Biaxially stretched polyethylene film, laminate film, and package

Abstract

[Problem] To provide a biaxially stretched polyethylene film wherein a film that uses a polyethylene-based resin as a main starting material can be stably stretched in two axial directions at the time of stretching; a laminate film; and a package. [Solution] Provided is a biaxially stretched polyethylene film 10 which comprises a base material layer 20 and a surface layer A, wherein the relationship between the calculated MFR (MFRc) of the base material layer 20 and the calculated MFR (MFRs1) of the surface layer A satisfies 0.3 < MFRc / MFRs1 < 1.9. Also provided is a biaxially stretched polyethylene film 10A which comprises at least a base material layer, a surface layer A, and a surface layer B, wherein the relationship between the calculated MFR (MFRc) of the base material layer 20 and the calculated MFR (MFRs1) of the surface layer A satisfies 0.3 < MFRc / MFRs1 < 1.9, and the relationship between the calculated MFR (MFRc) of the base material layer 20 and the calculated MFR (MFRs2) of the surface layer B satisfies 0.3 < MFRc / MFRs2 < 1.9.

Description

Biaxially oriented polyethylene film, laminate film, and packaging

[0001] The present invention relates to a biaxially oriented polyethylene film that is oriented in both the machine direction (MD) and the transverse direction (TD), a laminate film using this polyethylene film, and a package using this laminate film.

[0002] Generally, packaging materials for packaging products such as food and daily necessities use films that are laminated with multiple resin films made of different types of resin materials. This type of laminated film achieves good quality and performance as a film product by laminating films with various functions. In recent years, growing awareness of environmental issues has led to a demand for recycling in the field of this type of resin film.

[0003] However, in the case of films in which multiple types of resins are laminated, even if the resins that make up the film are remelted during recycling, a mixture of incompatible resins results, significantly reducing the quality of the recycled resource and making it unsuitable as a recycled material. Therefore, films in which the multiple laminated films are made of a single material (monomaterial) have been proposed.

[0004] In single-material laminate films, polypropylene-based resins are generally used to obtain properties such as rigidity and heat resistance, but in recent years, polyethylene-based laminate films have been attracting attention as single-material laminate films. Known examples of polyethylene-based laminate films include a polyethylene-based sealant film with excellent heat-sealing suitability and a polyethylene-based laminate film having a base film made of a stretched film made of the same polyethylene material as the sealant film (see Patent Document 1).

[0005] However, conventional polyethylene-based laminate films as described above tend to be more flexible and have a lower melting point than laminate films made of polypropylene-based resins, and therefore may not achieve the film properties required for packaging, etc. Therefore, methods for achieving the film properties required for packaging, etc. in polyethylene-based laminate films include using high-density resin materials as the film's constituent materials to increase rigidity, or modifying the film by resin blending. However, such polyethylene-based laminate films often fail to exhibit good stretchability, for example, when stretched in biaxial directions, i.e., the machine direction (MD) and the transverse direction (TD), the films may break, making it impossible to form them into a film. Therefore, it is desirable to enable stable film production even in films made from a single material primarily composed of polyethylene-based resins.

[0006] Japanese Patent Application Laid-Open No. 2019-189333

[0007] The present invention has been made in consideration of the above points, and provides a biaxially oriented polyethylene film, a laminate film, and a packaging material, which are films made primarily from polyethylene resin and can be stably stretched in two axial directions during stretching.

[0008] That is, the first invention relates to a biaxially oriented film comprising a base layer and a surface layer A arranged on one side of the base layer, and stretched in two axial directions, that is, the machine direction (MD) and the transverse direction (TD), wherein the base layer is mainly composed of a polyethylene-based resin, and the relationship between the calculated MFR (MFRc) of the base layer and the calculated MFR (MFRs1) of the surface layer A satisfies 0.3 < MFRc / MFRs1 < 1.9.

[0009] A second invention relates to a biaxially oriented film comprising at least three layers, including a base layer, a surface layer A arranged on one side of the base layer, and a surface layer B arranged on the other side of the base layer, and stretched in two axial directions, that is, the machine direction (MD) and the transverse direction (TD), wherein the base layer is mainly composed of a polyethylene resin, the relationship between the calculated MFR (MFRc) of the base layer and the calculated MFR (MFRs1) of the surface layer A satisfies 0.3 < MFRc / MFRs1 < 1.9, and the relationship between the calculated MFR (MFRc) of the base layer and the calculated MFR (MFRs2) of the surface layer B satisfies 0.3 < MFRc / MFRs2 < 1.9.

[0010] A third invention relates to the biaxially oriented polyethylene film of the first invention, wherein an inorganic vapor deposition layer is disposed on the surface layer A side.

[0011] A fourth invention relates to the biaxially oriented polyethylene film of the second invention, wherein at least one of the surface layer A and the surface layer B has an inorganic vapor deposition layer.

[0012] A fifth invention relates to the biaxially oriented polyethylene film according to the first invention, wherein the surface layer A is mainly made of a polyethylene-based resin.

[0013] A sixth aspect of the present invention relates to the biaxially oriented polyethylene film according to the second aspect of the present invention, wherein the surface layer A and / or the surface layer B is / are mainly made of a polyethylene-based resin.

[0014] The seventh invention relates to a laminate film characterized in that a sealant film made of at least a polyethylene resin is laminated on the biaxially oriented polyethylene film according to the first or second invention.

[0015] The eighth invention relates to a laminate film characterized in that a sealant film made of at least a polyethylene resin is laminated on the biaxially oriented polyethylene film according to the third or fourth invention.

[0016] A ninth aspect of the present invention relates to a package comprising the laminate film according to the seventh aspect of the present invention.

[0017] A tenth aspect of the present invention relates to a package comprising the laminate film according to the eighth aspect of the present invention.

[0018] The biaxially oriented polyethylene film according to the first aspect of the present invention is a biaxially oriented film comprising a base layer and a surface layer A disposed on one side of the base layer, and stretched in two axial directions, i.e., the longitudinal (MD) direction and the transverse (TD) direction, wherein the base layer is mainly composed of a polyethylene-based resin, and the calculated MFR (MFRc) of the base layer and the calculated MFR (MFRs1) of the surface layer A satisfy the relationship 0.3 < MFRc / MFRs1 < 1.9. Therefore, the occurrence of breakage due to uneven stretching during stretching is suppressed, enabling stable stretching processing, and a film with good film-forming suitability can be provided.

[0019] According to a second aspect of the present invention, there is provided a biaxially oriented polyethylene film comprising at least three layers, including a base layer, a surface layer A disposed on one side of the base layer, and a surface layer B disposed on the other side of the base layer, and the biaxially oriented film is stretched in two axial directions, i.e., the longitudinal (MD) direction and the transverse (TD) direction. The base layer is mainly composed of a polyethylene-based resin, and the relationship between the calculated MFR (MFRc) of the base layer and the calculated MFR (MFRs1) of the surface layer A satisfies 0.3 < MFRc / MFRs1 < 1.9, and the relationship between the calculated MFR (MFRc) of the base layer and the calculated MFR (MFRs2) of the surface layer B satisfies 0.3 < MFRc / MFRs2 < 1.9. Therefore, the occurrence of breakage due to uneven stretching during stretching is suppressed, enabling stable stretching treatment, and a film with good film-forming suitability can be provided.

[0020] According to the biaxially oriented polyethylene film of the third invention, since an inorganic vapor deposition layer is disposed on the surface layer A side in the first invention, the biaxially oriented polyethylene film can be endowed with gas barrier properties.

[0021] According to the biaxially oriented polyethylene film of the fourth invention, in the second invention, an inorganic vapor deposition layer is disposed on at least one of the surface layer A and the surface layer B, so that the biaxially oriented polyethylene film can be imparted with gas barrier properties.

[0022] According to the biaxially oriented polyethylene film of the fifth invention, in the first invention, the surface layer A is mainly made of a polyethylene-based resin, which makes it easier to realize a film made of a single material.

[0023] According to the biaxially oriented polyethylene film of the sixth invention, in the second invention, the surface layer A and / or the surface layer B are mainly made of a polyethylene-based resin, making it easier to realize a film made of a single material.

[0024] The laminate film of the seventh invention is formed by laminating a sealant film made of at least a polyethylene-based resin onto the biaxially oriented polyethylene film described in the first or second invention, and is therefore a promising alternative to existing laminate films.

[0025] The laminate film of the eighth invention is formed by laminating a sealant film made of at least a polyethylene-based resin onto the biaxially oriented polyethylene film described in the third or fourth invention, and is therefore a promising alternative to existing laminate films.

[0026] The packaging body according to the ninth aspect of the present invention is made of the laminate film according to the seventh aspect of the present invention, and is therefore a promising alternative to existing packaging bodies.

[0027] The packaging body according to the tenth aspect of the present invention is made of the laminate film according to the eighth aspect of the present invention, and is therefore a promising alternative to existing packaging bodies.

[0028] 1 is a schematic cross-sectional view of a biaxially oriented polyethylene film according to one embodiment of the present invention; FIG. 2 is a schematic cross-sectional view of a biaxially oriented polyethylene film according to another embodiment; FIG. 3 is a schematic cross-sectional view of a laminate film using the biaxially oriented polyethylene film of FIG.

[0029] The biaxially oriented polyethylene film 10 according to one embodiment of the present invention shown in Figure 1 is a laminated film comprising a base layer 20 and a surface layer A disposed on one side of the base layer 20, and stretched in two axial directions, the machine direction (MD) and the transverse direction (TD). The biaxially oriented polyethylene film 10 of the present invention can be used as a base film for a laminate film to which vapor deposition or the like is applied. This laminate film can be suitably used for various packages (packaging bags) for, for example, food, cosmetics, pharmaceuticals, daily necessities, parts, and other products.

[0030] The biaxially oriented polyethylene film of the present invention is made of a single material (monomaterial) consisting of a polyethylene resin. The term "monomaterial" as used herein means that the entire film is made primarily of the same type of resin material. For example, the film may contain at least about 80%, preferably at least about 90%, of the main material. Because the film is made of a single material, it can be used effectively as a recycled material.

[0031] The biaxially oriented polyethylene film of the present invention is a laminated film made primarily of a polyethylene resin. The polyethylene resin used is appropriately selected from polyethylene resins derived from petroleum, biomass, recycled materials, chemically recycled materials, etc., and is an ethylene homopolymer or a random copolymer of ethylene and an α-olefin having 3 or more carbon atoms, such as propylene, 1-butene, 1-heptene, 1-hexene, or 1-octene. The polyethylene resin may also be a mixture of one or more of the above.

[0032] The resin raw material for the biaxially oriented polyethylene film of the present invention may be appropriately blended with other olefin resins, olefin elastomers such as α-olefin copolymers, etc., within the scope of not impairing the object of the present invention. Similarly, additives such as antioxidants, neutralizing agents, antistatic agents, antifogging agents, lubricants, nucleating agents, colorants, and antiblocking agents may also be appropriately blended.

[0033] The substrate layer 20 is formed to be relatively thicker than the other layers. This substrate layer 20 is mainly composed of a polyethylene-based resin, but any suitable resin material can be used as the constituent material as long as the conditions for single-material construction are met. The substrate layer 20 may contain additives such as surfactants as needed. For example, the addition of a surfactant can improve the slip properties and anti-blocking properties of the biaxially oriented polyethylene film 10.

[0034] Furthermore, in the substrate layer 20, if necessary, a surface treatment may be applied to the substrate layer surface opposite the surface layer A described below to increase the surface wet tension, thereby imparting printability and lamination suitability. The wet tension is preferably 36 mN / m or more; if the wet tension is too low, it is undesirable because it may cause poor printing or lamination. The wet tension is measured by a wet tension test method in accordance with JIS K 6768 (1999). Examples of surface treatments include known surface treatment methods such as atmospheric pressure plasma treatment, flame treatment, and corona discharge treatment.

[0035] The surface layer A corresponds to one surface layer of the biaxially oriented polyethylene film 10, and can be used as the processed surface when surface treatment such as vapor deposition is performed on the film surface. The surface layer A can be made of any suitable resin material that can be used on the film surface as long as the conditions for single-material construction are met, but it is preferable to use a polyethylene-based resin as the main component. If the surface layer A is made primarily of a polyethylene-based resin, the proportion of polyethylene-based resin in the entire film will be higher, making it easier to realize a single-material film. An anti-blocking agent or the like may be added to the surface layer A as needed.

[0036] Furthermore, if necessary, the surface layer A may be subjected to a surface treatment to increase the wet tension of the surface layer, thereby imparting suitability for vapor deposition, printing, and lamination. The wet tension is preferably 36 mN / m or more; if the wet tension is too low, it is undesirable because it may cause poor printing or poor lamination. The wet tension is measured by a wet tension test method in accordance with JIS K 6768 (1999). Examples of surface treatments include known surface treatment methods such as atmospheric pressure plasma treatment, flame treatment, and corona discharge treatment.

[0037] The biaxially oriented polyethylene film 10 of the present invention can be obtained by a known film forming method such as the T-die method or the inflation method. In particular, it is preferable to form a sheet shaped by the T-die method by stretching it. Film forming by the T-die method is advantageous in that it can achieve the high thickness precision required for base films for printing and laminating films.

[0038] The biaxially oriented polyethylene film 10 is a biaxially oriented film stretched in both the machine direction (MD) and the transverse direction (TD). Biaxial stretching can be performed in either sequential or simultaneous biaxial stretching. The production of biaxially oriented films results in resin orientation in both the machine direction (MD) and the transverse direction (TD), which allows for improvements in thickness accuracy (e.g., thinning) and mechanical properties such as strength, and is also suitable for mass production. The stretching ratio is approximately 2 to 8 times in the machine direction (MD) and 4 to 12 times in the transverse direction (TD).

[0039] The thickness of the biaxially oriented polyethylene film 10 of the present invention is not particularly limited and can be appropriately determined depending on the demand and application, for example, 5 to 100 μm, preferably 10 to 70 μm. The thickness of the base layer 20 is 4 to 99 μm, preferably approximately 9 to 69 μm. The thickness of the surface layer A is 0.3 to 5.0 μm, preferably approximately 0.5 to 3.0 μm. If the surface layer A is too thin, there is a risk of poor appearance due to uneven film thickness, and if an antiblocking agent is added to the surface layer A, there is a risk of the antiblocking agent falling off. If the surface layer A is too thick, there is a risk of the surface layer A not being able to be made of a single material, and therefore functionality cannot be imparted to the surface layer A. If an antiblocking agent is added to the surface layer A, the relative increase in the amount of the antiblocking agent present may reduce the sense of transparency.

[0040] In the biaxially oriented polyethylene film 10 of the present invention, an inorganic vapor deposition layer 30 is preferably disposed on the surface layer A side. The inorganic vapor deposition layer 30 is a layer that prevents the permeation of gases such as water vapor and oxygen. When provided on the surface layer A, it can impart gas barrier properties to the biaxially oriented polyethylene film 10. This inorganic vapor deposition layer 30 is formed on the surface layer A directly or via an anchor coat layer by a known vapor deposition method such as vacuum deposition, sputtering, or ion plating. Examples of materials that constitute the inorganic vapor deposition layer 30 include known metals such as aluminum, gold, silver, copper, and chromium, as well as inorganic materials such as oxides of these metals, other inorganic oxides, sulfides, and nitrides. The inorganic vapor deposition layer 30 can be a single thin film layer made of any of these inorganic materials, or a composite layer or multiple layers made of one or more types of inorganic materials.

[0041] Conventional laminate films primarily made from polyethylene resins have sometimes failed to form into films when stretched biaxially in the machine direction (MD) and transverse direction (TD) during film formation due to breakage. The inventors have therefore conducted extensive research and found that the relationship between the melt flow rate (MFR) of the base layer material and the MFR of the surface layer material affects the film-forming suitability of the laminate film. They have thus derived a relationship between the base layer and the surface layer that results in good film-forming suitability for laminate films primarily made from polyethylene resins. Specifically, the biaxially stretched polyethylene film 10 of the present invention is characterized in that the calculated MFR (MFRc) of the base layer 20 and the calculated MFR (MFRs1) of the surface layer A satisfy the relationship 0.3<MFRc / MFRs1<1.9.

[0042] The calculated MFR (MFRc) of the base layer 20 is the MFR of one or more types of resin materials constituting the base layer 20, and is calculated from the MFR and blending ratio of each resin material. Similarly, the calculated MFR (MFRs1) of the surface layer A is the MFR of one or more types of resin materials constituting the surface layer A. The MFR of each resin material is a value measured in accordance with JIS K 7210 (2014) under conditions of 190°C and 2.16 kg.

[0043] MFRc / MFRs1 is an index that represents the relationship between the fluidity of the resin material constituting the base layer 20 and the resin material constituting the surface layer A, and can be used as one index that represents the stretchability of a film. According to this index, when the MFRc / MFRs1 value is 1.0, the fluidity of the resin material of the base layer 20 and the surface layer A can be considered to be approximately equal. Furthermore, a smaller MFRc / MFRs1 value represents a state in which the fluidity of the resin of the base layer 20 is lower than that of the resin of the surface layer A, and a larger MFRc / MFRs1 value represents a state in which the fluidity of the resin of the base layer 20 is higher than that of the resin of the surface layer A. If the MFRc / MFRs1 value is too small, uneven stretching in the transverse (TD) direction is more likely to occur during stretching in the TD direction, which may result in breakage. On the other hand, if the value of MFRc / MFRs1 is too large, uneven stretching in the machine direction (MD) is likely to occur during stretching in the machine direction (MD), and there is a risk of breakage during stretching in the transverse direction (TD).

[0044] For this reason, in a laminate film made primarily from a polyethylene resin, if the fluidity (calculated MFR) of the base layer 20 and the surface layer A differs significantly, uneven stretching that causes breakage during stretching in the machine direction (MD) or transverse direction (TD) is likely to occur, and good film-forming suitability may not be obtained. It is preferable that the fluidity (calculated MFR) of the base layer 20 and the surface layer A is close to each other, and even if they differ, as long as they are within a certain range, i.e., satisfy the relationship 0.3<MFRc / MFRs1<1.9, breakage due to uneven stretching during stretching is suppressed, allowing for stable stretching processing and good film-forming suitability.

[0045] Figure 2 shows a biaxially oriented polyethylene film 10A according to another embodiment of the present invention, which comprises at least three layers including a base layer 20, a surface layer A disposed on one side of the base layer 20, and a surface layer B disposed on the other side of the base layer 20, and is stretched in two axial directions, i.e., the machine direction (MD) and the transverse direction (TD). The biaxially oriented polyethylene film 10A of the present invention can be suitably used as a base film for a laminate film to be subjected to vapor deposition or the like, similar to the biaxially oriented polyethylene film 10. In Figure 2, the same reference numerals as those in Figure 1 represent the same components, and their explanation will be omitted.

[0046] Surface layer B is the surface layer opposite surface layer A, and can be used as the processed surface when surface processing such as vapor deposition is performed on the film surface. Therefore, both sides of biaxially oriented polyethylene film 10A can be processed, enhancing convenience. Like surface layer A, surface layer B can be made of any suitable resin material that can be used on film surfaces as long as the conditions for single-material construction are met. From the perspective of single-material construction of the film, it is preferable to use a polyethylene-based resin as the main component. Surface layer B may contain an antiblocking agent or the like, as needed. Furthermore, the thickness of surface layer B is approximately 0.3 to 5.0 μm, preferably 0.5 to 3.0 μm. Surface layers A and B may be made of the same resin or different resins.

[0047] Furthermore, similar to the surface layer A, the surface layer B may be subjected to a surface treatment as needed to increase the wet tension of the surface layer, thereby imparting suitability for vapor deposition, printing, and lamination. The wet tension is preferably 36 mN / m or more; if the wet tension is too low, it is not preferable because it may cause poor printing or lamination. The wet tension is measured by a wet tension test method in accordance with JIS K 6768 (1999). Examples of surface treatments include known surface treatment methods such as atmospheric pressure plasma treatment, flame treatment, and corona discharge treatment.

[0048] In the biaxially oriented polyethylene film 10A, it is preferable that an inorganic vapor deposition layer 30 is disposed on at least one of the surface layer A side and the surface layer B side. In the example shown in the figure, the inorganic vapor deposition layer 30 is disposed on the surface layer B side. By disposing the inorganic vapor deposition layer 30 on at least one surface of the biaxially oriented polyethylene film 10A, gas barrier properties can be imparted to the biaxially oriented polyethylene film 10A. Although not shown, the inorganic vapor deposition layer 30 may be disposed on the surface layer A side instead of the surface layer B side, or may be disposed on both the surface layers A and B.

[0049] The biaxially oriented polyethylene film 10A is characterized in that the relationship between the base layer and the surface layer that provides good film-forming suitability is such that the relationship between the calculated MFR (MFRc) of the base layer 20 and the calculated MFR (MFRs1) of the surface layer A satisfies 0.3 < MFRc / MFRs1 < 1.9, and the relationship between the calculated MFR (MFRc) of the base layer 20 and the calculated MFR (MFRs2) of the surface layer B satisfies 0.3 < MFRc / MFRs2 < 1.9.

[0050] As described above, MFRc / MFRs1 represents the relationship between the fluidity of the resin material constituting the base layer 20 and the resin material constituting the surface layer A, and can be used as one index for expressing the stretchability of a film. An MFRc / MFRs1 value of 1.0 can be considered to indicate that the fluidity of the resin material of the base layer 20 and the surface layer A is approximately equal. If the MFRc / MFRs1 value is too small, the fluidity of the resin of the base layer 20 will be too low compared to the fluidity of the resin of the surface layer A, which may result in uneven stretching in the transverse (TD) direction during stretching in the transverse (TD) direction, leading to the risk of breakage. On the other hand, if the MFRc / MFRs1 value is too large, the fluidity of the resin of the base layer 20 will be too high compared to the fluidity of the resin of the surface layer A, which may result in uneven stretching in the longitudinal (MD) direction during stretching in the longitudinal (MD) direction, leading to the risk of breakage. It is preferable that the fluidity (calculated MFR) of the base layer 20 and the surface layer A is close to each other. Even if they are different, as long as they are within a certain range, i.e., the relationship 0.3<MFRc / MFRs1<1.9 is satisfied, the occurrence of breakage due to uneven stretching during stretching is suppressed, allowing for stable stretching processing and improving suitability for film formation.

[0051] The calculated MFR (MFRs2) of the surface layer B is the MFR of one or more resin materials constituting the surface layer B. MFRc / MFRs2 is an index that represents the relationship between the fluidity of the resin material constituting the base layer 20 and the resin material constituting the surface layer B, and can be used as one index representing the stretchability of a film. As with MFRc / MFRs1, a smaller value of MFRc / MFRs2 indicates a state in which the fluidity of the resin of the base layer 20 is lower than that of the resin of the surface layer B, and a larger value indicates a state in which the fluidity of the resin of the base layer 20 is higher than that of the resin of the surface layer B. If the value of MFRc / MFRs2 is too small, uneven stretching in the transverse (TD) direction is more likely to occur during stretching in the TD direction, which may result in breakage. On the other hand, if the value of MFRc / MFRs2 is too large, uneven stretching in the machine direction (MD) is likely to occur during stretching in the machine direction (MD), which could result in breakage. It is preferable that the fluidities (calculated MFR) of the base material layer 20 and the surface layer B are similar, and even if they are different, as long as they are within a certain range, that is, the relationship 0.3<MFRc / MFRs2<1.9 is satisfied, the occurrence of breakage due to uneven stretching during stretching is suppressed, allowing for stable stretching processing and improving suitability for film formation.

[0052] In a laminate film of at least three layers including a base layer 20, a surface layer A, and a surface layer B, if either the relationship between the calculated MFRs of the base layer 20 and the surface layer A (0.3 < MFRc / MFRs1 < 1.9) or the relationship between the calculated MFRs of the base layer 20 and the surface layer B (0.3 < MFRc / MFRs2 < 1.9) is not satisfied, it may be difficult to obtain good film-forming suitability. In the biaxially oriented polyethylene film 10A of the present invention, by satisfying both the relationship between the calculated MFRs of the base layer 20 and the surface layer A (0.3 < MFRc / MFRs1 < 1.9) and the relationship between the calculated MFRs of the base layer 20 and the surface layer B (0.3 < MFRc / MFRs2 < 1.9), the occurrence of breakage during stretching due to uneven stretching is suppressed, and good film-forming suitability can be obtained.

[0053] Figure 3 shows a laminate film 50 using the biaxially oriented polyethylene film of the present invention. The illustrated laminate film 50 is an example in which a base film is a biaxially oriented polyethylene film 10A of at least three layers having surface layers A and B, and a sealant film 60 is laminated via an inorganic vapor deposition layer 30 provided on the surface layer B side of the biaxially oriented polyethylene film 10A. The base film of the laminate film 50 is not limited to the illustrated biaxially oriented polyethylene film 10A, and any biaxially oriented polyethylene film according to the present invention, such as the biaxially oriented polyethylene film 10 shown in Figure 1, can also be used as appropriate. Furthermore, the sealant film 60 laminated on the base film is not limited to the illustrated example, and can be provided as appropriate, for example, on the surface layer A side.

[0054] The sealant film 60 is a heat-sealable film made of polyethylene resin. The polyethylene resin used in the sealant film 60 can be selected from, for example, linear low-density polyethylene resin (LLDPE), high-density polyethylene (HDPE), low-density polyethylene (LDPE), and the like, either singly or in combination. Because the main raw material of the sealant film 60 is the same type of polyethylene resin as the biaxially oriented polyethylene film 10A that serves as the base film, the laminate film 50 can be considered a single material (monomaterial). This makes the laminate film 50 easy to recycle.

[0055] In the laminate film 50, other polyethylene films or other functional layers such as printed layers or adhesive layers may be provided on the surface layer A side or the surface layer B side as needed. The other polyethylene films are films that are laminated to improve the rigidity and other functions of the laminate film 50. Since these polyethylene films are composed of the same type of polyethylene resin as the biaxially oriented polyethylene film 10A that serves as the base film, they are made of a single material (monomaterial), making them easy to recycle. Furthermore, the other polyethylene films can be selected from unstretched, uniaxially oriented, and biaxially oriented films depending on the purpose, but it is preferable to select a uniaxially oriented film or a biaxially oriented film from the perspective of the rigidity of the laminate film 50.

[0056] The printing layer is a layer on which any desired printed pattern such as letters, numbers, pictures, or figures is formed in order to impart design or aesthetic appeal such as decoration, or to display various other information such as the contents, shelf life, manufacturer or seller, etc. This printing layer is formed by a known processing method such as screen printing, flexographic printing, offset printing, or gravure printing, and includes appropriate printing states such as full-surface printing (solid printing) or partial printing.

[0057] The adhesive layer is a layer for adhering the various layers together, and can be formed by known methods such as dry lamination, non-solvent lamination, melt extrusion lamination, etc. Suitable adhesives for use in the adhesive layer include known adhesives such as polyurethane adhesives, polyester polyurethane adhesives, and polyether polyurethane adhesives.

[0058] In the laminate film 50, the order in which the inorganic vapor deposition layer 30, printed layer, adhesive layer, other polyethylene film, and other layers are stacked can be set as appropriate as long as the functionality of each layer is not impaired. For example, the stacking order may be such that a printed layer is provided on the surface layer B side of the biaxially oriented polyethylene film 10A, followed by the inorganic vapor deposition layer 30. In this way, the laminate film 50 can be imparted with various functionalities depending on the application, etc., and is a promising alternative to existing laminate films.

[0059] The present invention can also produce a package using the laminate film. This package is easy to recycle because it is made of a single material (mono-material) laminate film, and is therefore a promising alternative to existing packages.

[0060] [Preparation of Biaxially Stretched Polyethylene Film] The materials described below were blended in predetermined proportions (wt %), and biaxially oriented polyethylene films of Prototype Examples 1 to 24, each consisting of two layers (surface layer A and base layer) or three layers (surface layer A, base layer, and surface layer B), were prepared according to the following procedure. First, the materials were fed into an extrusion device, melted, kneaded, and formed into a sheet using a T-die method, co-extrusion of two layers (surface layer A and base layer) or co-extrusion of three layers (surface layer A, base layer, and surface layer B) to a thickness of 20 μm after biaxial stretching. In this case, the layer thickness (layer ratio) of each layer relative to the total thickness was adjusted to surface layer A:base layer = 1:19 in the case of two layers, and to surface layer A:base layer:surface layer B = 1:18:1 in the case of three layers. Subsequently, the co-extruded sheet was stretched 5 times in the machine direction (MD) by roll-to-roll stretching and 8 times in the transverse direction (TD) by tenter stretching, and then the surface of the surface layer A was subjected to a corona treatment to obtain a biaxially stretched film. The materials used for each layer in Prototype Examples 1 to 24 are shown in Tables 1 to 4 below. The stretching conditions were a machine direction (MD) roll stretching temperature of 115°C, a transverse direction (TD) preheating temperature of 143 to 145°C, and a stretching temperature of 122°C.

[0061] The following resins were used as the constituent materials of the surface layer A, the base layer, and the surface layer B. The melt flow rate (MFR) of each material was measured at 190°C and 2.16 kg in accordance with JIS K 7210 (2014). The density of the additive was the density of the base resin.

[0062] [Resin material] PE1: polyethylene resin (manufactured by The Dow Chemical Company; "TF80"), MFR: 1.7 g / 10 min, density 0.926 g / cm ３ PE2: polyethylene resin (manufactured by Prime Polymer Co., Ltd.; "SP4020"), MFR: 1.7 g / 10 min, density 0.937 g / cm ３ PE3: polyethylene resin (manufactured by Ube Maruzen Polyethylene Co., Ltd.; “4040F”), MFR: 4.2 g / 10 min, density 0.937 g / cm ３ PE4: Polyethylene resin (manufactured by Mitsui Chemicals, Inc.; "A-4085S"), MFR: 3.6 g / 10 min, density 0.885 g / cm ３PE5: polyethylene resin (manufactured by Ube Maruzen Polyethylene Co., Ltd.; “021GT”), MFR: 6.8 g / 10 min, density 0.919 g / cm ３ PE6: polyethylene resin (manufactured by Ube Maruzen Polyethylene Co., Ltd.; "031GLD"), MFR: 9.1 g / 10 min, density 0.913 g / cm ３ PE7: Polyethylene resin (manufactured by Mitsui Chemicals, Inc.; "A-20085S"), MFR: 18.5 g / 10 min, density 0.885 g / cm ３ PE8: Polyethylene resin (manufactured by Mitsui Chemicals, Inc.; "A-20090S"), MFR: 18.2 g / 10 min, density 0.893 g / cm ３

[0063] [Additives] AB1: A 5 wt% concentration antiblocking agent masterbatch obtained by compounding 5 wt% of an antiblocking agent (manufactured by Fuji Silysia Chemical Ltd.; "Sylysia 430") and 95 wt% of a base resin (polyethylene resin: manufactured by Dow Chemical Company; "TF80"), MFR: 1.6 g / 10 min, density 0.926 g / cm ３ AS1: A 10 wt% concentration antistatic masterbatch obtained by compounding 10 wt% of a mixed material obtained by mixing surfactant 1 (manufactured by Toho Chemical Industry Co., Ltd.; "SA-20B") and surfactant 2 (manufactured by Toho Chemical Industry Co., Ltd.; "MG-100VP") in a weight ratio of 1:2 with 90 wt% of a base resin (polyethylene resin: manufactured by Dow Chemical Company; "TF80"), MFR: 2.9 g / 10 min, density 0.926 g / cm ３

[0064] [Prototype Example 1] Prototype Example 1 is a three-layer film, and its composition is as follows: surface layer A is 94.0 wt% of PE1 as a polyethylene-based resin and 6.0 wt% of AB1 as an additive; base layer is 80.0 wt% of PE3 and 20.0 wt% of PE4 as polyethylene-based resins; surface layer B is 94.0 wt% of PE1 as a polyethylene-based resin and 6.0 wt% of AB1 as an additive.

[0065] [Prototype Example 2] The formulation of prototype example 2 is the same as that of prototype example 1, except that the base layer is made of a polyethylene-based resin, with PE2 at 40.0 wt%, PE3 at 40.0 wt%, and PE8 at 20.0 wt%.

[0066] [Prototype Example 3] The formulation of prototype example 3 is the same as that of prototype example 1, except that the base layer is made of a polyethylene-based resin, with PE2 at 20.0 wt%, PE3 at 60.0 wt%, and PE4 at 20.0 wt%.

[0067] [Prototype Example 4] The composition of prototype example 4 is the same as that of prototype example 3 except that the base layer is made of polyethylene-based resin, with PE2 at 26.0 wt % and PE3 at 54.0 wt %.

[0068] [Prototype Example 5] The composition of prototype example 5 is the same as that of prototype example 3 except that the polyethylene resin used for the base layer was changed to 33.0 wt % PE2 and 47.0 wt % PE3.

[0069] [Prototype Example 6] The composition of prototype example 6 is the same as that of prototype example 3 except that the base layer is made of polyethylene-based resin, with PE2 at 40.0 wt % and PE3 at 40.0 wt %.

[0070] [Prototype Example 7] Prototype Example 7 is a three-layer film, and its composition is as follows: surface layer A: polyethylene-based resins consisting of 37.6 wt% PE2, 37.6 wt% PE3, and 18.8 wt% PE7, and 6.0 wt% AB1 as an additive; base layer: polyethylene-based resins consisting of 40.0 wt% PE2, 40.0 wt% PE3, and 20.0 wt% PE7; surface layer B: polyethylene-based resins consisting of 37.6 wt% PE2, 37.6 wt% PE3, and 18.8 wt% PE7, and 6.0 wt% AB1 as an additive.

[0071] [Prototype Example 8] The formulation of prototype example 8 is the same as that of prototype example 7, except that PE7 in surface layer A is changed to PE8, PE7 in the base material layer is changed to PE8, and PE7 in surface layer B is changed to PE8, with the rest remaining the same.

[0072] [Prototype Example 9] The formulation of prototype example 9 is the same as that of prototype example 1, except that the base layer is made of a polyethylene-based resin and PE1 is 100.0% by weight.

[0073] [Prototype Example 10] The formulation of prototype example 10 is the same as that of prototype example 9, except that the surface layer A contains 84.0 wt% PE1 and 10.0 wt% PE4 as polyethylene-based resins, the base material layer contains 97.0 wt% PE1 as polyethylene-based resins and 3.0 wt% AS1 as an additive, and the surface layer B contains 84.0 wt% PE1 and 10.0 wt% PE4 as polyethylene-based resins.

[0074] [Prototype Example 11] The formulation of prototype example 11 is the same as that of prototype example 10, except that the PE1 content in surface layer A is changed to 64.0 wt % and the PE4 content to 30.0 wt %, and the PE1 content in surface layer B is changed to 64.0 wt % and the PE4 content to 30.0 wt %.

[0075] [Prototype Example 12] The formulation of prototype example 12 is the same as that of prototype example 10, except that the PE1 content in surface layer A is changed to 49.0 wt % and the PE4 content to 45.0 wt %, and the PE1 content in surface layer B is changed to 49.0 wt % and the PE4 content to 45.0 wt %.

[0076] [Prototype Example 13] The formulation of prototype example 13 is the same as that of prototype example 10, except that the PE1 content in surface layer A is changed to 34.0 wt % and the PE4 content to 60.0 wt %, and the PE1 content in surface layer B is changed to 34.0 wt % and the PE4 content to 60.0 wt %.

[0077] [Prototype Example 14] The formulation of prototype example 14 is an example in which the formulation of prototype example 9 is changed such that surface layer A is a polyethylene-based resin containing 37.6 wt% PE2, 37.6 wt% PE3, 9.4 wt% PE4, and 9.4 wt% PE7, and surface layer B is a polyethylene-based resin containing 37.6 wt% PE2, 37.6 wt% PE3, 9.4 wt% PE4, and 9.4 wt% PE7, but the rest is the same.

[0078] [Prototype Example 15] The formulation of prototype example 15 is the same as that of prototype example 14, except that the surface layer A is made of a polyethylene-based resin containing 37.0 wt% PE2, 37.0 wt% PE3, and 20.0 wt% PE7, and the surface layer B is made of a polyethylene-based resin containing 37.0 wt% PE2, 37.0 wt% PE3, and 20.0 wt% PE7, but the rest of the formulation is the same.

[0079] [Prototype Example 16] The composition of prototype example 16 is the same as that of prototype example 9, except that PE1 in surface layer A is changed to PE5, and PE1 in surface layer B is changed to PE5.

[0080] [Prototype Example 17] The composition of prototype example 17 is the same as that of prototype example 9, except that PE1 in surface layer A is changed to PE6, and PE1 in surface layer B is changed to PE6.

[0081] [Prototype Example 18] The composition of the prototype example 18 is the same as that of the prototype example 16, except that PE5 in the surface layer B is changed to PE1.

[0082] [Prototype Example 19] The composition of the prototype example 19 is the same as that of the prototype example 18, except that PE5 in the surface layer A is changed to PE6.

[0083] [Prototype Example 20] The formulation of prototype example 20 is the same as that of prototype example 4, except that the surface layer B is made of a polyethylene-based resin, with PE2 at 20.0 wt%, PE3 at 55.2 wt%, and PE4 at 18.8 wt%, except that the formulation is the same as prototype example 4.

[0084] [Prototype Example 21] The formulation of prototype example 21 is the same as that of prototype example 3, except that the surface layer B is made of a polyethylene-based resin, with PE2 at 14.0 wt%, PE3 at 61.2 wt%, and PE4 at 18.8 wt%.

[0085] [Prototype Example 22] The formulation of prototype example 22 is the same as that of prototype example 11, except that the base layer is made of a polyethylene-based resin containing 87.0 wt% PE1 and 10.0 wt% PE4, and the surface layer B is made of a polyethylene-based resin containing 94.0 wt% PE1.

[0086] [Prototype Example 23] Prototype Example 23 is a two-layer film, and its composition is as follows: surface layer A is 94.0 wt% PE1 as a polyethylene-based resin and 6.0 wt% AB1 as an additive; and base layer is 100.0 wt% PE1 as a polyethylene-based resin.

[0087] [Prototype Example 24] Prototype Example 24 is a two-layer film, and its composition is as follows: surface layer A is 54.0 wt% PE1 and 40.0 wt% PE4 as polyethylene-based resins, and 6.0 wt% AB1 as an additive; and base layer is 94.0 wt% PE1 as a polyethylene-based resin, and 6.0 wt% AB1 as an additive.

[0088]

[0089]

[0090]

[0091]

[0092] [Calculated Density] For the polyethylene films of Samples 1 to 22, the calculated density (g / cm 3 ) of each of the surface layer A, the base layer, and the surface layer B was ３ In addition, for the polyethylene films of Samples 23 and 24, the calculated density (g / cm ３ The calculated density is calculated using the following formula (i) based on the density and blending ratio of each constituent material used in the target layer.

[0093]

[0094] The symbols in formula (i) are as follows: P: calculated density of the target layer (g / cm ３ ) n: total number of resins constituting the target layer wk: blending ratio of resin k constituting the target layer ρk: density (g / cm ３ )

[0095] [Calculated MFR] For the polyethylene films of Prototype Examples 1 to 22, the calculated MFR (g / 10 min) was calculated for each of the surface layer A, base layer, and surface layer B. For the polyethylene films of Prototype Examples 23 and 24, the calculated MFR (g / 10 min) was calculated for each of the surface layer A and base layer. The calculated MFR is calculated using the following formula (ii) based on the MFR and blending ratio of each constituent material used in the target layer. The calculated MFR of the surface layer A was MFRs1, the calculated MFR of the base layer was MFRc, and the calculated MFR of the surface layer B was MFRs2. The relationship between the calculated MFRs of the base layer and surface layer A was expressed as MFRc / MFRs1, and the relationship between the calculated MFRs of the base layer and surface layer B was expressed as MFRc / MFRs2.

[0096]

[0097] The symbols in formula (ii) are as follows. The logarithm in formula (ii) is a common logarithm. MFRx: calculated MFR (g / 10 min) of the target layer; n: total number of resins constituting the target layer; wk: blending ratio of resin k constituting the target layer; MFRk: MFR (g / 10 min) of resin k constituting the target layer.

[0098] [Evaluation] The polyethylene films of Prototype Examples 1 to 24 were evaluated as "poor (x)" when breakage occurred during the stretching treatment (film formation was not possible), and as "good (◯)" when a biaxially stretched film was properly formed during the stretching treatment (film formation was possible). The calculated density and calculated MFR of each layer and the film formation evaluation for Prototype Examples 1 to 24 are shown in Tables 5 to 8 below.

[0099]

[0100]

[0101]

[0102]

[0103] [Results and Discussion] As can be seen from Tables 5 to 8, when the polyethylene films of Prototype Examples 1 to 24 were stretched, breakage occurred in Prototype Examples 1 to 4 and 16 to 21, preventing them from being formed into films, while biaxially oriented polyethylene films were properly formed in Prototype Examples 5 to 15 and 22 to 24. In particular, Prototype Examples 1 to 4, 20, and 21 broke during stretching in the transverse (TD) direction due to uneven stretching that occurred during stretching in the longitudinal (MD) direction, while Prototype Examples 16 to 19 broke during stretching in the transverse (TD) direction due to uneven stretching in the TD.

[0104] Here, regarding prototypes 1 to 17, which are three-layer films in which surface layer A and surface layer B have the same structure, prototypes 5 to 15, which were properly formed into films, were compared with prototypes 1 to 4, 16, and 17, which broke during the transverse (TD) direction stretching treatment, and the physical properties (calculated density, calculated MFR) of the constituent materials were examined.

[0105] First, looking at the calculated density of prototypes 1 to 17, for example, the calculated density of each layer was approximately the same in prototypes 3 to 6, and no difference in calculated density was observed between prototypes 3 and 4, which could not be made into a film, and prototypes 5 and 6, which could be made into a film. Furthermore, even when looking at the calculated density and film-making evaluation results for the other prototypes 1, 2, and 7 to 17, no relationship between calculated density and film-making could be found.

[0106] On the other hand, looking at the calculated MFRs of Prototype Examples 1 to 17, film formation was not possible when the value of MFRc / MFRs1, which indicates the relationship between the calculated MFRs of the base layer and the surface layer A, or the value of MFRc / MFRs2, which indicates the relationship between the calculated MFRs of the base layer and the surface layer B, was 1.9 or more (Prototype Examples 1 to 4) or 0.3 or less (Prototype Examples 16 and 17). In particular, when the value of MFRc / MFRs1 or the value of MFRc / MFRs2 was 1.9 or more (Prototype Examples 1 to 4), the film broke during transverse (TD) stretching due to uneven stretching in the machine direction (MD) that occurred during stretching in the machine direction, and when the value was 0.3 or less (Prototype Examples 16 and 17), the film broke during transverse (TD) stretching due to uneven stretching in the transverse direction.

[0107] A large value of MFRc / MFRs1 or MFRc / MFRs2 indicates that the MFR of the base layer is higher than the MFR of the surface layer A or B, that is, that the fluidity of the resin in the base layer is higher than the fluidity of the resin in the surface layer A or B. In Samples 1 to 4, in which breakage occurred during stretching in the transverse (TD) direction, it is believed that the breakage occurred because the MFR (fluidity) of the base layer was excessively higher than that of the surface layer A or B, making it easier for uneven stretching in the longitudinal (MD) direction to occur during stretching in the MD direction.

[0108] Furthermore, a small value of MFRc / MFRs1 or MFRc / MFRs2 indicates that the MFR of the base material layer is lower than the MFR of the surface layer A or B, that is, that the fluidity of the resin in the base material layer is lower than the fluidity of the resin in the surface layer A or B. In Samples 16 and 17, which broke during stretching in the transverse (TD) direction, it is believed that the break occurred because the MFR (fluidity) of the base material layer was excessively lower than that of the surface layer A or B, making it easier for uneven stretching in the transverse (TD) direction to occur.

[0109] In contrast, in Prototype Examples 5 to 15, which were successfully formed into films, the MFRc / MFRs1 and MFRc / MFRs2 values ​​all fell within a certain range. This indicates that the fluidity of the base layer and the surface layer A or B was relatively similar. Therefore, it is believed that when the MFRs (fluidity) of the base layer and the surface layer A or B are relatively similar, stable stretching processing becomes possible and appropriate film formation can be achieved. From each prototype, it is believed that the preferred MFR (fluidity) relationship between the base layer and the surface layer A or B is 0.3 < MFRc / MFRs1 < 1.9 for the base layer (MFRc) and the surface layer A (MFRs1), and 0.3 < MFRc / MFRs2 < 1.9 for the base layer (MFRc) and the surface layer B (MFRs2).

[0110] Next, we will consider Prototype Examples 18 to 22, which are three-layer films in which the surface layer A and the surface layer B have different compositions. In Prototype Examples 18 to 21, in which fracture occurred, the MFR relationship (MFRc / MFRs2) between the base layer and the surface layer B was within the above-mentioned range, but the MFR relationship (MFRc / MFRs1) between the base layer and the surface layer A was outside the above-mentioned range. In contrast, in Prototype Example 22, which was properly formed into a film, the MFR relationships (MFRc / MFRs1, MFRc / MFRs2) between the base layer and the surface layer A and between the base layer and the surface layer B were both within the above-mentioned range. From this, it can be seen that even when the surface layers A and B have different compositions, proper film formation is possible if the MFR relationships (MFRc / MFRs1, MFRc / MFRs2) between the base layer and each surface layer satisfy the above-mentioned conditions. On the other hand, it is considered that proper film formation is difficult if the above-mentioned conditions are not satisfied.

[0111] As described above, it has been shown that a polyethylene film consisting of at least three layers, i.e., a base layer and surface layers A and B, can be stably formed into a film when the base layer and surface layer A satisfy the relationship 0.3<MFRc / MFRs1<1.9 and the base layer and surface layer B satisfy the relationship 0.3<MFRc / MFRs2<1.9. Therefore, MFRc / MFRs1, which indicates the relationship between the calculated MFRs of the base layer and surface layer A, and MFRc / MFRs2, which indicates the relationship between the calculated MFRs of the base layer and surface layer B, can be said to be useful as indicators of the stretchability (film-forming suitability) of a polyethylene film.

[0112] In addition, in Samples 23 and 24, which are two-layer films consisting of a base layer and a surface layer A, the MFR relationship values ​​were within the range of 0.3<MFRc / MFRs1<1.9, and they were able to be appropriately formed into a film. Therefore, it is thought that in a polyethylene film consisting of two layers, a base layer and a surface layer A, if the base layer and the surface layer A satisfy the relationship of 0.3<MFRc / MFRs1<1.9, they can be stably formed into a film.

[0113] As described above, in the biaxially oriented polyethylene film of the present invention, in a two-layer laminate film made primarily of a single material (mono-material) based on polyethylene resin, good stretchability is achieved when the relationship between the calculated MFR (MFRc) of the base layer and the calculated MFR (MFRs1) of the surface layer A satisfies 0.3 < MFRc / MFRs1 < 1.9. Furthermore, in a laminate film of at least three layers, good stretchability is achieved when the relationship between the calculated MFR (MFRc) of the base layer and the calculated MFR (MFRs1) of the surface layer A satisfies 0.3 < MFRc / MFRs1 < 1.9, and when the relationship between the calculated MFR (MFRc) of the base layer and the calculated MFR (MFRs2) of the surface layer B satisfies 0.3 < MFRc / MFRs2 < 1.9. Therefore, a biaxially oriented polyethylene film made of a single material can be provided more reliably than before.

[0114] 10, 10A Biaxially oriented polyethylene film 20 Base layer 30 Inorganic vapor deposition layer 50 Laminate film 60 Sealant film A Surface layer B Surface layer

Claims

1. A biaxially oriented polyethylene film comprising a base layer and a surface layer A disposed on one side of the base layer, stretched in two axial directions, the machine direction (MD) and the transverse direction (TD), wherein the base layer is primarily composed of a polyethylene resin, and the relationship between the calculated MFR (MFRc) of the base layer and the calculated MFR (MFRs1) of the surface layer A satisfies 0.3<MFRc / MFRs1<1.

9.

2. A biaxially oriented film consisting of at least three layers, including a base layer, a surface layer A arranged on one side of the base layer, and a surface layer B arranged on the other side of the base layer, and stretched in two axial directions, the machine direction (MD) and the transverse direction (TD), wherein the base layer is mainly composed of a polyethylene resin, and the relationship between the calculated MFR (MFRc) of the base layer and the calculated MFR (MFRs1) of the surface layer A satisfies 0.3 < MFRc / MFRs1 < 1.9, and the relationship between the calculated MFR (MFRc) of the base layer and the calculated MFR (MFRs2) of the surface layer B satisfies 0.3 < MFRc / MFRs2 < 1.

9.

3. The biaxially oriented polyethylene film according to claim 1, wherein an inorganic vapor deposition layer is disposed on the surface layer A side.

4. The biaxially oriented polyethylene film according to claim 2, wherein at least one of the surface layer A and the surface layer B is provided with an inorganic vapor-deposited layer.

5. The biaxially oriented polyethylene film according to claim 1, wherein the surface layer A is mainly composed of a polyethylene resin.

6. The biaxially oriented polyethylene film according to claim 2, wherein the surface layer A and / or the surface layer B is mainly composed of a polyethylene resin.

7. A laminate film characterized by comprising the biaxially oriented polyethylene film according to claim 1 or 2 and a sealant film made of at least a polyethylene resin laminated thereon.

8. A laminate film characterized by comprising the biaxially oriented polyethylene film according to claim 3 or 4 and a sealant film made of at least a polyethylene resin laminated thereon.

9. A package comprising the laminate film according to claim 7.

10. A package comprising the laminate film according to claim 8.

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