Multilayer film, packaging, and method for manufacturing packaging

Abstract

To provide a multilayer film which retains the quality of a stored object, has excellent followability to a stored object and can softly follow a stored object and to provide a package (for example, a skin pack package) using the same.SOLUTION: There is provided a multilayer film which is configured by laminating a sealant layer, a following layer and a flexible layer in the thickness direction, wherein the ratio of the thickness of the flexible layer to the thickness of the multilayer film is 2 to 30%, the tensile strength of the multilayer film at a temperature of 140°C is 0.2 N / mm2 or more and 3.6 N / mm2 or less, as measured in accordance with JIS K 7127:1999 and 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.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a multilayer film, a package, and a method for manufacturing a package.

Background Art

[0002] A package in which an object to be packaged (contents) is placed on a rigid tray and the contents are sealed with a film by evacuation is called a skin pack. In a skin pack, the film, that is, the film for the skin pack, is transparent, and the contents can be easily visually recognized through it. Further, the film for the skin pack is soft, and by evacuating the storage portion in the skin pack, it is possible to closely adhere to the contents without causing wrinkles (see, for example, Patent Document 1). And, since the skin pack includes a rigid tray (base material), it can be displayed upright without causing displacement of the position of the contents. In view of such characteristics, the skin pack is mainly used as a package for food.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

[0005] Furthermore, since foods such as chicken are generally irregular in shape, there was a problem in that the conformability of skin packaging to the food (the ability to adhere tightly without creating wrinkles) was reduced. In addition, the ability to adhere tightly to soft contents without crushing them is required to enhance product quality.

[0006] The present invention has been made in view of the above circumstances, and aims to provide a multilayer film that maintains the quality of the contents, has excellent conformability to the contents, and can softly conform to the contents, and a packaging body (for example, a skin pack packaging body) using the same. [Means for solving the problem]

[0007] To solve the above problems, the present invention adopts the following configuration. [1] A multilayer film comprising a sealant layer, a conforming layer, and a flexible layer, laminated in the thickness direction thereof, wherein the ratio of the thickness of the flexible layer to the thickness of the multilayer film is 2-30%, 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 / mm². 2 More than 3.6N / mm 2The following is 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%: 100 cc / (m 2 It is a multi-layer film that exceeds the limit of 'day' and 'atm'. [2] The dynamic modulus E' of the multilayer film at a temperature of 140°C is 1 × 10 4 Pa or more 1×10 7 A multilayer film as described in [1], having a Pa of less than or equal to Pa. [3] The multilayer film according to [1] or [2], wherein the temperature at which a displacement of 2000 μm is observed during thermomechanical analysis of the multilayer film is 120°C or higher. [4] The multilayer film according to any one of [1] to [3], wherein the gel fraction of the multilayer film is 30% or more. [5] The multilayer film according to [3], wherein the displacement at a temperature of 100°C during the thermomechanical analysis of the multilayer film is 500 μm or less. [6] The multilayer film according to any one of [1] to [5], wherein the multilayer film has been irradiated with an electron beam under conditions of an absorbed dose of 13 to 300 kGy. [7]. A multilayer film according to any one of [1] to [6], wherein the flexible layer comprises a polyethylene resin. [8]. A multilayer film according to any one of [1] to [7], wherein the ratio of the thickness of the follow layer to the thickness of the multilayer film is 10% or more. [9]. A multilayer film according to 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, was 0.2 N / mm². 2 More than 3N / mm 2 A multilayer film as described in any one of the following items [1] to [9].

[11] A package comprising a multilayer film as described in any one of [1] to

[10] .

[12] The packaging according to

[11] , wherein the packaging is a skin pack packaging.

[13] . A method for manufacturing a package in which contents are packaged by a lid material and a bottom material, the method including: a step of disposing the contents on the bottom material; a step of disposing the lid material on a region of the bottom material that covers the contents and its periphery; a step of bringing the lid material into contact with the contents while heating the lid material to 90 to 250°C, shaping the lid material along the contents, and bonding a portion of the lid material that is in contact with the bottom material to the bottom material, thereby packaging the contents with the lid material and the bottom material, wherein the lid material is composed of the multilayer film according to any one of [1] to

[10] .

Advantages of the Invention

[0008] The multilayer film of the present invention is configured by laminating a sealant layer, a follow layer, and a flexible layer in their thickness directions, the ratio of the thickness of the flexible layer to the thickness of the multilayer film is 2 to 30%, 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 or more and 3.6 N / mm 2 or less, and the oxygen permeability of the multilayer film under the conditions of a temperature of 23°C and a relative humidity of 60%, measured in accordance with JIS K 7126-2:2006, is more than 100 cc / (m 2 ·day·atm). Therefore, it can maintain the quality of the contents, has excellent followability to the contents, and can follow the contents softly.

[0009] In addition, since the package of the present invention includes the above multilayer film, it can maintain the quality of the contents, has excellent followability to the contents, and can follow the contents softly.

Brief Description of the Drawings

[0010] [Figure 1] It is a cross-sectional view schematically showing an example of a multilayer film according to an embodiment of the present invention. [Figure 2] It is a cross-sectional view schematically showing an example of a package according to an embodiment of the present invention. [Modes for carrying out the invention]

[0011] <<Multilayer film (lid material)>> A 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 ratio of the thickness of the flexible layer, the tensile strength, and the oxygen permeability described later.

[0012] Under conditions of a temperature of 23°C and a relative humidity of 60%, the oxygen permeability of the multilayer film (lid material) is 100 cc / (m²). 2 (The oxygen permeability of multilayer film is greater than 100cc / (m)) 2 ·day·atm)). The oxygen permeation amount is 100cc / (m 2 By exceeding the (day·atm) threshold, the quality of the contents can be maintained.

[0013] Under conditions of a temperature of 23°C and a relative humidity of 60%, the oxygen permeability of the multilayer film (lid material) is 110 cc / (m²). 2 It is preferable that it be 120cc / (m) or more, and 120cc / (m 2 It is more preferable that it be 130cc / (m) or more, and 130cc / (m 2 It is even more preferable that it be 140cc / (m) or more, and 140cc / (m 2 It is particularly preferable that the pressure be 150cc / (m³) or higher, for example, 150cc / (m³). 2 It may be greater than or equal to the following (day·atm). By having the oxygen permeability rate equal to or greater 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 5000 cc / (m³). 2 It is preferable that it be less than or equal to 4900cc / (m³). 2 It is more preferable that it be less than or equal to 4800cc / (m²) days·atm. 2 It is even more preferable that it be less than or equal to 4700cc / (m²) days·atm.2 It is particularly preferable that it be less than or equal to (day·atm), for example, 4600cc / (m 2 It may be less than or equal to the above upper limit (day·atm). By keeping the oxygen permeability below the above upper limit, the excessive proliferation of aerobic bacteria inside the pack can be suppressed.

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

[0016] The oxygen permeability of the multilayer film (lid material) can be more easily adjusted, for example, by adjusting the type and amount of components contained in the flexible layer, the thickness and proportion of the flexible layer, etc., as described later.

[0017] For example, in the case of skin pack packaging for food, a gas barrier layer is sometimes provided in the multilayer film that makes up the skin pack packaging to prevent oxidative deterioration of the food. However, for example, foods such as chicken contain anaerobic bacteria such as lactic acid bacteria, and if the barrier function of the gas barrier layer is too high, the growth of anaerobic bacteria is not suppressed, and the carbon dioxide released by the anaerobic bacteria becomes trapped inside the skin pack packaging, causing the putrid odor of carbon dioxide to adhere to the food and degrade the taste of the food. In addition, foods such as chicken have a translucent pink color when fresh, but if the barrier function of the gas barrier layer is too high, it becomes difficult for oxygen to enter from the outside of the skin pack packaging, and the food discolors due to lack of oxygen.

[0018] In contrast, the packaging body constructed using the multilayer film 1 of this embodiment has improved these problems. The reason is that, under conditions of a temperature of 23°C and a relative humidity of 60%, the oxygen permeability of the multilayer film (lid material) is 100 cc / (m³). 2Because the temperature is above (day·atm), the growth of anaerobic bacteria is suppressed, and even if anaerobic bacteria release carbon dioxide, the carbon dioxide is released to the outside of the skin pack packaging, preventing the putrid odor of carbon dioxide from adhering to the food. In addition, oxygen can easily enter from the outside of the skin pack packaging, which suppresses discoloration of the food due to lack of oxygen. Thus, the packaging constructed using the multilayer film 1 of this embodiment can maintain the quality of its contents.

[0019] The temperature at which a displacement of 2000 μm occurs during thermomechanical analysis (TMA) of the multilayer film (lid material) is preferably 120°C or higher, more preferably 120 to 200°C, even more preferably 123 to 190°C, and may be, for example, 130 to 190°C. A temperature above the lower limit further improves the heat resistance of the multilayer film. A temperature below the upper limit further suppresses excessive heat resistance of the multilayer film.

[0020] During 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, for example, 50 to 350 μm, 55 to 340 μm, and 55 to 250 μm. When the displacement is below the upper limit, the melt tension of the multilayer film is further improved, and as a result, the conformability of the multilayer film to its contents is further improved. When the displacement is above the lower limit, excessive melt tension of the multilayer film is further suppressed.

[0021] The thermomechanical analysis of the multilayer film can be performed in accordance with JIS K 7196 by measuring the thermal expansion of the sample from the difference in thermal expansion when a standard sample and the sample to be analyzed are heated at a constant rate. Thermomechanical analysis of multilayer films can be performed, for example, by using a sample with 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 film flow direction (MD).

[0022] During thermomechanical analysis of the multilayer film, the temperature at which a displacement of 2000 μm occurs 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 more easily adjusted by adjusting the conditions of electron beam irradiation to the outer layer, conforming layer, and flexible layer within the multilayer film.

[0023] The multilayer film is preferably irradiated with an electron beam at an absorbed dose of 13 to 300 kGy, more preferably at an absorbed dose of 15 to 250 kGy, and may also be irradiated with an electron beam at any of the following conditions: absorbed dose of 20 to 250 kGy, 45 to 250 kGy, or 70 to 250 kGy. By having the absorbed dose within this range, it is easier to obtain a multilayer film in which, during thermomechanical analysis of the multilayer film, the temperature at which a displacement of 2000 μm occurs and the displacement at 100°C are both within the above numerical ranges. On the other hand, by having the absorbed dose above the lower limit, the crosslinking density of the multilayer film (especially the outer layer, follow-up layer, and flexible layer in this multilayer film) is further improved, resulting in improved heat resistance and melt tension, and improved conformability to the contents of the multilayer film as a whole. By having the absorbed dose below the upper limit, the excessive strength of the multilayer film is further suppressed.

[0024] The reason why electron beam irradiation improves the crosslinking density of the multilayer film (particularly the outer layer, follow-up layer, and flexible layer within the multilayer film) is not clear, but it is speculated as follows: When the multilayer film is irradiated with an electron beam, carbon-hydrogen bonds in the resin (e.g., polyethylene, ionomer) are broken, and radicals are generated at the broken bond ends. It is speculated that the generated radicals, through the molecular motion of their molecular chains, come into contact with molecular chains of other resins (e.g., other polyethylene molecular chains, other ionomer molecular chains), extract hydrogen atoms, and bond with carbon atoms in the molecular chains of the other resins (e.g., other polyethylene molecular chains, other ionomer molecular chains), resulting in the formation of a crosslinked structure.

[0025] The acceleration 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 having the acceleration voltage during electron beam irradiation within this range, it becomes easier to obtain a multilayer film in which, during thermomechanical analysis of the multilayer film, the temperature at which a displacement of 2000 μm occurs and the displacement at 100°C are both within the above numerical ranges. On the other hand, by having the acceleration voltage during electron beam irradiation above the lower limit, the crosslinking density of the multilayer film (especially the outer layer, follow-up layer, and flexible layer within the multilayer film) is further improved, resulting in improved heat resistance and melt tension, and improved conformability to the contents of the multilayer film as a whole. By having the acceleration voltage during electron beam irradiation below the upper limit, excessive strength of the multilayer film is further suppressed.

[0026] The gel fraction of the multilayer film is preferably 30% or more, more preferably 30-90%, and even more preferably 32-85%, and may be, for example, 40-82%, 48-82%, and 55-82%. When the gel fraction of the multilayer film is above 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 below the upper limit, the excessive strength of the multilayer film is further suppressed.

[0027] The gel fraction of the multilayer film can be measured in accordance with JIS K 6769 by utilizing 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, the insoluble film remaining without dissolving is dried, and then the mass of the resulting dried product is measured. The gel fraction can then be calculated from the mass of the multilayer film before dissolution and the mass of the dried insoluble film. More specifically, for example, a multilayer film (mass Xg) is wrapped in a stainless steel mesh (mass Yg), immersed in a heated solvent, and then the multilayer film wrapped in the stainless steel mesh (in other words, the insoluble film) is removed. Next, it is vacuum-dried, and the mass (Zg) of the multilayer film wrapped in the stainless steel mesh (in other words, the insoluble film) after drying is measured. Then, the following formula (1): Gel fraction (mass%) of multilayer film = (ZY) / X × 100 (1) The gel fraction of the multilayer film is calculated using this method.

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

[0029] Preferably, the multilayer film satisfies either one of the above-mentioned conditions: a temperature at which a displacement of 2000 μm is observed during thermomechanical analysis, and a gel fraction, or both conditions. That is, examples of the multilayer film include: one at which the temperature at which a displacement of 2000 μm is observed during thermomechanical analysis is 120°C or higher and the gel fraction is less than 30%; one at which the temperature at which a displacement of 2000 μm is observed during thermomechanical analysis is less than 120°C and the gel fraction is 30% or higher; and one at which the temperature at which a displacement of 2000 μm is observed during thermomechanical analysis is 120°C or higher and the gel fraction is 30% or higher. However, generally, the multilayer film is more preferably one that satisfies both of the above conditions, namely, one at which the temperature at which it exhibits a displacement of 2000 μm during thermomechanical analysis is 120°C or higher, and one with a gel fraction of 30% or higher.

[0030] The tensile strength of the multilayer film (lid material) at a temperature of 140°C is 0.2 N / mm². 2 More than 3.6N / mm 2 The following applies: The tensile strength is 0.2 N / mm 2 As a result, the conformability of the lid material to the contents can be improved. Consequently, dripping that occurs during storage is suppressed, preventing the leakage of flavor components and allowing for long-term storage without a decline in taste. The tensile strength is 3.6 N / mm². 2 The following allows for packaging 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 / mm². 2 More than 3N / mm 2 Preferably, it is 0.2 N / mm 2 More than 2.9N / mm 2 It is more preferable that the following is the case: 0.2 N / mm 2 More than 2.8N / mm 2 It is even more preferable that the following conditions apply, for example, 0.2 N / mm 2 The above is 2.7 N / mm². 2The following conditions may also apply. If the tensile strength is equal to or greater than the lower limit, the conformability of the lid material to the contents can be further improved. If the tensile strength is equal to or less than the upper limit, the contents can be packaged without compressing their shape as much.

[0032] The tensile strength of the multilayer film (lid 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 (Shimadzu Corporation's "Constant Temperature Bath Tensile Testing Device AGS-X"). The measurement conditions can be, for example, a tensile speed of 500 mm / min.

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

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

[0035] At a temperature of 140°C, the dynamic modulus E' of the multilayer film (lid material) is 1 × 10⁻⁶ 4 Pa or more 1×10 7 It is preferable that the dynamic modulus E' is Pa or less. If the dynamic modulus E' is above the lower limit, the conformability of the lid material to the contents can be further improved. If the dynamic modulus E' is below the upper limit, the contents can be packaged without compressing their shape as much.

[0036] At a temperature of 140°C, the dynamic modulus E' of the multilayer film (lid material) is 1.1 × 10⁻⁶. 4 Pa or more 9.9×10 6 It is more preferable that it be less than or equal to Pa, and 1.2 × 10 4 Pa or more 9.8×10 6 It is even more preferable that it be less than or equal to Pa, 1.3 × 10 4Pa or more 9.7×10 6 It is particularly preferable that it be less than or equal to Pa, for example, 1.4 × 10⁻⁶ 4 Pa or more 9.6×10 6 It may be less than or equal to Pa. If the dynamic modulus E' is greater than or equal to the lower limit, the conformability of the lid material to the contents can be further improved. If the dynamic modulus E' is less than or equal to the upper limit, the contents can be packaged without compressing their shape as much.

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

[0038] When the crosslinking density of the multilayer film (lid material) is improved, the heat resistance and melt tension of the multilayer film (lid material) are improved, as is the dynamic modulus E'. Therefore, the dynamic modulus 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 modulus E' of the multilayer film (lid material) can be more easily adjusted by adjusting the thickness and proportion of the flexible layer.

[0040] The thickness of the multilayer film (lid material) is preferably 60 μm or more, more preferably 70 to 400 μm, even more preferably 80 to 300 μm, and may be, for example, 100 to 200 μm. When the thickness of the multilayer film is above the lower limit, the strength of the multilayer film is further improved. When the thickness of the multilayer film is below the upper limit, the excessive thickness of the multilayer film is further suppressed.

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

[0042] In the aforementioned multilayer film (lid material), regardless of its type, all layers are transparent, and it is preferable that the multilayer film is transparent, that is, that the multilayer film is a transparent multilayer film. In a package made using such a multilayer film, the contents can be easily seen through the multilayer film (lid material).

[0043] The more detailed composition of the aforementioned multilayer film (lid material) and its manufacturing method will be described separately.

[0044] The present invention will be described in more detail below with reference to the drawings. Note that, for convenience in making the features of the present invention easier to understand, the drawings may show enlarged versions of key parts, and the dimensional ratios of each component may not be the same as those in reality.

[0045] Figure 1 is a schematic cross-sectional view showing an example of the multilayer film (laminated film) among the multilayer film (lid material) in this embodiment. The multilayer film 1 shown here is constructed by laminating a sealant layer 11, a follow-up layer 13 (more specifically, a first follow-up layer 131), and a flexible layer 14 in this order in the thickness direction.

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

[0047] <Sealant layer> The sealant layer 11 may contain polyethylene-based resins such as ethylene-vinyl acetate copolymer (EVA), polyethylene, ionomer, or polyethylene copolymer (referred to as "polyethylene-based resin in the sealant layer" in this specification). The inclusion of a polyethylene-based resin in the sealant layer 11 improves the easy-peel properties of the multilayer film 1 by creating pseudo-adhesion to the adherend.

[0048] In this specification, "polyethylene resin" means a resin having at least structural units derived from ethylene, which 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 polyethylene resin in the sealant layer (i.e., it may consist only of polyethylene resin in the sealant layer), or it may contain polyethylene resin in the sealant layer and other components (which may be referred to as "other components" in this specification) (i.e., it may consist of polyethylene resin in the sealant layer and the other components).

[0050] The other components included in the sealant layer 11 are not particularly limited and can be arbitrarily selected depending on the purpose, and may be, for example, resin components and non-resin components. The other 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 monomer, or a copolymer, which is a polymer of two or more monomers.

[0051] Other non-resin components include, for example, additives known in the art. Examples of the aforementioned additives include antioxidants, antistatic agents, nucleating agents, inorganic particles, viscosity reducers, viscosity enhancers, heat stabilizers, lubricants, infrared absorbers, and ultraviolet absorbers.

[0052] The other components contained in the sealant layer 11 may consist of only one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0053] In the sealant layer 11, the ratio of polyethylene resin content in the sealant layer to the total mass of the sealant layer 11 is preferably 65 to 100% by mass, more preferably 70 to 100% by mass, and even more preferably 75 to 100% by mass, and may be, for example, 85 to 100% by mass. When the ratio is above the lower limit, the easy-peel properties due to the emergence of pseudo-adhesion with the adherend are further improved. The aforementioned ratio is typically the same as the ratio of the content (parts by mass) of polyethylene resin in the sealant layer to the total content (parts by mass) of components that do not vaporize at room temperature in the sealant layer forming composition described later.

[0054] In this specification, "room temperature" means a temperature that is neither cooled nor heated, i.e., a normal temperature, such as 15-25°C.

[0055] The sealant layer 11 may consist of one layer (single layer) or of two or more layers. If the sealant layer 11 consists of multiple layers, these layers may be identical or different, and the combination of these 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 identical or different from one another" means "all layers may be identical, all layers may be different, or only some layers may be identical," and further, "multiple layers are different from one another" means "at least one of the constituent materials and thickness of each layer is different from the 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 even more preferably 10 to 90 μm. For example, it may be any of 10 to 70 μm, 10 to 50 μm, and 10 to 30 μm. When the thickness of the sealant layer 11 is greater than or equal to the lower limit, the strength of the sealant layer 11 is increased. When the thickness of the sealant layer 11 is less than or equal to the upper limit, the thickness of the sealant layer 11 is suppressed, and the seal strength is increased when the multilayer film 1 is sealed by heating. Here, "thickness of sealant layer 11" refers to the total thickness of the sealant layer 11. For example, the thickness of a sealant layer 11 consisting of multiple layers refers to the total thickness of all the layers that make up the 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 6-80%, and even more preferably 7-75%. When the ratio is above 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 below the upper limit, the excessive thickness of the sealant layer 11 is further suppressed, and the seal strength is enhanced when the multilayer film 1 is sealed by heating.

[0059] When the sealant layer is made of ethylene-vinyl acetate copolymer (EVA) or has ethylene-vinyl acetate copolymer (EVA) as its main component, increasing its thickness allows it to also function as a follow-up layer.

[0060] The 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 the 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) (in this specification, the polyolefin resin and the polyester resin may be referred to as "outer layer resin"). By containing the outer layer resin in the outer layer 12, the crosslinking 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 its contents is further improved.

[0062] The outer layer 12 may contain only the outer layer resin (i.e., it may consist solely of the outer layer resin), or it may contain the outer layer resin and other components (which may be 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), and high-density polyethylene (HDPE). Of these, low-density polyethylene (LDPE) is preferred. Examples of low-density polyethylene include those with a density of 0.945 g / cm³. 3 The following low-density polyethylene is preferred, with a density of 0.943 g / cm³. 3 It is more preferable that the low-density polyethylene has a density of 0.941 g / cm³. 3 It is even more preferable that the polyethylene is low-density polyethylene. By including such low-density polyethylene (LDPE), the crosslinking density of the outer layer 12 can be further improved by irradiating the multilayer film 1 with an electron beam from the outside of the outer layer 12. As a result, the conformability of the multilayer film 1 to its contents is further improved.

[0064] The outer layer resin contained in the outer layer 12 may be of only one type, or it may be of two or more types. If there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0065] The other components included in the outer layer 12 are not particularly limited and can be arbitrarily selected depending on the purpose, and may be, for example, resin components and non-resin components. The other components, which are resin components, are resins other than the resin in the outer layer.

[0066] The other components contained in the outer layer 12 may consist of only one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0067] The ratio of the resin content in the outer layer 12 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. For example, it may be any of 70 to 100% by mass and 85 to 100% by mass. By having the ratio be equal to or greater than the lower limit, the crosslinking density of the outer layer 12 can be further improved by irradiating the multilayer film 1 with an electron beam from the outside of the outer layer 12. As a result, the conformability of the multilayer film 1 to its contents is further improved. The aforementioned ratio is typically 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 outer layer forming composition described later.

[0068] The outer layer 12 may consist of one layer (single layer) or of two or more layers. If the outer layer 12 consists of multiple layers, these layers may be identical or different, and the combination of these 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 even more preferably 10 to 140 μm. For example, it may be any of 10 to 110 μm, 10 to 100 μm, 10 to 90 μm, 10 to 80 μm, and 10 to 70 μm. If the thickness of the outer layer 12 is greater than or equal to the lower limit, the crosslinking density of the outer layer 12 can be further improved by irradiating the multilayer film 1 with an electron beam from the outside of the outer layer 12 side. If the thickness of the outer layer 12 is less than or equal to the upper limit, the thickness of the outer layer 12 is prevented from becoming excessive. Here, "thickness of outer layer 12" refers to the total thickness of the outer layer 12. For example, the thickness of an outer layer 12 consisting of multiple layers refers to the total thickness of all the 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 12-88%, and even more preferably 14-86%. When the ratio is above the lower limit, the effect obtained by irradiating the multilayer film 1 with an electron beam from the outside of the outer layer 12 is enhanced. When the ratio is below the upper limit, the thickness of the outer layer 12 is prevented from becoming excessive.

[0071] <Follower layer> The follow-up layer 13 may contain polyolefin resins such as ionomers (ION) and ethylene-vinyl acetate copolymers (EVA). Of these, it is preferable that it contains an ionomer. The aforementioned ionomer refers to a copolymer of ethylene and a small amount of acrylic acid or methacrylic acid, in which an ionic bridged structure is formed by salt formation between the acidic portion and metal ions.

[0072] Examples of the aforementioned metal ions include sodium ions and zinc ions. In this specification, ionomers in which the metal ion is a sodium ion are sometimes referred to as sodium-based ionomers, and ionomers in which the metal ion is a zinc ion are sometimes referred to as zinc-based ionomers.

[0073] The conforming layer 13 may contain polyethylene-based resins other than ionomer, such as ethylene-vinyl acetate copolymer (EVA), polyethylene, or polyethylene copolymer (in this specification, the ionomer and the polyethylene-based resin may be referred to as "polyethylene-based resin in the conforming layer"). By containing polyethylene-based resin in the conforming layer 13, the crosslinking density of the conforming layer 13 can be improved when the multilayer film 1 is irradiated with an electron beam. As a result, the conformability of the packaging made using the multilayer film 1 to its contents is further improved.

[0074] The follow-up layer 13 may consist of one layer (single layer) or of two or more layers. If the follow-up layer 13 consists of multiple layers, these layers may be the same or different from each other, and the combination of these layers is not particularly limited as long as it does not impair the effects of the present invention.

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

[0076] The follow-up layer 13 may contain only an ionomer (i.e., it may consist of an ionomer), or it may contain an ionomer and other components (which may be referred to as "other components" in this specification) (i.e., it may consist of an ionomer and the other components).

[0077] The ionomer contained in the follow-up layer 13 may be one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0078] The other components included in the follow-up layer 13 are not particularly limited and can be arbitrarily selected depending on the purpose, and may be, for example, resin components and non-resin components. The other components, which are resin components, are resins other than ionomers.

[0079] The other components contained in the follow-up layer 13 may consist of only one type or two or more types. If there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0080] The ratio of ionomer content in the follow-up layer 13 to the total mass of the follow-up 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, for example, it may be any of 70 to 100% by mass and 85 to 100% by mass. By having the ratio be equal to or greater than the lower limit, the crosslinking density of the follow-up 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 conformability of the multilayer film 1 to its contents is further improved. The aforementioned ratio is typically the same as the ratio of the ionomer content (parts by mass) to the total content (parts by mass) of components that do not vaporize at room temperature in the follow-up layer forming composition described later.

[0081] The thickness of the follow-up layer 13 (the thickness of the first follow-up layer 131 and the second follow-up layer 132, respectively) is preferably 4 to 146 μm, more preferably 7 to 143 μm, and even more preferably 10 to 140 μm. For example, it may be any of 10 to 110 μm, 10 to 80 μm, 10 to 50 μm, and 10 to 30 μm. If the thickness of the follow-up layer 13 is greater than or equal to the lower limit, the crosslinking density of the follow-up 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 conformability of the multilayer film 1 to its contents is further improved. If the thickness of the follow-up layer 13 is less than or equal to the upper limit, the thickness of the follow-up layer 13 is prevented from becoming excessive. Here, "thickness of the follow-up layer 13" refers to the total thickness of the follow-up layer 13 (for example, the total thickness of the follow-up layer 13 located between the sealant layer 11 and the first adhesive layer 151, or the total thickness of the follow-up layer 13 located between the second adhesive layer 152 and the outer layer 12). For example, the thickness of a follow-up layer 13 consisting of multiple layers refers to the total thickness of all the layers that make up the follow-up 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 11-89%, and even more preferably 12-88%. When the ratio is above the lower limit, the effect obtained by irradiating the multilayer film 1 with an electron beam is enhanced. When the ratio is below the upper limit, the thickness of the follow-up layer 13 is prevented from becoming excessive.

[0083] If the follow-through layer is made of ionomer (ION) or has ionomer (ION) as its main component, increasing its thickness will allow it to function as an outer layer as well.

[0084] <Flexible layer> The flexible layer 14 improves the flexibility of the multilayer film 1 and also improves the conformability of the multilayer film 1 to its contents.

[0085] The flexible layer 14 may contain polyethylene-based resins such as polyethylene, ionomer, ethylene-vinyl acetate copolymer (EVA), ethylene-methacrylic acid copolymer (EMAA), ethylene methacrylate copolymer (EMMA), and other polyethylene copolymers, or polyamide-based resins such as nylon (which may be referred to as "resin in the flexible layer" in this specification). The inclusion of the resin in the flexible layer 14 improves the flexibility of the multilayer film 1 and further increases the crosslinking density of the flexible layer 14 when the multilayer film 1 is irradiated with an electron beam. As a result, the conformability of the multilayer film 1 to its contents is further improved.

[0086] The resin in the flexible layer is preferably a resin other than ethylene-vinyl alcohol copolymer (EVOH, also known as ethylene-vinyl acetate copolymer saponified). By using such a resin in the flexible layer, the oxygen permeability of the multilayer film (lid material) under conditions of a temperature of 23°C and a relative humidity of 60% can be reduced to 100 cc / (m²). 2 It becomes easier to adjust to the day / atm limit.

[0087] The flexible layer 14 may contain only the resin in the flexible layer (i.e., it may consist only of the resin in the flexible layer), or it may contain the resin in the flexible layer and other components (which may be 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 included in the flexible layer 14 are not particularly limited and can be arbitrarily selected depending on the purpose, and may be, for example, resin components and 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 monomer, or a copolymer, which is a polymer of two or more monomers.

[0089] Other non-resin components include, for example, the same additives mentioned earlier as other components of the sealant layer 11.

[0090] The other components contained in the flexible layer 14 may be one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0091] The ratio of the resin content in the flexible layer 14 to the total mass of the flexible layer 14 is preferably 50 to 100% by mass, more preferably 60 to 100% by mass, and even more preferably 70 to 100% by mass, and may be, for example, 85 to 100% by mass. By having the ratio be greater than or equal to the lower limit, the flexibility of the multilayer film 1 is further improved, and by irradiating the multilayer film 1 with an electron beam from the outside on the outer layer 12 side, the crosslinking density of the flexible layer 14 can be further improved. As a result, the conformability of the multilayer film 1 to its contents is further improved. The aforementioned ratio is typically 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 flexible layer forming composition described later.

[0092] The ratio of the ethylene-vinyl alcohol copolymer content in the flexible layer 14 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. For example, it may be 0% by mass (the flexible layer 14 may not contain ethylene-vinyl alcohol copolymer). When the ratio is below the upper limit, the oxygen permeability of the multilayer film (lid material) under conditions of a temperature of 23°C and a relative humidity of 60% becomes greater. The aforementioned ratio is typically the same as the ratio of the ethylene-vinyl alcohol copolymer content (parts by mass) to the total content (parts by mass) of components that do not vaporize at room temperature in the flexible layer forming composition described later.

[0093] The flexible layer 14 may consist of one layer (single layer) or of two or more layers. If the flexible layer 14 consists of multiple layers, these layers may be identical or different, and the combination of these 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 even more preferably 2 to 80 μm, for example, it may be any of 4 to 60 μm, 4 to 40 μm, and 4 to 20 μm. By having a thickness of the flexible layer 14 greater than or equal to the lower limit, the flexibility of the multilayer film 1 is further improved, and by irradiating the multilayer film 1 with an electron beam from the outside of the outer layer 12, the crosslinking density of the flexible layer 14 can be further improved. As a result, the conformability of the multilayer film 1 to its contents is further improved. By having a thickness of the flexible layer 14 less than or equal to the upper limit, the tensile strength of the multilayer film 1 at a temperature of 140°C is 3.6 N / mm². 2 The following can be done, and the shape of the packaged contents can be better preserved. Here, "thickness of the flexible layer 14" refers to the total thickness of the flexible layer 14. For example, the thickness of a flexible layer 14 consisting of multiple layers refers to the total thickness of all the layers that make up the flexible layer 14.

[0095] The ratio of the thickness of the flexible layer 14 to the thickness of the multilayer film 1 is 2-30%. By keeping this ratio above the lower limit, layer breakage of the flexible layer can be suppressed. In this specification, "layer breakage of the flexible layer" means that a portion of the flexible layer is not formed in the multilayer film, which occurs, for example, when the thickness of the flexible layer is too thin. By keeping this ratio below the upper limit, the tensile strength of the multilayer film 1 at a temperature of 140°C is 3.6 N / mm². 2 The following is possible, 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 above the lower limit, the tearing of the flexible layer can be further suppressed. When the ratio is below the upper limit, the tensile strength of the multilayer film 1 at a temperature of 140°C is 3.6 N / mm². 2 The following can be done, and the shape of the packaged contents can be better preserved.

[0097] For example, since many foods such as chicken are generally irregular in shape, there was a problem in that the conformability of skin pack packaging to the food (the ability to adhere tightly without causing wrinkles) was reduced.

[0098] In contrast, the packaging body constructed using the multilayer film 1 of this embodiment, which comprises an outer layer 12, a conforming layer 13, and a flexible layer 14, overcomes these problems. This is because the presence of the outer layer 12, the conforming layer 13, and the flexible layer 14 improves the heat resistance, melt tension, and tensile strength of the multilayer film 1, resulting in excellent conformability to the contents.

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

[0100] The adhesive contained in the adhesive layer 15 is not particularly limited, as long as it can bond the two layers to be bonded with sufficient strength. Examples of adhesives include adhesive resins such as olefin resins (i.e., polymers of olefins which are one or more monomers).

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

[0102] Examples of the ethylene-based copolymer contained in the adhesive layer 15 include copolymers of ethylene and vinyl group-containing monomers. Examples of copolymers of ethylene and vinyl group-containing monomers include maleic anhydride graft-modified 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. Examples of the ionomer mentioned above include the same ionomer previously listed as being included in the follower layer 13.

[0103] Examples of the propylene copolymer contained in the adhesive layer 15 include a copolymer of propylene and a vinyl group-containing monomer. Examples of copolymers of propylene and vinyl group-containing monomers include maleic anhydride graft-modified linear low-density polypropylene and propylene-based thermoplastic elastomers.

[0104] Examples of the butene-based 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 (modified copolymers) of these copolymers.

[0105] The adhesive layer 15 may contain only an adhesive (i.e., consist of an adhesive), or it may contain an adhesive and other components (which may be 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. If there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

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

[0108] The other components contained in the adhesive layer 15 may consist of only one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0109] The ratio of the adhesive content in the adhesive layer 15 to the total mass of the adhesive layer 15 may be, for example, 50 to 100% by mass. The aforementioned ratio is typically 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 adhesive layer-forming composition described later.

[0110] The adhesive layer 15 may consist of one layer (single layer) or of two or more layers. If the adhesive layer 15 consists of multiple layers, these layers may be the same or different from each other, and the combination of these 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 (the thickness of the first adhesive layer 151 and the second adhesive layer 152, respectively) is preferably 4 to 96 μm, more preferably 7 to 93 μm, and may be, for example, 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 greater than or equal to the lower limit, the adhesive strength of the two layers to be bonded is increased. When the thickness of the adhesive layer 15 is less than or equal to the upper limit, the thickness of the adhesive layer 15 is prevented from becoming excessive. Here, "thickness of adhesive layer 15" refers to the total thickness of the adhesive layer 15 (for example, the total thickness of the adhesive layer 15 placed between the pinhole-resistant layer 16 and the flexible layer 14, or the total thickness of the adhesive layer 15 placed between the flexible layer 14 and the conforming layer 13). For example, the thickness of an adhesive layer 15 consisting of multiple layers refers to the total thickness of all the layers that make up the adhesive layer 15.

[0112] <Other layers> The multilayer film 1 may also include other layers that do not fall under 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 types and placement positions of the other layers are not particularly limited and can be arbitrarily selected according to the purpose.

[0114] The other layers provided in the multilayer film 1 may consist of only one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0115] Each of the aforementioned other layers may consist of one layer (single layer) or two or more layers. If the aforementioned other layers consist of multiple layers, these layers may be identical or different, and the combination of these layers is not particularly limited as long as it does not impair the effects of the present invention.

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

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

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

[0119] The multilayer film in this embodiment is not limited to those described above, and some components may be modified, deleted, or added without departing from the spirit of the present invention. For example, the multilayer film may not include one or two of the outer layer and the adhesive layer. However, it is preferable that the multilayer film comprises a sealant layer, a conforming layer, an adhesive layer, a flexible layer, an adhesive layer, a conforming layer, and an outer layer in this order, as shown in Figure 1.

[0120] <<Manufacturing method for multilayer film (lid material)>> The aforementioned multilayer film (lid material) can be manufactured by known methods depending on its type. For example, laminated films such as the multilayer film can be manufactured by a feed block method in which resins or resin compositions that form 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] Furthermore, the laminated film can also be manufactured by coating the surface of another layer that constitutes the laminated film with a resin or resin composition that will be the forming material for any of the layers within it, drying it as necessary to form the laminated structure within the laminated film, and further laminating other layers as necessary to achieve the desired arrangement.

[0122] Furthermore, the laminated film can also be manufactured by separately preparing two or more films in advance to form any two or more of the layers, laminating these films together using an adhesive by one of the following methods: dry lamination, extrusion lamination, hot melt lamination, or wet lamination, and further laminating other layers as needed to achieve the desired arrangement. In this case, an adhesive capable of forming the adhesive layer may be used.

[0123] Furthermore, the laminated film can also be manufactured by laminating two or more films that have been prepared separately in advance, without using adhesive, using a thermal lamination method or the like, and then further laminating other layers as needed to achieve the desired arrangement.

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

[0125] Regardless of the manufacturing method, the resin composition that forms any of the layers in the laminated film can be manufactured by adjusting the types and amounts of the constituent components so that the layer to be formed contains the desired components (constituent materials) in the desired amounts. For example, the ratio of the amounts of components that do not vaporize at room temperature in the resin composition is usually the same as the ratio of the amounts of those components in the layer formed from this resin composition.

[0126] Examples of resin compositions for forming a sealant layer (sealant layer 11 in the multilayer film 1 shown in Figure 1) include those comprising a polyethylene resin in the sealant layer and, if necessary, the other components.

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

[0128] Examples of resin compositions for forming a follow-up layer (in the multilayer film 1 shown in Figure 1, the follow-up layer 13) include those comprising a polyethylene-based resin in the follow-up layer and, if necessary, the other components.

[0129] Examples of resin compositions for forming a flexible layer (flexible layer 14 in the multilayer film 1 shown in Figure 1) (sometimes referred to as "flexible layer forming composition" in this specification) include those comprising the resin in the flexible layer and, if necessary, the other components.

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

[0131] The multilayer film 1 can be used as a lid material. The packaging of this embodiment can be manufactured by heat-sealing this lid material and the bottom material.

[0132] <<Bottom material>> The aforementioned bottom material has an oxygen permeability of 100 cc / (m³). 2 It is not particularly limited as long as it is greater than (day·atm) and can be used as a base material for packaging. The aforementioned base material may be one of known types.

[0133] Under conditions of a temperature of 23°C and a relative humidity of 60%, the oxygen permeability of the bottom material is 110 cc / (m³). 2 It is preferable that the pressure be 130cc / (m³) or higher, for example, 130cc / (m³). 2 ·day · atm) or more, 120cc / (m 2 ·day · atm) or more, 140cc / (m 2 ·day · atm) or more, and 150cc / (m 2 Any of the above (day, ATM) is acceptable. On the other hand, the oxygen permeability is 5000 cc / (m³). 2 It is preferable that it be less than or equal to (day·atm), 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) Any of the following may be acceptable.

[0134] Under conditions of a temperature of 23°C and a relative humidity of 60%, the oxygen permeability of the bottom material can be measured in accordance with JIS K 7126-2:2006.

[0135] The oxygen permeability of the substrate can be more easily adjusted by, for example, adjusting the type and amount of components contained in the substrate, the thickness of the substrate, 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. The strength of the base material is further improved when the thickness of the base material is greater than or equal to the lower limit. The thickness of the base material is preferably 6000 μm or less. By keeping the thickness of the base material below the above upper limit, the thickness of the base material is prevented from becoming excessive. The thickness of the base material can be adjusted as appropriate within a range set by any combination of the lower and upper limits mentioned above.

[0137] In the case of the base material, regardless of its type, 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 made with a transparent base material, the contents can be easily seen through the base material.

[0138] The detailed composition of the base material and its manufacturing method will be explained separately.

[0139] <<One embodiment of the base material>> The base material is preferably a laminated body composed of multiple layers stacked together. A preferred laminated base material is, for example, a resin laminate comprising a foamed resin layer and a non-foamed resin layer provided on the foamed resin layer.

[0140] The foamed resin layer may be of known origin. Examples of the foamed resin layer include a resin layer containing a foamed polystyrene resin (PSP).

[0141] The density of the foamed resin layer is not particularly limited, but is generally 0.05 to 0.5 g / cm³. 3 It is preferable that this be the case. The foaming ratio of the foamed resin layer is not particularly limited, but is preferably 2 to 20 times. The thickness of the foamed resin layer is not particularly limited, but is preferably 500 to 6000 μm.

[0142] Examples of the non-foamed resin layers include a multilayer film for base materials, in which an easy-peel layer, a flexible layer, a pinhole-resistant layer, and an adhesive layer are laminated in this order in the thickness direction. In the multilayer film for base materials, 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 multilayer film for the base material may, for example, include an intermediate adhesive layer between the easy-peel layer and the flexible layer for bonding these two layers together. Furthermore, the multilayer film for the base material may include, for example, an intermediate adhesive layer between the flexible layer and the pinhole-resistant layer for bonding these two layers together. In other words, the multilayer film for the base material may be constructed by laminating an easy-peel layer, an intermediate adhesive layer, a flexible 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 between these two intermediate adhesive layers, the intermediate adhesive layer located between the easy-peel layer and the flexible layer may be referred to as the first intermediate adhesive layer, and the intermediate adhesive layer located between the flexible layer and the pinhole-resistant layer may be referred to as the second intermediate adhesive layer, as necessary. These two intermediate adhesive layers (first intermediate adhesive layer, second intermediate adhesive layer) may be the same as or different from each other.

[0145] <Easy Peel Layer> Examples of the easy-peel layer in the multilayer film for base materials include those that exhibit peelability due to cohesive failure. An example of an easy-peel layer that exhibits peelability due to cohesive failure is one that contains two types of incompatible polyolefins.

[0146] Examples of two incompatible polyolefins included in the easy-peel layer of a multilayer film for base materials include an ethylene-based polymer having at least one structural unit derived from ethylene and a propylene-based polymer having at least one structural unit derived from propylene. In other words, the easy-peel layer includes, for example, an ethylene-based polymer having at least structural units derived from ethylene, and a propylene-based polymer having at least structural units derived from propylene.

[0147] Examples of ethylene-based polymers included in the easy-peel layer of a multilayer film for base materials include ethylene homopolymers and ethylene-based copolymers.

[0148] Examples of the ethylene homopolymers 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 copolymer comprises structural units derived from ethylene and structural units derived from monomers 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 ionomers (ION). Examples of the ionomer mentioned above include the same ionomer previously listed as being included in the follow-up layer 13 of the multilayer film 1 described earlier.

[0150] In multilayer films for base materials, the easy-peel layer preferably contains low-density polyethylene as the ethylene-based polymer. The easy-peel properties of such an easy-peel layer are better.

[0151] The propylene-based polymer contained in the easy-peel layer of the multilayer film for base materials includes propylene homopolymers (i.e., polypropylene or homopolypropylene, hPP) and propylene copolymers.

[0152] The propylene copolymer comprises structural units derived from propylene and structural units derived from monomers other than propylene. Examples of the propylene 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] In multilayer films for base materials, the easy-peel layer preferably contains polypropylene as the propylene-based polymer. The easy-peel properties of such an easy-peel layer are better.

[0154] The easy-peel layer in a multilayer film for base materials may contain only one type of component that exhibits easy-peel properties, or it may contain two or more types. If there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose. For example, if the components that exhibit easy-peel properties are the two incompatible polyolefins mentioned above, the easy-peel layer may contain only one type of these polyolefins, or it may contain two or more types.

[0155] In the easy-peel layer of the multilayer film for the base material, the ratio of the content (parts by mass) of the ethylene polymer to the total content (parts by mass) of the ethylene polymer and the propylene polymer is preferably 10 to 90% by mass, and may be, for example, 30 to 90% by mass, 45 to 90% by mass, or 60 to 90% by mass. When the ratio is above the lower limit, the easy-peel properties of the easy-peel layer are improved. When the ratio is below the upper limit, the peel strength is more stable. The aforementioned ratio is typically the same as the ratio of the ethylene polymer content (parts by mass) to the total content (parts by mass) of the ethylene polymer and propylene polymer in the easy-peel layer forming composition for base materials described later.

[0156] The easy-peel layer in a multilayer film for base materials may contain other components besides the components that exhibit easy-peel properties (for example, the two incompatible polyolefins mentioned above), as long as they do not impair the easy-peel properties. The other components contained in the Easy Peel layer may consist of only one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0157] In the easy-peel layer of the multilayer film for base material, the ratio of the content of the component that exhibits easy-peel properties (for example, the ratio of the total content of the two types of incompatible polyolefins mentioned above) to the total mass of the easy-peel layer is preferably 50 to 100% by mass, more preferably 70 to 100% by mass, and may be any of 80 to 100% by mass, 90 to 100% by mass, 95 to 100% by mass, 97 to 100% by mass, and 99 to 100% by mass. The easier-peel properties of the easy-peel layer are improved when the ratio is above the lower limit. The aforementioned ratio is typically the same as the ratio of the content (parts by mass) of the component that exhibits easy-peel properties to the total content (parts by mass) of the component that does not vaporize at room temperature in the easy-peel layer forming composition for base materials described later.

[0158] Other components included in the Easy Peel layer of the multilayer film for base materials include, for example, anti-fogging agents and anti-blocking agents.

[0159] The easy-peel layer in the multilayer film for base material may consist of one layer (single layer) or of two or more layers. When the easy-peel layer consists of multiple layers, these layers may be identical or different, and the combination of these 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 the base material is preferably 2 to 50 μm. When the thickness of the easy-peel layer is above the lower limit, the seal strength of the easy-peel layer is moderately high. When the thickness of the easy-peel layer is below the upper limit, the easy-peel properties are further enhanced. Here, "Easy Peel layer thickness" refers to the total thickness of the Easy Peel layer. For example, the thickness of an Easy Peel layer consisting of multiple layers refers to the total thickness of all the 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 the base material is not particularly limited, but is preferably 5 to 40%. When the ratio is above the lower limit, the seal strength of the easy-peel layer is moderately high. When the ratio is below the upper limit, the easy-peel properties are further enhanced.

[0162] <Flexible layer> The aforementioned flexible layer improves the flexibility of the multilayer film for the base material.

[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. By including the resin in the flexible layer 14, the flexibility of the multilayer film for base material can be further improved.

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

[0165] The flexible layer in the multilayer film for base material may contain only the resin in the flexible layer (i.e., it may consist only of the resin in the flexible layer), or it may contain the resin in the flexible layer and other components (which may be 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 included in the flexible layer of the multilayer film for base material are not particularly limited and can be arbitrarily selected depending on the purpose, and may be, for example, resin components and 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 monomer, or a copolymer, which is a polymer of two or more monomers.

[0167] Other non-resin components include, for example, the same additives mentioned earlier as other components included in the sealant layer 11 of the multilayer film 1 described above.

[0168] The other components contained in the flexible layer of the multilayer film for base material may be one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

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

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

[0171] The flexible layer in the multilayer film for base material may consist of one layer (single layer) or of two or more layers. When the flexible layer consists of multiple layers, these layers may be identical or different, and the combination of these 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 the base material is preferably 2 to 20 μm. A thickness of the flexible layer greater than or equal to the lower limit increases its flexibility. A thickness of the flexible layer less than or equal to the upper limit prevents the flexible layer from becoming excessively thick. Here, "thickness of the flexible layer" refers to the total thickness of the flexible layer. For example, the thickness of a flexible layer consisting of multiple layers refers to the total thickness of all the layers that make up the flexible layer.

[0173] The ratio of the thickness of the flexible layer to the thickness of the multilayer film for the base material is not particularly limited, but is preferably 5 to 15%. When the ratio is above the lower limit, the flexibility of the multilayer film for the base material is increased. When the ratio is below the upper limit, the thickness of the flexible layer is prevented from becoming excessive.

[0174] <Pinhole-resistant layer> The aforementioned pinhole-resistant layer is a layer that protects the structure of the multilayer film used for bottoming materials, such as by suppressing the occurrence of pinholes in the multilayer film used for bottoming materials.

[0175] In the multilayer film for the base material, the pinhole-resistant layer preferably contains a polyolefin resin. Examples of the polyolefin resins 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); and polypropylene.

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

[0177] The other components included in the pinhole-resistant layer of the multilayer film for base material are not particularly limited and can be arbitrarily selected depending on the purpose, and may be, for example, resin components and non-resin components. The other component, which is a resin component, is a resin other than a polyolefin resin. Other non-resin components include, for example, the same additives mentioned earlier as other components included in the sealant layer 11 of the multilayer film 1 described above.

[0178] The other components included in the pinhole-resistant layer of the multilayer film for base materials may be one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0179] In the pinhole-resistant layer of the multilayer film for the base material, the ratio of the content of polyolefin resin to the total mass of the pinhole-resistant layer is preferably 50 to 100% by mass, more preferably 60 to 100% by mass, and may be, for example, 70 to 100% by mass and 85 to 100% by mass. The aforementioned ratio is typically 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 pinhole-resistant layer-forming composition for base materials described later.

[0180] The pinhole-resistant layer in the multilayer film for the base material may consist of one layer (single layer) or of two or more layers. When the pinhole-resistant layer consists of multiple layers, these layers may be identical or different, and the combination of these 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 multilayer film for the base material is preferably 2 to 50 μm. A thickness of the pinhole-resistant layer greater than or equal to the lower limit enhances its protective ability. A thickness of the pinhole-resistant layer less than or equal to the upper limit prevents the pinhole-resistant layer from becoming excessively thick. Here, "thickness of the pinhole-resistant layer" refers to the total thickness of the pinhole-resistant layer. For example, the thickness of a pinhole-resistant layer consisting of multiple layers refers to the total thickness of all the layers that make up the pinhole-resistant layer.

[0182] The ratio of the thickness of the pinhole-resistant layer to the thickness of the multilayer film for the base material is not particularly limited, but is preferably 5 to 40%. When the ratio is above the lower limit, the pinhole resistance of the multilayer film for the base material is further enhanced. When the ratio is below 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 bonding a multilayer film for the base material 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 constituent units derived from ethylene and constituent units derived from vinyl acetate, and may or may not have other constituent units. Examples of preferred ethylene-vinyl acetate copolymer resins include partially saponified ethylene-vinyl acetate copolymers.

[0185] The adhesive layer in the multilayer film for base material may contain only an adhesive (i.e., consist of an adhesive), or it may contain an adhesive and other components (which may be 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 multilayer film for base materials may contain only one type of adhesive, or two or more types. If there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0187] The other components included in the adhesive layer of the multilayer film for base material are not particularly limited and can be arbitrarily selected depending on the purpose, and may be, for example, resin components and non-resin components.

[0188] The other components in the adhesive layer of the multilayer film for base materials may consist of only one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0189] The ratio of the adhesive content in the adhesive layer of the multilayer film for the base material to the total mass of the adhesive layer may be, for example, 50 to 100% by mass. The aforementioned ratio is typically 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 adhesive layer forming composition for base materials described later.

[0190] The adhesive layer in the multilayer film for the base material may consist of one layer (single layer) or of two or more layers. When the adhesive layer consists of multiple layers, these layers may be identical or different, and the combination of these 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 multilayer film for the base material is preferably 2 to 40 μm. A thickness of the adhesive layer greater than or equal to the lower limit increases the adhesive strength between the two layers to be bonded. A thickness of the adhesive layer less than or equal to the upper limit prevents the adhesive layer from becoming excessively thick. Here, "thickness of the adhesive layer" refers to the total thickness of the adhesive layer. For example, the thickness of an adhesive layer consisting of multiple layers refers to the sum of the thicknesses of all the layers that make up the adhesive layer.

[0192] The ratio of the thickness of the adhesive layer to the thickness of the multilayer film for the base material is not particularly limited, but is preferably 5 to 40%. When the ratio is above the lower limit, the adhesive strength of the two layers to be bonded is increased. When the ratio is below the upper limit, the thickness of the adhesive layer is prevented from becoming excessive.

[0193] <First intermediate adhesive layer, second intermediate adhesive layer> The first and second intermediate adhesive layers each contain an adhesive. The adhesive is preferably an adhesive resin. Examples of the adhesive resin include polyolefin resins. The aforementioned polyolefin resin is a resin having structural units derived from olefins, 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). For polyolefin resins, random copolymers, graft copolymers, or block copolymers are preferable in terms of improved adhesion.

[0194] Examples of the ethylene copolymer include the ethylene copolymer described earlier as being included in the easy-peel layer, and its modified product (modified copolymer). Examples of the propylene copolymer include copolymers of propylene and vinyl group-containing monomers, and modified products thereof (modified copolymers). More specifically, examples of such propylene copolymers include maleic anhydride graft-modified linear low-density polypropylene and propylene-based thermoplastic elastomers. Examples of the butene-based copolymers include copolymers of 1-butene and vinyl group-containing monomers, copolymers of 2-butene and vinyl group-containing monomers, and modified products (modified copolymers) of these copolymers.

[0195] The first and second intermediate adhesive layers may consist solely of an adhesive (i.e., they may consist of an adhesive), or they may consist of an adhesive and other components (which may be referred to as "other components" in this specification) (i.e., they may consist of an adhesive and the other components).

[0196] The adhesives contained in the first and second intermediate adhesive layers may be of one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0197] The other components included in the first and second intermediate adhesive layers are not particularly limited and can be arbitrarily selected depending on the purpose, and may be, for example, resin components and non-resin components.

[0198] The other components contained in the first and second intermediate adhesive layers may consist of only one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0199] The ratio of the adhesive content in the first intermediate adhesive layer in the multilayer film for the base material to the total mass of the first intermediate adhesive layer may be, for example, 50 to 100% by mass. The aforementioned ratio is typically 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 first intermediate adhesive layer forming composition for the base material, which will be described later. The ratio of the adhesive content in the second intermediate adhesive layer in the multilayer film for the base material to the total mass of the second intermediate adhesive layer may be, for example, 50 to 100% by mass. The aforementioned ratio is typically 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 second intermediate adhesive layer forming composition for the base material, which will be described later.

[0200] The first intermediate adhesive layer and the second intermediate adhesive layer in the multilayer film for base material may each consist of one layer (single layer) or two or more layers. When the first intermediate adhesive layer or the second intermediate adhesive layer consists of multiple layers, these multiple layers may be the same or different from each other, and the combination of these multiple layers is not particularly limited as long as it does not impair the effects of the present invention.

[0201] In the multilayer film for the base material, the thickness of the first intermediate adhesive layer and the second intermediate adhesive layer are preferably 2 to 15 μm independently. When the thickness of the first and second intermediate adhesive layers is greater than or equal to the lower limit, the adhesive strength of the two layers to be bonded is increased. When the thickness of the first and second intermediate adhesive layers is less than or equal to the upper limit, it is prevented from becoming excessively thick. Here, "thickness of the first intermediate adhesive layer" refers to the total thickness of the first intermediate adhesive layer. For example, if the first intermediate adhesive layer consists of multiple layers, the thickness refers to the total thickness of all the layers that make up the first intermediate adhesive layer. 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 multilayer film for the base material is not particularly limited, but is preferably 3 to 20%. When the ratio is above the lower limit, the adhesive strength of the two layers to be bonded is increased. When the ratio is below the upper limit, the thickness of the first intermediate adhesive layer and the second intermediate adhesive layer is prevented from becoming excessive.

[0203] <Other layers> The multilayer film for the base material may include other layers that do not fall under any of the following categories, as long as they do not impair the effects of the present invention: the easy-peel layer, the first intermediate adhesive layer, the flexible layer, the second intermediate adhesive layer, the pinhole-resistant layer, and the adhesive layer.

[0204] The types and positions of the other layers in the multilayer film for the base material are not particularly limited and can be arbitrarily selected according to the purpose.

[0205] The other layers in the multilayer film for the base material may consist of only one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0206] In the multilayer film for the base material, the other layers may consist of one layer (single layer) or two or more layers. When the other layers consist of multiple layers, these layers may be identical or different, and the combination of these 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 multilayer film for the base material can be set arbitrarily according to their type and is not particularly limited.

[0208] If the multilayer film for the base material includes the aforementioned other layers, it may further include an intermediate adhesive layer for bonding the aforementioned other layers to the other layers. Examples of such intermediate adhesive layers include those similar to the first or second intermediate adhesive layer described above.

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

[0210] <<Manufacturing method for base material>> The aforementioned base material can be manufactured by known methods, depending on its type. For example, if the base material is a resin laminate comprising the foamed resin layer and the non-foamed resin layer described above, the base material can be manufactured by bonding one surface of the foamed resin layer to one surface of the non-foamed resin layer (or the adhesive layer within it if the non-foamed resin layer is the multilayer film for the base material) by heat lamination. This heat lamination may be carried out by, for example, a melt-pressure lamination method as described later in the examples, or by an extrusion lamination method. Among the non-foamed resin layers, the multilayer film for the base material can be manufactured in the same manner as the multilayer film (lid material) described above, except that, for example, the type of resin or resin composition used to form each layer is different.

[0211] Regardless of the manufacturing method, the resin composition that forms any of the layers in the multilayer film for the base material can be manufactured by adjusting the types and amounts of the constituent components so that the layer to be formed contains the desired components (constituent materials) in the desired amounts. For example, the ratio of the amounts of components that do not vaporize at room temperature in the resin composition is usually the same as the ratio of the amounts of those components in the layer formed from this resin composition.

[0212] Examples of resin compositions for forming an easy-peel layer in a multilayer film for base materials (which may be referred to herein as "composition for forming an easy-peel layer for base materials") include the polyolefin and, if necessary, the other components.

[0213] Examples of resin compositions for forming a flexible layer in a multilayer film for base materials (which may be referred to herein as "composition for forming a flexible layer for base materials") include a resin for the flexible layer and, if necessary, the other components mentioned above.

[0214] Examples of resin compositions for forming a pinhole-resistant layer in a multilayer film for base materials (which may be referred to herein as "composition for forming a pinhole-resistant layer for base materials") include the polyolefin and, if necessary, the other components.

[0215] Examples of resin compositions for forming an adhesive layer in a multilayer film for base materials (sometimes referred to herein as "composition for forming an adhesive layer for base materials"), a resin composition for forming a first intermediate adhesive layer (sometimes referred to herein as "composition for forming a first intermediate adhesive layer for base materials"), and a resin composition for forming a second intermediate adhesive layer (sometimes referred to herein as "composition for forming a second intermediate adhesive layer for base materials") include, for example, the adhesive and, if necessary, the other components.

[0216] <<Packaging>> Figure 2 is a schematic cross-sectional view showing an example of the packaging according to this embodiment. In Figure 2, components that are the same as those shown in previously explained figures are denoted by the same reference numerals as in those previously explained figures, and their detailed explanations are omitted. Note that in Figure 2, the distinction between each layer in the multilayer film 1 is omitted.

[0217] The packaging 10 shown here is composed of a multilayer film (lid material) 1 and a bottom material 8, as shown in Figure 1.

[0218] The packaging 10 is preferably a skin pack packaging. In this specification, "skin pack" refers to packaging in which the contents are placed on cardboard, corrugated cardboard, a bottom film, a tray, etc., a heated film is placed over it, and a vacuum is created in a chamber so that the film adheres tightly to the contents. The name "skin pack" comes from the characteristic that the film adheres to the product body as if it were skin, conforming to the shape of the product.

[0219] In the packaging 10, the multilayer film (lid material) 1 is constructed by laminating a sealant layer 11, a conforming layer 13, and a flexible layer 14 in the thickness direction. In the packaging 10, the ratio of the thickness of the flexible layer 14 to the thickness of the multilayer film (lid material) 1 is 2-30%. In the packaging 10, the tensile strength of the multilayer film (lid material) 1 at a temperature of 140°C is 0.2 N / mm². 2 More than 3.6N / mm 2 The following applies: In the packaging 10, under conditions of a temperature of 23°C and a relative humidity of 60%, the oxygen permeability of the multilayer film (lid material) 1 is 100 cc / (m²). 2 It is more than (day·atm). In the packaging 10, the dynamic modulus E' of the multilayer film (lid material) 1 at a temperature of 140°C is 1 × 10⁻⁶. 4 Pa or more 1×10 7 It is preferable that the value is Pa or less. In the package 10, during the thermomechanical analysis of the multilayer film (lid material) 1, it is preferable that the temperature at which a displacement of 2000 μm is shown is 120°C or higher. In the package 10, it is preferable that the gel fraction of the multilayer film (lid material) 1 is 30% or more. In the package 10, during the thermomechanical analysis of the multilayer film (lid material) 1, it is preferable that the displacement at a temperature of 100°C is 500 μm or less. In the package 10, it is preferable that the multilayer film (lid material) 1 is irradiated with an electron beam under the conditions of an absorbed dose of 13 to 300 kGy. In the package 10, it is preferable that the flexible layer 14 contains a polyethylene-based resin. In the package 10, it is preferable that the ratio of the thickness of the follow layer 13 to the thickness of the multilayer film (lid material) 1 is 10% or more. In the package 10, it is preferable that the ratio of the thickness of the sealant layer 11 to the thickness of the multilayer film (lid material) 1 is 5% or more. In the package 10, the tensile strength of the multilayer film (lid material) 1 at a temperature of 140°C is 0.2 N / mm 2 or more and 3 N / mm 2 or less.

[0220] In the package 10, the oxygen permeability of the bottom material 8 under the conditions of a temperature of 23°C and a relative humidity of 60% is preferably more than 100 cc / (m 2 ·day·atm).

[0221] By using the multilayer film 1 as the lid material, the package 10 retains the quality of the contained material, is excellent in followability to the contained material, and can follow the contained material softly.

[0222] One surface of the base material 8 (sometimes referred to as the "first surface" in this specification) 8a is a sealing surface, and a portion of the first surface 8a is in close contact with a portion of the first surface 11a of the sealant layer 11 in the multilayer film 1 by a seal. In Figure 2, the portion 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 sealing 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 contents 9 are sealed within this storage portion 10a.

[0223] If the base material 8 is the multilayer film for base materials, the first surface 8a of the base material 8 is the surface opposite to the flexible layer side of the easy-peel layer.

[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 bottom material 8 within the storage section 10a of the packaging body 10. However, these gaps may not exist in the packaging body 10 when the contents 9 are stored inside.

[0225] The packaging of this embodiment is not limited to those described above, and some components may be modified, deleted, or added without departing from the spirit of the present invention. In Figure 2, a packaging body 10 is shown that is constructed using the multilayer film 1 shown in Figure 1 as the lid material. However, the packaging body of this embodiment may be constructed using other multilayer films (lid materials).

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

[0227] The method for manufacturing the packaging of this embodiment includes the steps of: placing the contents on the base material; placing the lid material in an area on the base material that covers the contents and their surroundings; and heating the lid material to 90-250°C, bringing it into contact with the contents, molding it along the contents, and sealing the portion of the lid material that is in contact with the base material, thereby packaging the contents with the lid material and the base material. The test packaging described later can also be manufactured using the packaging manufacturing method of this embodiment.

[0228] In the step of placing the contents on the base material, for example, if a resin laminate equipped with the multilayer film for base material described above is used as the base material, the contents are placed on the easy-peel layer in the multilayer film for base material.

[0229] In the step of arranging the lid material, the multilayer film described earlier is arranged with the sealant layer facing the bottom material and the food side.

[0230] In the process of packaging the contents with the lid and base material by heating the lid material to 90-250°C, bringing it into contact with the contents, molding it along the contents, and bonding the portion of the lid material 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 above the lower limit, the seal strength is increased while maintaining easy-peel properties. When the heating temperature is below the upper limit, the package can be opened more easily.

[0232] The heating time for heating the lid material to 90-250°C can be adjusted as appropriate depending on the heating temperature, but is usually preferably 10-30 seconds. When the heating time is above the lower limit, the seal strength is increased while maintaining easy-peel properties. When the heating time is below the upper limit, the package can be opened more easily.

[0233] When the area where the contents are placed is evacuated, the pressure in this area 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, a package is obtained in which the lid material conforms more closely to the contents (seals better) and has better preservation properties.

[0234] The pressure applied when bonding (sealing) the portion of the lid material in contact with the bottom 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 below the upper limit, a package with good peelability can be obtained. [Examples]

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

[0236] [Example 1] <<Manufacturing of multilayer film (lid material)>> A multilayer film with the configuration shown in Figure 1 was manufactured using the following procedure. Specifically, ethylene-vinyl acetate copolymer (EVA, "V5714C" manufactured by Mitsui Dow Polychemicals) was prepared as the resin constituting the sealant layer. The resin used to make up the outer layer is low-density polyethylene (LDPE, density 0.922 g / cm³). 3, "F222NH" manufactured by Ube Maruzen Polyethylene Co., Ltd. was prepared. As the resin constituting the follow-up layers (the first follow-up layer and the second follow-up layer), sodium-based ionomer ("ION", "1601" manufactured by Mitsui Dow Polychemical Co., Ltd.) was prepared. As the resin constituting the flexible layer, metallocene linear low-density polyethylene (mLLDPE, "4040FC" manufactured by Ube Maruzen Polyethylene Co., Ltd.) was prepared. As the adhesive (adhesive resin) constituting the adhesive layers (the first adhesive layer and the second adhesive layer), maleic anhydride-modified polyethylene (modified PE, "NF536" manufactured by Mitsui Chemicals, Inc.) was prepared.

[0237] The temperature of the die was set at 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 24 μm), a follow-up layer (the first follow-up layer, thickness 29 μm), an adhesive layer (the first adhesive layer, thickness 8 μm), a flexible layer (thickness 10 μm), an adhesive layer (the second adhesive layer, thickness 8 μm), a follow-up layer (the second follow-up layer, thickness 17 μm), and an outer layer (thickness 24 μm) were laminated in this order in their thickness directions.

[0238] Next, the multilayer film obtained above was irradiated with an electron beam from the outside on the outer layer side under the conditions of an absorbed dose of 175 kGy and an acceleration voltage of 160 kV. Thus, the target multilayer film irradiated with an electron beam (hereinafter sometimes referred to as "lid material (I)") was obtained.

[0239] <<Evaluation of Multilayer Film (Lid Material)>> <Measurement of Tensile Strength at 140 °C> Regarding the electron beam-irradiated multilayer film (lid material (I)) obtained above, using a tensile strength measuring device ("AGS-X" manufactured by Shimadzu Corporation), in accordance with JIS K 7127:1999, the tensile strength was measured under the condition of a tensile speed of 500 mm / min. The results are shown in Table 1.

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

[0241] <Temperature indicating a displacement of 2000 μm; identification of the displacement at a temperature of 100°C> The electron beam-irradiated multilayer film (lid material (I)) obtained above was subjected to thermomechanical analysis in accordance with JIS K 7196 using a thermal analyzer (SII Corporation's "EXSTAR6000"). From the resulting thermomechanical analysis curve, the temperature (°C) at which a displacement of 2000 μm occurred and the displacement (μm) at a temperature of 100°C were determined. The results are shown in Table 1.

[0242] <Measurement of gel fraction> The gel fraction of the electron beam-irradiated multilayer film (lid material (I)) obtained above was measured in accordance with JIS K 6769. Specifically, a test piece measuring 3 cm x 3 cm (approximately 0.09 g) was cut from the multilayer film, wrapped in a 400-mesh stainless steel wire mesh (100 g), and immersed in xylene (18 mL) at 110 °C for 24 hours. Next, the test specimen, along with the wire mesh, was removed from the xylene solution and vacuum-dried at 110°C for 24 hours under a pressure of 1.7 kPa to obtain a dried sample of the immersed test specimen. The mass of the obtained dried sample was measured, and the gel fraction (%) of the electron-irradiated multilayer film was determined. The results are shown in Table 1.

[0243] <Measurement of oxygen permeability> The electron beam-irradiated multilayer film (lid material (I)) obtained above was subjected to oxygen permeability testing (cc / (m³)) in accordance with JIS K 7126-2:2006 under conditions of 23°C and 60% relative humidity.2 We measured (day and atm). The results are shown in Table 1.

[0244] <Evaluation of flexible layer breakage> The multilayer film (lid material (I)) obtained above, after electron beam irradiation, was visually inspected, and the presence or absence of layer breakage in the flexible layer was evaluated according to the following criteria. The results are shown in Table 1. [Evaluation Criteria] A: No tearing has occurred in the flexible layer. B: Some tearing has occurred in the flexible layer. C: A tear has occurred in the flexible layer.

[0245] <<Manufacturing of base material>> <Manufacturing of multilayer films for base materials> The multilayer film for the base material was manufactured using the following procedure. Specifically, 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 to constitute the easy-peel layer. The resin used to constitute the pinhole-resistant layer is metallocene-catalyzed linear low-density polyethylene (mLLDPE) (manufactured by Ube Maruzen Polyethylene Co., Ltd., "Yumerit® 1520F", density 0.913 g / cm³). 3 I prepared ). The resin used to make up the flexible layer is metallocene linear low-density polyethylene (mLLDPE, manufactured by Ube Maruzen Polyethylene Co., Ltd., "4040FC", density: 0.938 kg / m³). 3 I prepared a dose with an MFR of 3.5g / 10min. Acid-modified polypropylene (acid-modified PP, adhesive resin, "Admer QF551" manufactured by Mitsui Chemicals) was prepared as the resin constituting the first intermediate adhesive layer. Acid-modified polyethylene (acid-modified PE, adhesive resin, "Admer NF536" manufactured by Mitsui Chemicals) was prepared as the resin for the second intermediate adhesive layer. As the resin constituting the adhesive layer, we prepared an ethylene-vinyl acetate copolymer resin (EVA-based resin, adhesive resin, "Mersen® MX02D" manufactured by Tosoh Corporation).

[0246] A composition for forming an easy-peel layer for bottom materials was produced by mixing the aforementioned LDPE (70 parts by mass) and the aforementioned PP (30 parts by mass) at room temperature.

[0247] By setting the die temperature to 250°C and co-extruding the easy-peel layer forming composition for the base material, the acid-modified PP, the mLLDPE, the acid-modified PE, the mLLDPE, and the EVA resin in this order (co-extrusion T-die method), a multilayer film for the base material (thickness 70 μm) was produced, consisting 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 this order in the thickness direction.

[0248] <Manufacturing of base materials> A foamed resin sheet containing polystyrene resin (PSP) foam (manufactured by Chuo Kagaku Co., Ltd., 3000 μm thick) was used, and the exposed adhesive layer of the multilayer film for the base material obtained above was bonded to one side of the foamed resin sheet by heat lamination to obtain a base material (hereinafter sometimes referred to as "base material (α)"). The heat lamination of the foamed resin sheet and the multilayer film for the base material was performed by heat lamination using a roll device equipped with a melt-pressure roll. The melt-pressure roll was composed of a heating roll and a counter roll provided opposite to the heating roll, and the foamed resin sheet and the multilayer film for the base material were bonded together by melt-pressure bonding at 180°C between the heating roll and the counter roll.

[0249] <<Evaluation of the base material>> <Measurement of oxygen permeability> The oxygen permeability (cc / (m³)) of the bottom material obtained above was measured under conditions of 23°C and 60% relative humidity in accordance with JIS K 7126-2:2006 for the bottom material (bottom material (α)). 2 The daytime activity (atm) was measured. The results are shown in Table 5.

[0250] <<Manufacturing of packaging (test packaging)>> A 400g piece of chicken thigh meat was cut and used as the test meat. Then, using a continuous skin pack packaging machine (Multivac "T300"), the sealant layer in the lid material (I) and the easy-peel layer in the bottom material (α) were placed opposite each other, and the test meat was placed between the lid material (I) and the bottom material (α). While the area where the test meat was placed was evacuated, the periphery of the lid material (I) and bottom material (α) was heated and sealed under the conditions of a hot plate temperature (seal temperature) of 140°C and a sealing time of 10 seconds, thereby creating a test package (skin pack package). During the vacuuming process, the pressure in the area where the test meat was placed was set to 1000 Pa (10 mbar). A bottom material (α) measuring 20 cm x 20 cm was used. Multiple test packages were prepared using the same procedure. These test packages were frozen at -30°C in an air atmosphere and stored.

[0251] <<Evaluation of the packaging (test packaging)>> <Shape of contents> Three days after the start of storage, the samples were 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 inspected 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 being 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 samples were thawed from a frozen state of -30°C to 4°C over 16 hours. Immediately after thawing, the unopened test packages were visually inspected from the lid side, and the presence or absence of discoloration (surface oxidation discoloration) of the test meat was evaluated according to the following criteria. The results are shown in Table 6. [Evaluation Criteria] A: No discoloration has occurred in the test meat. B: The test meat has slightly discolored. C: Discoloration has occurred in the test meat.

[0253] <Drip> Three days after the start of storage, the samples were thawed from -30°C to 4°C over 16 hours. Immediately after thawing, the test meat was removed from the unopened test packaging and visually observed after 5 minutes. The amount of drip was evaluated according to the following criteria. The results are shown in Table 6. [Evaluation Criteria] A: No dripping has occurred. B: There is some dripping. C: Drip is occurring.

[0254] [Example 2] Except for changing the absorbed dose from 175 kGy to 120 kGy during electron beam irradiation of the multilayer film, an electron beam-irradiated multilayer film (hereinafter sometimes referred to as "lid material (II)") was manufactured and evaluated using the same method as in Example 1. Except for using the electron beam-irradiated multilayer film (lid material (II)), the packaging (test packaging) was manufactured and evaluated in the same manner as in Example 1. The results are shown in Tables 1, 5, and 6.

[0255] [Example 3] Except for changing the absorbed dose from 175 kGy to 90 kGy during electron beam irradiation of the multilayer film, an electron beam-irradiated multilayer film (hereinafter sometimes referred to as "lid material (III)") was manufactured and evaluated using the same method as in Example 1. Except for using the electron beam-irradiated multilayer film (lid material (III)), the packaging (test packaging) was manufactured and evaluated in the same manner as in Example 1. The results are shown in Tables 1, 5, and 6.

[0256] [Example 4] Except for changing the absorbed dose from 175 kGy to 15 kGy during electron beam irradiation of the multilayer film, an electron beam-irradiated multilayer film (hereinafter sometimes referred to as "lid material (IV)") was manufactured and evaluated using the same method as in Example 1. Except for using the electron beam-irradiated multilayer film (lid material (IV)), the packaging (test packaging) was manufactured and evaluated in the same manner as in Example 1. The results are shown in Tables 1, 5, and 6.

[0257] [Comparative Example 1] Except for not irradiating the multilayer film with an electron beam, a lid material (multilayer film without electron beam irradiation, hereinafter sometimes referred to as "lid material (V)") was manufactured and evaluated using the same method as in Example 1. Except for using a non-electron beam irradiated multilayer film (lid material (V)), the packaging (test packaging) was manufactured and evaluated using the same method as in Example 1. The results are shown in Tables 1, 5, and 8.

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

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

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

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

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

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

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

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

[0266] [Comparative Example 3] As the resin constituting the flexible layer, 6-nylon (Ny, Ube Industries, Ltd. "1030B2") is used instead of the aforementioned mLLDPE (Ube Maruzen Polyethylene Co., Ltd. "4040FC"), and the die temperature is set to 250°C. The EVA, the ION, the modified PE, the Ny, the modified PE, the ION, and the LDPE are co-extruded in this order (co-extrusion T-die method) to produce a sealant layer (thickness 24 μm) and a follow-up layer (first follow-up 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 laminating the following layers in this order in the thickness direction: a 9 μm layer, 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 conforming layer (second conforming layer, thickness 17 μm), and an outer layer (thickness 25 μm). Except for using the electron beam-irradiated multilayer film (lid material (XIV)), the packaging (test packaging) was manufactured and evaluated in the same manner as in Example 1. The results are shown in Tables 3, 5, and 8.

[0267] [Example 12] As the resin constituting the flexible layer, 6-nylon (Ny, Ube Industries, Ltd. "1030B2") is used instead of the aforementioned mLLDPE (Ube Maruzen Polyethylene Co., Ltd. "4040FC"), the die temperature is set to 250°C, and the EVA, the ION, the modified PE, the Ny, the modified PE, the ION, and the LDPE are co-extruded in this order (co-extrusion T-die method) to produce a sealant layer (thickness 29 μm), a follow-up layer (first follow-up layer, thickness 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 following order in the thickness direction: a 29 μm layer, 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 conforming layer (second conforming layer, thickness 17 μm), and an outer layer (thickness 24 μm). Except for using the electron beam-irradiated multilayer film (lid material (XV)), the packaging (test packaging) was manufactured and evaluated using the same method as in Example 1. The results are shown in Tables 3, 5, and 7.

[0268] [Comparative Example 4] As the resin constituting the flexible layer, 6-nylon (Ny, manufactured by Ube Maruzen Polyethylene Co., Ltd., "1030B2") is used instead of the aforementioned mLLDPE (manufactured by Ube Maruzen Polyethylene Co., Ltd., "4040FC"), and as the resin constituting the second adhesive layer, ethylene-vinyl alcohol copolymer (EVOH, manufactured by Kuraray Co., Ltd., "J171B") is used instead of the aforementioned modified PE (manufactured by Mitsui Chemicals, Inc., "NF536"), and 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 lid material (electron beam irradiated multilayer film, hereinafter sometimes referred to as "lid material (XVI)") was manufactured and evaluated in the same manner as in Example 1, except that a multilayer film (thickness 120 μm) was manufactured by laminating a sealant layer (thickness 24 μm), a follow-up layer (first follow-up layer, thickness 40 μm), an adhesive layer (first adhesive layer, thickness 8 μm), a flexible layer (thickness 24 μm), an adhesive layer (second adhesive layer, thickness 6 μm), a follow-up layer (second follow-up layer, thickness 10 μm), and an outer layer (thickness 8 μm) in this order in the thickness direction using the co-extrusion T-die method. Except for using the electron beam-irradiated multilayer film (lid material (XVI)), the packaging (test packaging) was manufactured 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, instead of the aforementioned LDPE (F222NH manufactured by Ube Maruzen Polyethylene Co., Ltd.), linear low-density polyethylene (LLDPE, density 0.938 g / cm³) is used. 3 Except for using "4040FC" manufactured by Ube Maruzen Polyethylene Co., Ltd., the lid material (electron beam irradiated multilayer film, hereinafter sometimes referred to as "lid material (XVII)") was manufactured and evaluated using the same method as in Example 1. Except for using the electron beam-irradiated multilayer film (lid material (XVII)), the packaging (test packaging) was manufactured and evaluated in the same manner as in Example 1. The results are shown in Tables 4, 5, and 7.

[0270] [Example 14] As the resin constituting the outer layer, instead of the aforementioned LDPE (F222NH manufactured by Ube Maruzen Polyethylene Co., Ltd.), high-density polyethylene (HDPE, density 0.949 g / cm³) is used. 3 Except for using Prime Polymer's "3300F", the lid material (electron beam irradiated multilayer film, hereinafter sometimes referred to as "lid material (XVIII)") was manufactured and evaluated in the same manner as in Example 1. Except for using the electron beam-irradiated multilayer film (lid material (XVIII)), the packaging (test packaging) was manufactured and evaluated in the same manner as in Example 1. The results are shown in Tables 4, 5, and 7.

[0271] [Example 15] Except for using ethylene-vinyl acetate copolymer (EVA, Mitsui Dow Polychemicals "V5714C") instead of the aforementioned LDPE (Ube Maruzen Polyethylene Co., Ltd. "F222NH") ​​as the resin constituting the outer layer, a lid material (electron beam irradiated multilayer film, hereinafter sometimes referred to as "lid material (XIX)") was manufactured and evaluated using the same method as in Example 1. Except for using the electron beam-irradiated multilayer film (lid material (XIX)), the packaging (test packaging) was manufactured and evaluated in the same manner as in Example 1. The results are shown in Tables 4, 5, and 8.

[0272] [Example 16] Except for not providing an outer layer and setting the thickness of the second follow-up layer to 41 μm, a lid material (a multilayer film irradiated with an electron beam, hereinafter sometimes referred to as "lid material (XX)") was manufactured and evaluated using the same method as in Example 1. Except for using the electron beam-irradiated multilayer film (lid material (XX)), the packaging (test packaging) was manufactured and evaluated in the same manner as in Example 1. The results are shown in Tables 4, 5, and 8.

[0273] [Example 17] Except for not providing a first follow-up layer and setting the sealant layer thickness to 53 μm, a lid material (electron beam irradiated multilayer film, hereinafter sometimes referred to as "lid material (XXI)") was manufactured and evaluated using the same method as in Example 1. Except for using the electron beam-irradiated multilayer film (lid material (XXI)), the packaging (test packaging) was manufactured and evaluated in the same manner as in Example 1. 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 Examples 1 to 17, the lid material of the test packaging had a ratio of the thickness of the flexible layer to the thickness of the multilayer film of 2% or more, and therefore, no tearing of the flexible layer occurred in any of them.

[0283] The test packaging materials of Examples 1 to 17 had a tensile strength of 3.6 N / mm² at 140°C. 2 As a result, although the shape of the packaged test meat in Example 7 was slightly crushed, the test packages in Examples 1-6 and 8-17 were all able to maintain the shape of the packaged test meat. The test packaging materials in Examples 1 to 17 had an oxygen permeability of 100 cc / (m³). 2 Because the temperature was above (day·atm), no discoloration occurred in any of the packaged test meats. The test packaging materials in Examples 1 to 17 had a tensile strength of 0.2 N / mm² at 140°C. 2 Therefore, although some drip occurred in the test meat removed from the test packaging in Example 11, no drip occurred in the test packaging in Examples 1-10 and 12-17.

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

[0285] In contrast, the test packaging of Comparative Example 1, which was not subjected to electron beam irradiation of the multilayer film, had a tensile strength of 0.2 N / mm² at 140°C. 2 Because the pressure was below a certain level, the lid material's ability to conform to the test meat decreased, and the removed test meat had developed drip.

[0286] In Comparative Example 2, the ratio of the thickness of the flexible layer to the thickness of the multilayer film was less than 2%, resulting in tearing of the flexible layer and a problem with the quality of the lid material. Therefore, the production and evaluation of lid materials from Comparative Example 2 (test lids) were not carried out.

[0287] In Comparative Example 3, the test packaging used Ny as the resin constituting the flexible layer, resulting in a multilayer film with an oxygen permeability of 100 cc / (m²). 2 Because the temperature fell below (day·atm), discoloration occurred in the packaged test meat.

[0288] In the test packaging of Comparative Example 4, Ny was used as the resin constituting the flexible layer, resulting in an oxygen permeability of 100 cc / (m³). 2 Because the temperature fell below (day·atm), discoloration occurred in the packaged test meat. In addition, in Comparative Example 4, the test package used EVOH as the resin constituting the second adhesive layer, resulting in a tensile strength of 3.6 N / mm at 140°C. 2 Because it was too hot, the packaged test meat was crushed. [Industrial applicability]

[0289] The present invention provides a multilayer film that maintains the quality of its contents and exhibits excellent conformability to the contents, as well as a packaging material (e.g., a skin pack packaging material) using the same. [Explanation of Symbols]

[0290] 1. Multilayer film (lid 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. It is a multilayer film, The aforementioned multilayer film is constructed by laminating a sealant layer, a conforming layer containing an ionomer, and a flexible layer containing a polyethylene resin in the thickness direction. 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, was 1.6 N / mm². ２ 3.6N / mm or more ２ The following: The oxygen permeability of the multilayer film, measured in accordance with JIS K 7126-2:2006 under conditions of 23°C and 60% relative humidity, was 100 cc / (m²). ２ (day ATM) is above, A multilayer film obtained by irradiating the aforementioned multilayer film with an electron beam under conditions of an absorbed dose of 120 to 300 kGy.

2. The dynamic modulus E' of the multilayer film at a temperature of 140°C, measured in accordance with JIS K 7244-4, is 1 × 10⁻⁶ ４ Pa or more 1×10 ７ A multilayer film according to claim 1, wherein the hardness is Pa or less.

3. The multilayer film according to claim 1 or 2, wherein the temperature at which a displacement of 2000 μm is observed during thermomechanical analysis of the multilayer film, 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 gel fraction of the multilayer film, as measured in accordance with JIS K 6769, is 30% or more.

5. The multilayer film according to claim 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 claims 1 to 5, wherein the ratio of the thickness of the follow-up layer to the thickness of the multilayer film is 10% or more.

7. The multilayer film according to any one of claims 1 to 6, wherein the ratio of the thickness of the sealant layer to the thickness of the multilayer film is 5% or more.

8. The tensile strength of the multilayer film at a temperature of 140°C, measured in accordance with JIS K 7127:1999, was 1.6 N / mm². ２ 3N / mm or more ２ The multilayer film according to any one of claims 1 to 7, which is as follows:

9. A packaging body comprising a multilayer film according to any one of claims 1 to 8.

10. The packaging body according to claim 9, wherein the packaging body is a skin pack packaging body.

11. A method for manufacturing a package in which contents are packaged by a lid material and a bottom material, comprising the steps of: placing the contents on the bottom material; placing the lid material in a region on the bottom material that covers the contents and their surroundings; and molding the lid material along the contents while vacuuming, and bringing it into contact with the contents while heating it to 90 to 250°C, and bonding the portion of the lid material in contact with the bottom material to the bottom material, thereby packaging the contents with the lid material and the bottom material, wherein the lid material is made of a multilayer film as described in any one of claims 1 to 8.

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