evaluated in the same manner as in Example 1, except that this electron beam irradiated multilayer film (covering material (XV)) was used. The results are shown in Tables 3, 5 and 7.

[0268] [Comparative Example 4] As a resin constituting the flexible layer, 6-nylon (Ny, Ube Industries, Ltd., "1030B2") is used instead of the mLLDPE (Ube Maruzen Polyethylene Co., Ltd., "4040FC"), and as a resin constituting the second adhesive layer, ethylene-vinyl alcohol copolymer (EVOH, Kuraray Co., Ltd., "J171B") is used instead of the modified PE (Mitsui Chemicals, Inc., "NF536"). The die temperature is set to 250°C, and the EVA, ION, modified PE, Ny, EVOH, ION, and LDPE are co-extruded in this order. A multilayer film (thickness 120 μm) was produced by laminating a sealant layer (thickness 24 μm), a follower layer (first follower layer, thickness 40 μm), an adhesive layer (first adhesive layer, thickness 8 μm), a soft layer (thickness 24 μm), an adhesive layer (second adhesive layer, thickness 6 μm), a follower layer (second follower layer, thickness 10 μm) and an outer layer (thickness 8 μm) in this order in the thickness direction by co-extrusion (T-die method). A lid material (electron beam irradiated multilayer film, hereinafter sometimes referred to as "lid material (XVI)") was produced and evaluated in the same manner as in Example 1, except that this electron beam irradiated multilayer film (lid material (XVI)) was used. A package (test package) was produced and evaluated in the same manner as in Example 1. The results are shown in Tables 3, 5 and 8.

[0269] [Example 13] As the resin constituting the outer layer, linear low-density polyethylene (LLDPE, density 0.938 g / cm) was used instead of the LDPE ("F222NH" manufactured by Ube Maruzen Polyethylene Co., Ltd.). 3 A lid material (electron beam irradiated multilayer film, hereinafter sometimes referred to as "lid material (XVII)") was manufactured and evaluated in the same manner as in Example 1, except that a lid material (electron beam irradiated multilayer film, hereinafter sometimes referred to as "lid material (XVII)") was used. A package (test package) was produced and evaluated in the same manner as in Example 1, except that this electron beam irradiated multilayer film (covering material (XVII)) was used. The results are shown in Tables 4, 5 and 7.

[0270] [Example 14] As the resin constituting the outer layer, high density polyethylene (HDPE, density 0.949 g / cm) was used instead of the LDPE ("F222NH" manufactured by Ube Maruzen Polyethylene Co., Ltd.). 3 A lid material (electron beam irradiated multilayer film, hereinafter sometimes referred to as "lid material (XVIII)") was produced and evaluated in the same manner as in Example 1, except that a lid material (electron beam irradiated multilayer film, hereinafter sometimes referred to as "lid material (XVIII)") was used. A package (test package) was produced and evaluated in the same manner as in Example 1, except that this electron beam irradiated multilayer film (covering material (XVIII)) was used. The results are shown in Tables 4, 5 and 7.

[0271] [Example 15] A lid material (electron beam irradiated multilayer film, hereinafter sometimes referred to as "lid material (XIX)") was produced and evaluated in the same manner as in Example 1, except that an ethylene-vinyl acetate copolymer (EVA, Mitsui Dow Polychemicals' "V5714C") was used instead of the LDPE (Ube Maruzen Polyethylene's "F222NH") ​​as the resin constituting the outer layer. A package (test package) was produced and evaluated in the same manner as in Example 1, except that this electron beam irradiated multilayer film (lid material (XIX)) was used. The results are shown in Tables 4, 5 and 8.

[0272] [Example 16] A lid material (electron beam irradiated multilayer film, hereinafter sometimes referred to as "lid material (XX)") was manufactured and evaluated in the same manner as in Example 1, except that no outer layer was provided and the thickness of the second conformal layer was 41 μm. A package (test package) was produced and evaluated in the same manner as in Example 1, except that this electron beam irradiated multilayer film (covering material (XX)) was used. The results are shown in Tables 4, 5 and 8.

[0273] [Example 17] A lid material (electron beam irradiated multilayer film, hereinafter sometimes referred to as "lid material (XXI)") was manufactured and evaluated in the same manner as in Example 1, except that the first follow-up layer was not provided and the thickness of the sealant layer was 53 μm. A package (test package) was produced and evaluated in the same manner as in Example 1, except that this electron beam irradiated multilayer film (covering material (XXI)) was used. The results are shown in Tables 4, 5 and 8.

[0274] [Table 1]

[0275] [Table 2]

[0276] [Table 3]

[0277] [Table 4]

[0278] [Table 5]

[0279] [Table 6]

[0280] [Table 7]

[0281] [Table 8]

[0282] In the lid materials of the test packages of Examples 1 to 17, the ratio of the thickness of the soft layer to the thickness of the multilayer film was 2% or more, and therefore no breakage occurred in the soft layer in any of the packages.

[0283] The test packages of Examples 1 to 17 had a tensile strength of 3.6 N / mm 2 Because of this, the shape of the packaged test meat in the test package of Example 7 was slightly crushed, but the test packages of Examples 1 to 6 and 8 to 17 were all able to maintain the shape of the packaged test meat. The test packages of Examples 1 to 17 had an oxygen permeability of 100 cc / (m 2 Since the storage temperature was over 100°C (days atm), no discoloration of the packaged test meat occurred. The test packages of Examples 1 to 17 had a tensile strength of 0.2 N / mm 2 For the above reasons, although some dripping occurred in the test meat taken out of the test package of Example 11, no dripping occurred in any of the test packages of Examples 1 to 10 and 12 to 17.

[0284] Thus, the test packages of Examples 1 to 17 maintained the quality of the contents, had excellent conformability to the contents, and were able to conform softly to the contents.

[0285] In contrast, in the test package of Comparative Example 1, the multilayer film was not irradiated with electron beams, and the tensile strength at 140°C was 0.2 N / mm 2 Because the temperature was less than this, the ability of the lid material to conform to the test meat was reduced, and drips occurred in the test meat that was removed.

[0286] In the test package of Comparative Example 2, the ratio of the thickness of the flexible layer to the thickness of the multilayer film was less than 2%, so that the flexible layer was torn and there was a problem with the quality of the lid material. Therefore, the production and evaluation of a package (test package) using the lid material of Comparative Example 2 was not performed.

[0287] In the test package of Comparative Example 3, the Ny resin was used as the resin constituting the flexible layer, and the oxygen permeability of the multi-layer film was 100 cc / (m 2 The temperature dropped below 100°C (days atm), causing discoloration of the packaged test meat.

[0288] In the test package of Comparative Example 4, the Ny was used as the resin constituting the soft layer, and the oxygen permeability was 100 cc / (m 2 The test package of Comparative Example 4 used the EVOH as the resin constituting the second adhesive layer, and therefore the tensile strength at 140°C was 3.6 N / mm 2 As a result, the shape of the packaged test meat was distorted. [Industrial Applicability]

[0289] The present invention can provide a multilayer film that maintains the quality of the contents and has excellent conformability to the contents, and a package (for example, a skin pack package) using the same. [Explanation of symbols]

[0290] 1. Multi-layer film (covering material) 11. Sealant layer 12...outer layer 13. Follower layer 131...First Follower Layer 132...Second Follower Layer 14...Flexible layer 15...Adhesive layer 151...1st adhesive layer 152...Second adhesive layer 10... Packaging (test packaging) 8...Bottom material 9. Contents (Test Meat)

Claims

1. A multilayer film, The multilayer film is configured by laminating a sealant layer, a conforming layer, and a soft layer in a thickness direction thereof, The ratio of the thickness of the flexible layer to the thickness of the multilayer film is 15 to 30%; The tensile strength of the multilayer film at a temperature of 140°C measured in accordance with JIS K 7127:1999 is 2 N / mm ２ 3.6N / mm or more ２ is as follows: 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) and The multilayer film is irradiated with an electron beam at an absorbed dose of 175 to 300 kGy.

2. The dynamic elastic modulus E' of the multilayer film at a temperature of 140° C. is 1×10 ４ Pa or more 1×10 ７ The multilayer film of claim 1, wherein the elastic modulus is 0.05 Pa or less.

3. 3. The multilayer film according to claim 1, wherein the temperature at which the multilayer film shows a displacement of 2000 μm during thermomechanical analysis measured in accordance with JIS K 7196 is 120° C. or higher.

4. The multilayer film according to any one of claims 1 to 3, wherein the multilayer film has a gel fraction of 30% or more.

5. 4. The multilayer film of claim 3, wherein the multilayer film has a displacement of 500 μm or less at a temperature of 100° C. during the thermomechanical analysis.

6. The multilayer film according to any one of claims 1 to 5, wherein the flexible layer comprises a polyethylene-based resin.

7. The multilayer film according to any one of claims 1 to 6, wherein the ratio of the thickness of the compliant layer to the thickness of the multilayer film is 10% or more.

8. The multilayer film according to any one of claims 1 to 7, wherein the ratio of the thickness of the sealant layer to the thickness of the multilayer film is 5% or more.

9. The tensile strength of the multilayer film at a temperature of 140°C measured in accordance with JIS K 7127:1999 is 2 N / mm ２ 3N / mm or more ２ The multilayer film according to any one of claims 1 to 8, wherein:

10. A packaging material comprising the multilayer film according to any one of claims 1 to 9.

11. The package of claim 10, wherein the package is a skin pack package.

12. A method for manufacturing a package in which a content is packaged with a lid material and a base material, the method comprising the steps of: placing the content on the base material; placing the lid material in an area on the base material that covers the content and its periphery; and bringing the lid material into contact with the content while heating it to 90 to 250°C, molding it to fit the content, and adhering a portion of the lid material that is in contact with the base material to the base material, thereby packaging the content with the lid material and the base material, wherein the lid material is composed of the multilayer film according to any one of claims 1 to 9.

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