Laminated film, packaging material, and method for manufacturing laminated film

Abstract

The present invention provides a laminated film and packaging material that are highly recyclable and have good oxygen barrier properties because they do not use an anchor coat layer or adhesive, as well as a method for manufacturing a laminated film. [Solution] The laminated film 10 according to this embodiment comprises an olefin resin film 20 and a transparent vapor-deposited layer 40 laminated in direct contact with the olefin resin film 20. The olefin resin film 20 comprises at least a core layer 30 and a surface layer 31 in this order. The transparent vapor-deposited layer 40 and the surface layer 31 are adjacent to each other, and the surface layer 31 contains metal oxide particles 32, with a portion of the surface of the metal oxide particles 32 exposed from the surface layer 31.

Description

Technical Field

[0001] The present invention relates to a laminated film, a packaging material, and a method for manufacturing a laminated film.

Background Art

[0002] Generally, plastic films have properties such as being lightweight, chemically stable, easy to process, flexible and strong, and capable of mass production. Therefore, plastic films are used in various applications. Examples of the uses of plastic films include packaging materials for packaging food products, pharmaceuticals, etc., drip packs, shopping bags, posters, tapes, optical films used in liquid crystal televisions, etc., protective films, window films adhered to windows, vinyl greenhouses, building materials, and so on, covering a wide range. For such applications, an appropriate plastic material is selected according to the application.

[0003] For example, in packaging materials, a resin film excellent in strength and heat resistance such as a polyester film or a nylon film is used as a base film, and on top of that, a resin film excellent in flexibility and heat sealability at low temperatures such as polyethylene or polypropylene is used as a sealant film (or a heat seal layer) and laminated, and such laminated films are widely used. By using a plurality of different plastics, namely the base film and the sealant film, when heat-sealing with the sealant film side inside, a packaging bag can be obtained in which the inside is sufficiently fused and the outside does not undergo deformation such as wrinkles.

[0004] Also, in packaging materials for food, in order to suppress the deterioration of the contents and extend the expiration date, a barrier resin is laminated or a vapor deposition film is laminated. For example, in the technique described in Patent Document 1, after applying a primer layer on a stretched base material, a vapor deposition film is laminated to improve the barrier property. The primer layer in the technique described in Patent Document 1 ensures the flatness of the base material surface and contributes to the improvement of the barrier property.

[0005] On the other hand, in recent years, there has been a growing demand for the realization of a sustainable society, and the recycling of packaging materials is also desired. From this perspective, technologies are being developed to separate conventional laminated films, which consist of multiple materials, into individual resin materials. However, this method has the problem that, in order to achieve good recycling, impurities must be removed precisely, which takes a lot of time, energy, and cost. In addition, cross-linking substances such as adhesives and primers are difficult to remove because they are present in small amounts, and can become a source of defects as gels during recycling. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2023-118619 [Overview of the project] [Problems that the invention aims to solve]

[0007] Although the substrate described in Patent Document 1 above is made up of the same type of resin film with recyclability in mind, it also has a crosslinked material (a compound polymer in which resins are crosslinked) such as a primer layer laminated on top of it, and it is conceivable that when the above laminate is recycled, the crosslinked material may become a foreign substance. Thus, in the field of technology encompassing laminates and packaging materials, it has been difficult to achieve both excellent oxygen barrier properties and excellent recyclability using conventional technologies.

[0008] The present invention has been made in view of the above circumstances, and aims to provide a laminated film and packaging material that is highly recyclable and has good oxygen barrier properties because it does not use an anchor coat layer or adhesive, as well as a method for manufacturing a laminated film. [Means for solving the problem]

[0009] This disclosure relates to the following [1] to [6]. [1] comprising an olefin resin film and a transparent vapor-deposited layer laminated in direct contact with the olefin resin film, The olefin resin film comprises at least a core layer and a surface layer in this order. The transparent vapor deposition layer and the surface layer are adjacent to each other. The aforementioned surface layer contains metal oxide particles, A laminated film characterized in that a portion of the surface of the metal oxide particles is exposed from the surface layer. [2] The core layer is mainly composed of homopolypropylene, The laminated film according to [1], characterized in that the surface layer is mainly composed of random polypropylene. [3] The laminated film according to [1], characterized in that the olefin resin film is a biaxially oriented film. [4] The laminated film according to [1], characterized in that the surface layer further contains a compatibilizer. [5] A laminated film as described in any of [1] to [4], A coating layer formed of a barrier material is laminated on the transparent vapor-deposited layer, A packaging material characterized by comprising a heat-seal layer mainly composed of random polypropylene on the side of the olefin resin film opposite to the transparent vapor-deposited layer. A method for manufacturing a laminated film according to any one of [6] [1] to [4], A step of forming the olefin resin film such that the metal oxide particles are exposed from the surface layer, After forming the olefin resin film, the process involves performing plasma treatment on the surface of the surface layer, A method for manufacturing a laminated film, characterized by having a step of forming the transparent vapor deposition layer after performing the plasma treatment. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a laminated film, a packaging material, and a method for producing a laminated film that are excellent in recyclability because they do not use an anchor coat layer or an adhesive and have good oxygen barrier properties.

Brief Description of the Drawings

[0011] [Figure 1] It is a cross-sectional view schematically showing an example of the laminated film of the present embodiment. [Figure 2] It is a cross-sectional view schematically showing an example of the laminated film of the present embodiment. [Figure 3] It is a cross-sectional view schematically showing another example of the laminated film of the present embodiment. [Figure 4] It is a cross-sectional view schematically showing an example of the packaging material of the present embodiment.

Modes for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Each figure is a schematically shown figure, and the size, shape, etc. of each part are exaggerated as appropriate for easy understanding. Also, for simplicity of explanation, the same reference numerals are given to corresponding parts in each figure.

[0013] [Laminated Film] The laminated film 10 of the present embodiment includes an olefin resin film 20 and a transparent vapor deposition layer 40 laminated directly on the olefin resin film 20. The olefin resin film 20 includes at least a core layer 30 and a surface layer 31 in this order. The transparent vapor deposition layer 40 and the surface layer 31 are adjacent to each other. The surface layer 31 contains metal oxide particles 32, and a part of the surface of the metal oxide particles 32 is exposed from the surface of the surface layer 31. Further, it is preferable that the surface layer 31 located on the transparent vapor deposition layer 40 side of the olefin resin film 20 contains a polypropylene resin.

[0014] By having the above-described configuration, the laminated film 10 of the present embodiment does not use an anchor coat layer or an adhesive that can cause the generation of crosslinked products, and thus is excellent in recyclability and can have good oxygen barrier properties. Although the reason for such an effect is not clearly understood, the present inventors speculate as follows.

[0015] Since the laminated film 10 of the present embodiment does not provide an anchor coat layer or an adhesive between the surface layer 31 and the transparent vapor deposition layer 40, the transparent vapor deposition layer 40 directly contacts a part of the metal oxide particles 32 exposed from the surface of the surface layer 31. Here, because the metal oxide particles 32 having a composition material and physical properties similar to those of the transparent vapor deposition layer 40 are present in the surface layer 31, the affinity between the metal oxide particles 32 and the transparent vapor deposition layer 40 is increased, and it is considered that a dense film is formed and the barrier property (particularly the oxygen barrier property) is enhanced. That is, it is considered that a chemical interaction such as crosslinking or hydrogen bonding between the metal oxide particles 32 and the vapor deposition material constituting the transparent vapor deposition layer 40 acts between the metal oxide particles 32 and the transparent vapor deposition layer 40. As another factor, it is generally known that when the smoothness of the surface of the surface layer 31 in contact with the transparent vapor deposition layer 40 is poor and particularly there are steep irregularities, the oxygen barrier property deteriorates. However, the metal oxide particles 32 added to the surface layer 31 serve to smooth the steep irregularities that can be formed on the surface of the surface layer 31. Therefore, in the case of the laminated film 10 of the present embodiment, it is considered that the defects of the transparent vapor deposition layer 40 are reduced and the oxygen barrier property is improved.

[0016] Furthermore, the laminated film 10 of this embodiment solves the following problem of adhesives and anchor coat layers becoming foreign matter when recycled without separating each layer, by having a laminated structure without using adhesives or anchor coat layers. Specifically, since adhesives and anchor coat layers are usually crosslinked in three dimensions, it has been found that laminated films using conventional technology that use adhesives and anchor coat layers tend to become foreign matter when reused as recycled material. It has also been found that even if the content of adhesives and anchor coat layers in the laminated film is relatively small, if the adhesives and anchor coat layers have crosslinked resin components, it is difficult to finely disperse them during recycling, and the crosslinked resin components tend to become foreign matter. And recycled material contaminated with such foreign matter can lead to fisheyes and a decrease in physical properties. In this disclosure, "adhesive" and "anchor coat layer" refer to a resin material used to bond two layers with different physical properties, such as a two-component curing type urethane adhesive material.

[0017] Figures 1 and 2 are schematic cross-sectional views showing an example of the laminated film 10 of this embodiment. In the laminated film 10 shown in Figures 1 and 2, an olefin resin film 20 and a transparent vapor-deposited layer 40 are laminated in direct contact without an adhesive or anchor coat layer. The olefin resin film 20 has a surface layer 31 on the transparent vapor-deposited layer 40 side, and the surface layer 31 is made of a resin containing polypropylene resin. The surface layer 31 also contains metal oxide particles 32, and a portion of the surface of the metal oxide particles 32 is exposed from the surface of the surface layer 31. As shown in Figure 1, in this embodiment, it is not necessary for a portion of the surface of all metal oxide particles 32 added to the surface layer 31 to be exposed, or as shown in Figure 2, a portion of the surface of all metal oxide particles 32 added to the surface layer 31 may be exposed.

[0018] In other words, as shown in Figure 1, of the metal oxide particles 32 added to the surface layer 31, some of the metal oxide particles 32 may be partially exposed from the surface of the surface layer 31, while other metal oxide particles 32 may remain embedded within the surface layer 31 without being exposed. Specifically, the proportion of metal oxide particles 32 partially exposed from the surface layer 31 is preferably 10% by mass or more, more preferably 30% by mass or more, and even more preferably 50% by mass or more, relative to the total mass of metal oxide particles 32 added to the surface layer 31. If the proportion of metal oxide particles 32 partially exposed from the surface layer 31 is within the above range, a chemical interaction will effectively function between the metal oxide particles 32 and the transparent vapor deposition layer 40, as will be described later, and a high bonding strength will be obtained. Furthermore, the configuration shown in Figure 2 corresponds to the case where the proportion of metal oxide particles 32 whose surface is partially exposed from the surface layer 31 is 100% by mass relative to the total mass of metal oxide particles 32 added to the surface layer 31.

[0019] Furthermore, the amount of exposure (percentage of exposure) of the metal oxide particles 32 from the surface layer 31 is preferably such that the ratio of carbon atoms to aluminum atoms (Al / C), measured by X-ray photoelectron spectroscopy (XPS) assuming the metal oxide particles 32 are aluminum oxide, is 0.001 or higher, more preferably 0.02 or higher, and even more preferably 0.1 or higher. If the amount of exposure is within the above range, a portion of the metal oxide particles 32 is appropriately exposed from the surface of the surface layer 31, so that, as will be described later, chemical interactions work effectively between the metal oxide particles 32 and the transparent vapor deposition layer 40, and a high bonding strength is obtained. In this embodiment, the ratio of carbon atoms to aluminum atoms (Al / C) was calculated from the peak area attributable to aluminum atoms and the peak area attributable to carbon atoms, as measured by X-ray photoelectron spectroscopy (XPS). Furthermore, a larger ratio of carbon atoms to aluminum atoms (Al / C) means that a larger amount of the metal oxide particles 32 are exposed from the surface layer 31.

[0020] Examples of resins (constituent resins) constituting the surface layer 31 of the olefin resin film 20 include polypropylene resins such as homopolypropylene, block polypropylene, and random polypropylene, as well as propylene-α-olefin copolymers. Preferably, random polypropylene is used. When random polypropylene is the main component of the resin constituting the surface layer 31, the degree of crystallinity is relatively low, making it easy to create a smooth surface without steep irregularities, which makes it less likely for defects to occur when the transparent vapor deposition layer 40 is formed, and thus improves barrier properties. The surface layer 31 may contain a single random polypropylene resin, or it may contain multiple polypropylene resins with different melting points, MFRs, etc.

[0021] In this embodiment, the term "main component" refers to a resin component that makes up 50% by mass or more of the total mass of the resin components constituting the surface layer 31. In other words, in this embodiment, it is preferable that the mass of random polypropylene is 50% by mass or more of the total mass of the resin components constituting the surface layer 31, more preferably 80% by mass or more, even more preferably 90% by mass or more, and most preferably 100% by mass.

[0022] As the resin (constituent resin) constituting the core layer 30 of the olefin resin film 20, olefin resins such as low-density polyethylene, linear low-density polyethylene, high-density polyethylene, homopolypropylene, block polypropylene, random polypropylene, ethylene-vinyl alcohol copolymer, cyclic olefin copolymer, and blends of two or more of these can be used. Preferably, homopolypropylene, block polypropylene, or random polypropylene of the same type as the resin of the surface layer 31 is used. Using the same type of polypropylene significantly improves recyclability. Even more preferably, homopolypropylene with strength and heat resistance as a base material is used.

[0023] In other words, in this embodiment, it is preferable from the viewpoint of recyclability that the main component of the resin constituting the core layer 30 is homopolypropylene. In this embodiment, the term "main component" refers to a resin component that makes up 50% by mass or more of the total mass of the resin components constituting the core layer 30. In other words, in this embodiment, it is preferable that the mass of homopolypropylene is 50% by mass or more of the total mass of the resin components constituting the core layer 30, more preferably 80% by mass or more, even more preferably 90% by mass or more, and most preferably 100% by mass.

[0024] Examples of metal oxide particles 32 include alumina, silica, copper oxide, titanium oxide, and zinc oxide. At least some of the metal oxide particles 32 contained in the surface layer 31 are exposed on the surface of the surface layer 31, and it is thought that they act chemically with the laminated transparent vapor deposition layer 40 to form a dense film and improve barrier properties. The surface treatment of the metal oxide particles 32 is not particularly limited, but a hydrophilic surface treatment is preferable because it facilitates the chemical interaction between the functional groups on the surface of the metal oxide particles 32 and the materials constituting the transparent vapor deposition layer 40.

[0025] The metal oxide particles 32 are preferably spherical or semi-spherical, having a gently curved surface, and a large radius of curvature is also preferable. With such a shape, even if there are sharp irregularities on the surface of the surface layer 31, the metal oxide particles 32 with their gently curved surfaces that are exposed on the surface will smooth out the irregularities on the surface layer 31, reducing the number of defects when the transparent vapor deposition layer 40 is formed, and preventing deterioration of barrier properties. For example, irregular shapes or porous shapes are undesirable because the metal oxide particles 32 themselves have sharp irregularities.

[0026] The size of the metal oxide particles 32 is preferably 0.1 μm or more and less than 1 μm in median diameter. If the size of the metal oxide particles 32 is less than 0.1 μm in median diameter, strong secondary aggregation of the particles occurs, resulting in the generation of many aggregates several μm in size, which can become defects. If the size of the metal oxide particles 32 is 1 μm or more in median diameter, the exposure of the metal oxide particles 32 from the surface layer 31 becomes too large, resulting in large, albeit not steep, irregularities on the surface of the surface layer 31, which is undesirable for the formation of the transparent vapor-deposited layer 40.

[0027] The thickness of the surface layer 31 is not particularly limited, but is generally preferably 0.1 μm or more and less than 10 μm, more preferably 0.3 μm or more and less than 8 μm, and even more preferably 0.5 μm or more and less than 5 μm. If the thickness of the surface layer 31 is less than 0.1 μm, it becomes too thin relative to the size of the metal oxide particles 32. As a result, the exposure of the metal oxide particles 32 on the surface of the surface layer 31 becomes too large, and large, though not steep, irregularities occur on the surface of the surface layer 31, which is undesirable for the formation of the transparent vapor deposition layer 40. If the thickness of the surface layer 31 is 10 μm or more, it becomes too large relative to the size of the metal oxide particles 32, and the metal oxide particles 32 may not be exposed on the surface. In that case, the effect of containing metal oxide particles 32 may not be expected.

[0028] The relationship between the thickness of the surface layer 31 and the size of the metal oxide particles 32 is not particularly limited, but it is preferable that the thickness of the surface layer 31 is 0.2 to 10 times the size of the metal oxide particles 32, more preferably 0.5 to 8 times, and even more preferably 1.0 to 5 times. With such a relationship, the metal oxide particles 32 are appropriately exposed from the surface layer 31, chemical interactions can easily occur between the transparent vapor deposition layer 40 and the metal oxide particles 32, and as a result, an effect of improved barrier properties can be easily obtained.

[0029] The concentration of metal oxide particles 32 within the surface layer 31, i.e., the total mass ratio of metal oxide particles 32 to the total mass of the surface layer 31 containing metal oxide particles 32 (total mass of metal oxide particles 32 / total mass of the surface layer 31 containing metal oxide particles 32), is preferably 10 wt% or more and less than 50 wt%, preferably 20 wt% or more and less than 40 wt%, and more preferably 25 wt% or more and less than 30 wt%. If the concentration of metal oxide particles 32 within the surface layer 31 is less than 10 wt%, the amount of metal oxide particles 32 exposed on the surface of the surface layer 31 may be small, resulting in a reduced effect. Furthermore, if the concentration of metal oxide particles 32 within the surface layer 31 is 50 wt% or more, it may become difficult to form the surface layer 31.

[0030] The surface of the surface layer 31 adjacent to the transparent vapor-deposited layer 40 may be subjected to surface treatment (such as plasma treatment) before laminating the transparent vapor-deposited layer 40. Plasma treatment or corona treatment modifies the surface of the resin constituting the surface layer 31, making it easier for the functional groups on the resin surface of the surface layer 31 to chemically interact with the transparent vapor-deposited film constituting the transparent vapor-deposited layer 40, thereby improving barrier properties. Furthermore, the resin covering the surface of the metal oxide particles 32 is etched, increasing the amount of metal oxide particles 32 exposed from the surface layer 31. As a result, a dramatic improvement in barrier properties is achieved.

[0031] The olefin resin film 20 may be stretched. The stretching may be uniaxial or biaxial. Stretching is preferable because it can improve the strength, heat resistance, and barrier properties of the substrate. From a productivity standpoint, sequential biaxial stretching is preferable. Furthermore, when the olefin resin film 20 is stretched, it is easier to form a thin surface layer 31, and the metal oxide particles 32 are more easily exposed on the surface. Furthermore, by adjusting the stretching ratio of the olefin resin film 20, the thickness of the surface layer 31 can be arbitrarily adjusted, thereby allowing the amount of metal oxide particles 32 exposed from the surface layer 31 to be arbitrarily adjusted.

[0032] The stretching ratio in the flow direction (MD) of the olefin resin film 20 may be within the range of 2 to 10 times, and preferably within the range of 3 to 7 times. Furthermore, the stretching ratio in the width direction (TD) of the olefin resin film 20 may be within the range of 3 to 15 times, and preferably within the range of 5 to 12 times. When the stretching ratios of the MD and TD of the olefin resin film 20 are within the above ranges, it becomes easier to obtain the strength, heat resistance, and barrier properties of the olefin resin film 20.

[0033] The surface layer 31 may further contain a compatibilizer. Since the polypropylene resin constituting the surface layer 31 generally does not have functional groups, it tends to have poor adhesion to the metal oxide particles 32. Therefore, when stretching is performed with the metal oxide particles 32 present, the interface between the polypropylene resin and the metal oxide particles 32 may peel off, creating voids. When voids occur, the metal oxide particles 32 may detach during or after stretching, and defects may form in the transparent vapor-deposited layer 40 at the detached areas, resulting in a decrease in the barrier properties of the laminated film 10.

[0034] As a compatibilizer, one having a polyolefin backbone and containing an acid anhydride in its side chains is preferably used. In particular, an acid anhydride with a polypropylene backbone is preferred. When an acid anhydride is used as a compatibilizer, the acid anhydride bonds with the hydroxyl groups of the metal oxide, etc., and the adhesion between the polypropylene resin and the metal oxide particles 32 is increased. As a result, it is possible to prevent delamination at the interface between the resin and the metal oxide particles 32 caused by stretching, and defects in the transparent vapor-deposited layer 40 can be suppressed.

[0035] The concentration of the compatibilizer is not particularly limited, but it is preferably 0.1 wt% or more and less than 20 wt%, more preferably 0.5 wt% or more and less than 15 wt%, and even more preferably 1.0 wt% or more and less than 10 wt%, relative to the total mass of the surface layer 31 containing the metal oxide particles 32. If the concentration of the compatibilizer is less than 0.1 wt%, the amount of functional groups of the compatibilizer relative to the metal oxide particles 32 becomes relatively small, and the effect of improving adhesion tends to be small. On the other hand, if the concentration of the compatibilizer is 20 wt% or more, there is an excess amount of compatibilizer relative to the metal oxide particles 32, which not only increases the possibility of performance degradation but is also undesirable from an economic standpoint.

[0036] The core layer 30 and surface layer 31 constituting the olefin resin film 20 may contain various additives, to the extent that they do not impair the properties of the laminated film 10 according to this embodiment. Examples of such additives include antiblocking agents, crosslinking agents, nucleating agents, fillers, reinforcing agents, slip agents, lubricants, plasticizers, antioxidants, heat stabilizers, weathering agents, light stabilizers, ultraviolet absorbers, antistatic agents, flame retardants, flame retardant enhancers, antifogging agents, pigments, dyes, dispersants, neutralizing agents, natural oils, synthetic oils, waxes, and modifying resins. In this embodiment, two or more of these may be used in combination.

[0037] The transparent vapor-deposited layer 40 is a layer laminated in direct contact with the olefin resin film 20. The transparent vapor-deposited layer 40 can be formed by conventionally known methods, for example, by physical vapor deposition (PVD) methods such as vacuum deposition, sputtering, and ion plating, or by chemical vapor deposition (CVD) methods such as plasma chemical vapor deposition, thermochemical vapor deposition, and photochemical vapor deposition.

[0038] The materials constituting the transparent vapor-deposited layer 40 include inorganic oxides such as aluminum oxide, silicon oxide, magnesium oxide, calcium oxide, zirconium oxide, titanium oxide, boron oxide, hafnium oxide, and barium oxide. In particular, aluminum oxide or silicon oxide are preferred because they have excellent productivity and excellent heat resistance, heat resistance, and oxygen and water vapor barrier properties. The transparent vapor-deposited layer 40 may be formed from one type of material, or from two or more materials selected as appropriate. The thickness of the transparent vapor-deposited layer 40 may be in the range of 0.001 μm to 0.2 μm, and preferably in the range of 0.005 μm to 0.1 μm. By setting the thickness of the transparent vapor-deposited layer 40 within the above numerical range, sufficient gas barrier properties can be provided while sufficiently minimizing the impact on recyclability, and cracks and other defects are less likely to occur in the transparent vapor-deposited layer 40.

[0039] Figure 3 is a schematic cross-sectional view showing another example of the laminated film 10 of this embodiment. In the laminated film 10 shown in Figure 3, the surface layer 31 and the transparent vapor deposition layer 40 constituting the olefin resin film 20 are laminated in direct contact without an anchor coat layer or adhesive. A seal layer 33 is laminated on the surface of the olefin resin film 20 opposite to the transparent vapor deposition layer 40.

[0040] As the constituent resin of the seal layer 33, olefin resins such as low-density polyethylene, linear low-density polyethylene, high-density polyethylene, homopolypropylene, block polypropylene, random polypropylene, ethylene-vinyl alcohol copolymer, cyclic olefin copolymer, and blends of two or more of these can be used. Preferably, homopolypropylene, block polypropylene, or random polypropylene of the same type as the resin of the surface layer 31 is used. Using the same type of polypropylene significantly improves recyclability. Even more preferably, random polypropylene of the same type as the surface layer 31 is used. The use of random polypropylene for both the surface layer 31 and the seal layer 33 is expected to suppress curling during molding. Furthermore, when the seal layer 33 is used to form a packaging material described later, it will be laminated with another substrate or sealant via an adhesive resin layer, etc., and in this case, it has a lower melting point compared to homopolypropylene, etc., so it has good thermal adhesion and is therefore preferably used.

[0041] In the sealing layer 33, various additives may be mixed in, to the extent that they do not impair the properties of the laminated film 10 according to this embodiment. Examples of various additives include antiblocking agents, crosslinking agents, nucleating agents, fillers, reinforcing agents, slip agents, lubricants, plasticizers, antioxidants, heat stabilizers, weathering agents, light stabilizers, ultraviolet absorbers, antistatic agents, flame retardants, flame retardant enhancers, antifogging agents, pigments, dyes, dispersants, neutralizing agents, natural oils, synthetic oils, waxes, and modifying resins. In this embodiment, two or more of these may be used in combination.

[0042] <Method for manufacturing laminated film 10> The laminated film 10 of this embodiment is formed by laminating an olefin resin film 20 and a transparent vapor-deposited layer 40 without using an anchor coat layer or adhesive. Methods for forming the olefin resin film 20 include blending metal oxide particles 32 and a compatibilizer with the resin forming the surface layer 31, and forming a masterbatch using a kneader or twin-screw extruder. Methods include laminating this masterbatch and the resin forming the core layer 30 by co-extrusion to form a film, or pouring the molten masterbatch onto the core layer 30 melted on a hot plate to laminate the surface layer 31. From the viewpoint of manufacturing cost, it may also be manufactured roll-to-roll by co-extrusion. By manufacturing in this way, the manufacturing process can be simplified, the inclusion of impurities can be prevented, and recyclability can be improved.

[0043] The resin, which is molten and laminated from a T-die by co-extrusion, is cooled and solidified into a film by multiple cooling rolls. The molten resin can be fixed to the cooling rolls by known methods. For example, there are methods such as pressing it against the cooling rolls with a nip roll, pressing it against the cooling rolls with air such as an air knife or air chamber, pressing it against the cooling rolls electrically such as electrostatic pinning, and taking it up by applying tension without pressing it. In this embodiment, from the viewpoint of uniformity of performance, productivity, and safety, the method of pressing it against the cooling rolls with air such as an air knife or air chamber is more preferable.

[0044] Furthermore, if the laminated film 10 includes a sealing layer 33, methods include laminating a masterbatch for forming the surface layer 31, a resin for forming the core layer 30, and a resin for forming the sealing layer 33 by co-extrusion to form a film, or pouring a molten resin composition for forming the core layer 30 onto a molten sealing layer 33 on a hot plate to laminate the core layer 30, and then pouring a molten masterbatch onto the laminated core layer 30 to laminate the surface layer 31. The above methods can be used for film formation.

[0045] The olefin resin film 20 is formed into a film as described above and then stretched. From the viewpoint of strength and productivity, the stretching may be sequential biaxial stretching. The stretching temperature should be above the softening point of each laminated resin and below the melting point of the resin of the core layer 30. By stretching in this temperature range, the olefin resin film 20 is suitably stretched and oriented, making it possible to improve its strength and heat resistance. The transparent vapor-deposited layer 40 is laminated so as to be in direct contact with the surface layer 31 of the olefin resin film 20 prepared as described above. Before laminating the transparent vapor-deposited layer 40, the surface of the surface layer 31 can also be subjected to surface treatment such as corona treatment or plasma treatment. By performing surface treatment, it becomes possible to produce a laminated film 10 with improved adhesion between the olefin resin film 20 and the transparent vapor-deposited layer 40.

[0046] <Packaging material 100> The laminated film 10 of this embodiment can be used as a packaging material 100 by further laminating a coating layer 50 and a heat seal layer 60 made of a barrier material onto it. Specifically, a coating layer 50 made of a barrier material can be laminated on top of the transparent vapor-deposited layer 40, and a heat seal layer 60 can be further laminated on the side of the olefin resin film 20 opposite to the transparent vapor-deposited layer 40.

[0047] <Coating layer 50> The coating layer 50, which is composed of a barrier material, may contain, as constituent materials, at least one of a metal alkoxide, its hydrolysate, and its reaction product, and a film-forming agent, and may further contain at least one of a silane coupling agent and its hydrolysate.

[0048] Examples of metal alkoxides and their hydrolysates include tetraethoxysilane [Si(OC2H5)4] and triisopropoxyaluminum [Al(OC3H7)3], which have the general formula M(OR). n Examples include substances represented by [the formula], and their hydrolysates. In this embodiment, only one of these may be included, or two or more may be included in appropriate combinations. For example, a water-soluble polymer can be used as the film-forming agent. Examples of water-soluble polymers include polyvinyl alcohol-based polymers, polysaccharides such as starch, methylcellulose, and carboxymethylcellulose, and various polymers such as acrylic polyol-based polymers. From the viewpoint of further improving oxygen gas barrier properties, the coating layer 50 may contain a polyvinyl alcohol-based polymer as the film-forming agent.

[0049] The coating layer 50, composed of a barrier material, can be formed by conventionally known methods, such as the casting method, dipping method, roll coating method, gravure coating method, screen printing method, reverse coating method, spray coating method, kit coating method, die coating method, metering bar coating method, chamber doctor combined coating method, curtain coating method, and other wet coating methods. The film thickness of the coating layer 50, which is composed of a barrier material, may be in the range of 0.05 μm to 1 μm, and preferably in the range of 0.1 μm to 0.5 μm. By setting the film thickness of the coating layer 50 within the above numerical range, sufficient oxygen barrier properties can be provided while sufficiently minimizing the impact on recyclability, making it easy to form a uniform coated surface and suppressing drying load and manufacturing costs.

[0050] <Heat seal layer 60> The material constituting the heat seal layer 60 is, for example, a polyolefin resin of the same type as the olefin resin film 20. The heat seal layer 60 may contain the above-mentioned polyethylene resin as the constituent resin of the olefin resin film 20, and may contain multiple polyethylene resins with different melting points, MFRs, etc. The olefin resin film 20 may contain the above-mentioned polypropylene resin as the constituent resin, and may contain multiple polypropylene resins with different melting points, MFRs, etc. The heat seal layer 60 may contain, from the viewpoint of low-temperature heat sealability and flexibility, a polypropylene resin copolymerized with random polypropylene or α-olefin as the polypropylene resin, and may also contain linear low-density polyethylene (LLDPE) copolymerized with α-olefin and ethylene as the polyethylene resin.

[0051] The melting point of the heat seal layer 60 is preferably lower than the melting point of the olefin resin film 20. Here, the melting point refers to the average melting point obtained from the melting points of each component of the resin contained in the heat seal layer 60 and their composition ratio (mass ratio). The difference in melting points between the heat seal layer 60 and the olefin resin film 20 may be 5°C or more, preferably 10°C or more, more preferably 15°C or more, even more preferably 20°C or more, or most preferably 25°C or more. By keeping the difference in melting points between the heat seal layer 60 and the olefin resin film 20 within the above range, shrinkage and wrinkling due to heat during heat sealing can be prevented.

[0052] Furthermore, the melting point of the heat seal layer 60 may be 120°C or higher, preferably 130°C or higher, or more preferably 135°C or higher, when the constituent resin of the heat seal layer 60 is polypropylene resin. Alternatively, the melting point of the heat seal layer 60 may be 165°C or lower, preferably 150°C or lower, or more preferably 140°C or lower. The lower the melting point of the heat seal layer 60, the more sufficient heat sealability can be obtained even at low temperatures. As such a polypropylene resin, random polypropylene is preferred, and it is preferred that it be the main component of the heat seal layer 60. In this embodiment, the term "main component" refers to a resin component that makes up 50% by mass or more of the total mass of the resin components constituting the heat seal layer 60. In other words, in this embodiment, it is preferable that the mass of random polypropylene is 50% by mass or more of the total mass of the resin components constituting the heat seal layer 60, more preferably 80% by mass or more, even more preferably 90% by mass or more, and most preferably 100% by mass.

[0053] When the heat seal layer 60 is formed by including two or more types of resin, it may include a component with a high melting point (high-melting point component) and a component with a low melting point (low-melting point component). The high-melting point component may be a component with a melting point of 155°C or higher and less than 165°C, and the low-melting point component may be a component with a melting point of 120°C or higher and less than 150°C. By including a high-melting point component and a low-melting point component in the heat seal layer 60, it becomes easier to prevent the heat seal layers 60 from adhering to each other in unintended areas while ensuring adhesive strength during heat sealing. Furthermore, by including a high-melting point component and a low-melting point component in the heat seal layer 60, resistance to retort processing can be improved, thereby enhancing the retort suitability of the packaging material 100.

[0054] When the heat seal layer 60 is formed by including two or more types of resin, the content of the low-melting-point component may be in the range of 20 parts by mass or more and 80 parts by mass or less, with the total mass of the high-melting-point component and the low-melting-point component being 100 parts by mass, preferably in the range of 30 parts by mass or more and 70 parts by mass or less, and more preferably in the range of 40 parts by mass or more and 60 parts by mass or less. A content of 20 parts by mass or more of the low-melting-point resin component (low-melting-point component) makes it easier to obtain heat sealability. Furthermore, a content of 80 parts by mass or less of the low-melting-point resin component (low-melting-point component) makes it easier to prevent the heat seal layers 60 from adhering to each other in unintended areas while ensuring adhesive strength during heat sealing. Furthermore, from the viewpoint of heat sealability performance alone, the content of the low-melting-point component may be in the range of 30 parts by mass or more and 80 parts by mass or less, with the total mass of the high-melting-point component and the low-melting-point component being 100 parts by mass, preferably in the range of 40 parts by mass or more and 80 parts by mass or less, and more preferably in the range of 50 parts by mass or more and 80 parts by mass or less.

[0055] The heat seal layer 60 may contain various additives, to the extent that they do not impair the properties of the packaging material 100 according to this embodiment. Examples of such additives include antiblocking agents, crosslinking agents, nucleating agents, fillers, reinforcing agents, slip agents, lubricants, plasticizers, antioxidants, heat stabilizers, weathering agents, light stabilizers, ultraviolet absorbers, antistatic agents, flame retardants, flame retardant enhancers, antifogging agents, pigments, dyes, dispersants, neutralizing agents, natural oils, synthetic oils, waxes, and modifying resins. In this embodiment, two or more of these may be used in combination. The thickness of the heat seal layer 60 may be within the range of 10 μm to 150 μm, preferably within the range of 20 μm to 120 μm, and more preferably within the range of 30 μm to 100 μm. By having the thickness of the heat seal layer 60 within the above range, the strength of the packaging material 100 and the heat seal strength during heat sealing can be improved.

[0056] The olefin resin film 20 and the heat seal layer 60 are bonded together without the use of an adhesive. This improves recyclability. Methods for bonding the olefin resin film 20 and the heat seal layer 60 include a direct heat-sealing method by extrusion lamination, where the heat seal layer 60 is laminated to the extruded olefin resin film 20 as a base material; a method of co-extruding the heat seal layer 60 and an adhesive resin, and then extruding laminating the olefin resin film 20 onto the adhesive resin surface formed on the heat seal layer 60; and a method of separately forming the olefin resin film 20 and the heat seal layer 60 into films and then heat-bonding them by heat lamination. For a stronger bond and lower manufacturing cost, the method of co-extruding the heat seal layer 60 and an adhesive resin, and then extruding laminating the olefin resin film 20 onto the adhesive resin surface formed on the heat seal layer 60 is preferred. In this embodiment, the adhesive resin is preferably a resin that has a backbone of the same type of resin as the olefin resin film 20 and the heat seal layer 60, and has functional groups such as acid anhydrides in its side chains. Furthermore, the "adhesive resin" mentioned above is different from commonly used urethane-based adhesives.

[0057] The packaging material 100 of this embodiment can also be further laminated with other base materials or functional layers. This makes it possible to improve heat resistance, strength, and impart other functions. The packaging material 100 of this embodiment can be used to manufacture a packaging bag by folding it in half so that the heat-seal layer 60 is on the inside, overlapping the two halves, and then heat-sealing the edges. Alternatively, the packaging material 100 can also be manufactured by overlapping two pieces of packaging material so that the heat-seal layers 60 face each other, and then heat-sealing the edges. Examples of heat sealing methods include side-seal type, two-side-seal type, three-side-seal type, four-side-seal type, envelope-type seal, gusset-type seal (pillow seal type), pleated seal type, flat-bottom seal type, square-bottom seal type, and gusset type. By selecting these appropriately, various types of packaging bags can be manufactured.

[0058] According to the packaging material 100 of this embodiment, for example, self-standing packaging bags (standing pouches) can also be manufactured. The method of manufacturing the self-standing packaging bags is not particularly limited. As for the heat sealing method, known methods such as bar sealing, rotary roll sealing, belt sealing, impulse sealing, high-frequency sealing, and ultrasonic sealing can be used. According to the packaging material 100 of this embodiment, by incorporating the laminated film 10 of this embodiment, it is possible to produce a package with high recyclability. Furthermore, according to the packaging material 100 of this embodiment, by incorporating the laminated film 10 of this embodiment, it is possible to produce a package suitable for retort packaging.

[0059] [Examples] The present inventors will now describe in detail the embodiments they have created in comparison with comparative examples, but the present invention is not limited to the embodiments described below.

[0060] (Example 1) Random polypropylene (random PP) resin F-794NV (manufactured by Prime Polymer Co., Ltd.) was used as the constituent resin for the surface layer 31, and alumina AA-03F (manufactured by Sumitomo Chemical Co., Ltd.; primary particle size 260 nm) was used as the metal oxide particles 32. These were kneaded in a twin-screw extruder to prepare a masterbatch with an alumina concentration of 30 wt%. The resin temperature during twin-screw extrusion was 160°C. Subsequently, a two-layer olefin resin film 20 was produced by co-extruding homopolypropylene (homoPP) resin F-300SP (manufactured by Prime Polymer Co., Ltd.), which is the constituent resin of the core layer 30, and the above masterbatch with an alumina concentration of 30 wt%, which is the constituent material of the surface layer 31. The resin temperature during uniscrew extrusion was 250°C. The thickness of the core layer 30 was 45 μm, and the thickness of the surface layer 31 was 5 μm. A laminated film 10 was fabricated by vacuum-depositing silicon dioxide (SiOx) onto the surface layer 31 of the olefin resin film 20 prepared as described above, thereby forming a transparent vapor-deposited layer 40 made of inorganic oxide. The thickness of the transparent vapor-deposited layer 40 was 30 nm. Furthermore, the amount of metal oxide particles 32 exposed from the surface layer 31 (Al / C) in Example 1 was 0.0029.

[0061] (Example 2) Homopolypropylene resin F-300SP was used as the constituent resin for the surface layer 31, and alumina AA-03F was used as the metal oxide particles 32. These were kneaded in a twin-screw extruder to prepare a masterbatch with an alumina concentration of 30 wt%. From thereafter, the laminated film 10 was fabricated using the same method as in Example 1. The thickness of the core layer 30 was 45 μm, the thickness of the surface layer 31 was 5 μm, and the thickness of the transparent vapor-deposited layer 40 was 30 nm. Furthermore, the amount of metal oxide particles 32 exposed from the surface layer 31 (Al / C) in Example 2 was 0.0027.

[0062] (Example 3) Random polypropylene resin F-794NV was used as the constituent resin for the surface layer 31, and alumina AA-03F was used as the metal oxide particles 32. These were kneaded in a twin-screw extruder to prepare a masterbatch with an alumina concentration of 30 wt%. The resin temperature during twin-screw extrusion was 160°C. Subsequently, a two-layer olefin resin film 20 was fabricated by co-extrusion molding of homopolypropylene resin F-300SP, which is the constituent resin of the core layer 30, and a material obtained by diluting the above masterbatch with random polypropylene resin F-794NV and adjusting the alumina concentration to 15 wt%, which is the constituent material of the surface layer 31. The resin temperature during uniscrew extrusion was 250°C. The thickness of the core layer 30 was 45 μm, and the thickness of the surface layer 31 was 5 μm. A laminated film 10 was fabricated by vacuum-depositing silicon oxide onto the surface layer 31 of the olefin resin film 20 prepared as described above, thereby forming a transparent vapor-deposited layer 40 made of inorganic oxide. The thickness of the transparent vapor-deposited layer 40 was 30 nm. Furthermore, the amount of metal oxide particles 32 exposed from the surface layer 31 (Al / C) in Example 3 was 0.0014.

[0063] (Example 4) A laminated film 10 was fabricated by plasma treatment under an argon atmosphere on the surface layer 31 of the olefin resin film 20 prepared in Example 1, followed by vacuum deposition of silicon oxide to form a transparent deposition layer 40 made of inorganic oxide. The thickness of the core layer 30 was 45 μm, the thickness of the surface layer 31 was 5 μm, and the thickness of the transparent deposition layer 40 was 30 nm. Furthermore, the amount of metal oxide particles 32 exposed from the surface layer 31 (Al / C) in Example 4 was 0.0033.

[0064] (Example 5) Random polypropylene resin F-724NPC (manufactured by Prime Polymer Co., Ltd.) was used as the constituent resin for the surface layer 31, and alumina AA-03F was used as the metal oxide particles 32. These were kneaded in a twin-screw extruder to prepare a masterbatch with an alumina concentration of 30 wt%. The resin temperature during twin-screw extrusion was 160°C. Subsequently, a two-layer olefin resin sheet was produced by co-extruding the homopolypropylene resin F-300SP (manufactured by Prime Polymer Co., Ltd.), which is the constituent resin of the core layer 30, with the above masterbatch containing 30 wt% alumina, which is the constituent material of the surface layer 31. The resin temperature during uniscrew extrusion was 250°C. The thickness of the core layer 30 was 630 μm, and the thickness of the surface layer was 17.5 μm. A biaxially oriented olefin resin film 20 was produced by biaxial stretching the fabricated olefin resin sheet at a magnification of 5x MD and 7x TD. The thickness of the core layer 30 was 18 μm, and the thickness of the surface layer 31 was 0.5 μm. A laminated film 10 was fabricated by vacuum-depositing silicon oxide onto the surface layer 31 of the biaxially stretched olefin resin film 20 prepared as described above, thereby forming a transparent vapor-deposited layer 40 made of inorganic oxide. The thickness of the transparent vapor-deposited layer 40 was 30 nm. Furthermore, the amount of metal oxide particles 32 exposed from the surface layer 31 (Al / C) in Example 5 was 0.025.

[0065] (Example 6) Random polypropylene resin F-724NPC (manufactured by Prime Polymer Co., Ltd.) was used as the constituent resin for the surface layer 31, alumina AA-03F (manufactured by Sumitomo Chemical Co., Ltd.; primary particle size 260 nm) was used as the metal oxide particles 32, and MG-250P (manufactured by Riken Vitamin Co., Ltd.) was used as the compatibilizer. These were kneaded in a twin-screw extruder to prepare a masterbatch with an alumina concentration of 30 wt% and a compatibilizer concentration of 5 wt%. The resin temperature during twin-screw extrusion was 160°C. From thereafter, the laminated film 10 was fabricated using the same method as in Example 5. The thickness of the core layer 30 was 18 μm, the thickness of the surface layer 31 was 0.5 μm, and the thickness of the transparent vapor-deposited layer 40 was 30 nm. Furthermore, the amount of metal oxide particles 32 exposed from the surface layer 31 (Al / C) in Example 6 was 0.027.

[0066] (Example 7) A laminated film 10 was fabricated by plasma treatment under an argon atmosphere on the surface layer 31 of the biaxially stretched olefin resin film 20 prepared in Example 5, followed by vacuum deposition of silicon oxide to form a transparent deposition layer 40 made of inorganic oxide. The thickness of the core layer 30 was 18 μm, the thickness of the surface layer 31 was 0.5 μm, and the thickness of the transparent deposition layer 40 was 30 nm. Furthermore, the amount of metal oxide particles 32 exposed from the surface layer 31 (Al / C) in Example 7 was 0.028.

[0067] (Example 8) A laminated film 10 was fabricated by plasma treatment under an argon atmosphere on the surface layer 31 of the biaxially stretched olefin resin film 20 prepared in Example 6, followed by vacuum deposition of silicon oxide to form a transparent deposition layer 40 made of inorganic oxide. The thickness of the core layer 30 was 18 μm, the thickness of the surface layer 31 was 0.5 μm, and the thickness of the transparent deposition layer 40 was 30 nm. Furthermore, the amount of metal oxide particles 32 exposed from the surface layer 31 (Al / C) in Example 8 was 0.028.

[0068] (Example 9) Random polypropylene resin F-724NPC (manufactured by Prime Polymer Co., Ltd.) was used as the constituent resin for the surface layer 31, alumina AA-03F (manufactured by Sumitomo Chemical Co., Ltd.; primary particle size 260 nm) was used as the metal oxide particles 32, and MG-250P (manufactured by Riken Vitamin Co., Ltd.) was used as the compatibilizer. These were kneaded in a twin-screw extruder to prepare a masterbatch with an alumina concentration of 30 wt% and a compatibilizer concentration of 10 wt%. The resin temperature during twin-screw extrusion was 160°C. Subsequently, a two-layer olefin resin sheet was produced by co-extruding the homopolypropylene resin F-300SP (manufactured by Prime Polymer Co., Ltd.), which is the constituent resin of the core layer 30, with the above masterbatch, which is the constituent material of the surface layer 31, having an alumina concentration of 30 wt% and a compatibilizer concentration of 10 wt%. The resin temperature during uniscrew extrusion was 250°C. The thickness of the core layer 30 was 630 μm, and the thickness of the surface layer 31 was 17.5 μm. A biaxially oriented olefin resin film 20 was produced by biaxial stretching the fabricated olefin resin sheet at a magnification of 5x MD and 7x TD. The thickness of the core layer 30 was 18 μm, and the thickness of the surface layer 31 was 0.5 μm. A laminated film 10 was fabricated by plasma treatment under an argon atmosphere on the surface layer 31 of the biaxially stretched olefin resin film 20 prepared as described above, followed by vacuum deposition of silicon oxide to form a transparent deposition layer 40 made of inorganic oxide. The thickness of the core layer 30 was 18 μm, the thickness of the surface layer 31 was 0.5 μm, and the thickness of the transparent deposition layer 40 was 30 nm. Furthermore, the amount of metal oxide particles 32 exposed from the surface layer 31 (Al / C) in Example 9 was 0.029.

[0069] (Example 10) Random polypropylene resin F-794NV (manufactured by Prime Polymer Co., Ltd.) was used as the constituent resin for the surface layer 31, alumina AA-03F (manufactured by Sumitomo Chemical Co., Ltd.; primary particle size 260 nm) was used as the metal oxide particles 32, and MG-250P (manufactured by Riken Vitamin Co., Ltd.) was used as the compatibilizer. These were kneaded in a twin-screw extruder to prepare a masterbatch with an alumina concentration of 30 wt% and a compatibilizer concentration of 10 wt%. The resin temperature during twin-screw extrusion was 160°C. From thereafter, the laminated film 10 was fabricated using the same method as in Example 9. The thickness of the core layer 30 was 18 μm, the thickness of the surface layer 31 was 0.5 μm, and the thickness of the transparent vapor-deposited layer 40 was 30 nm. Furthermore, the amount of metal oxide particles 32 exposed from the surface layer 31 (Al / C) in Example 10 was 0.029.

[0070] (Comparative Example 1) A two-layer olefin resin sheet was fabricated by co-extruding a random polypropylene resin F-724NPC (manufactured by Prime Polymer Co., Ltd.), which is the constituent resin of the surface layer 31, and a homopolypropylene resin F-300SP (manufactured by Prime Polymer Co., Ltd.), which is the constituent resin of the core layer 30. The resin temperature during uniscrew extrusion was 250°C. The thickness of the core layer 30 was 630 μm, and the thickness of the surface layer 31 was 17.5 μm. A biaxially oriented olefin resin film 20 was produced by biaxial stretching the fabricated olefin resin sheet at a magnification of 5x MD and 7x TD. The thickness of the core layer 30 was 18 μm, and the thickness of the surface layer 31 was 0.5 μm. A laminated film 10 was fabricated by vacuum-depositing silicon oxide onto the surface layer 31 of the olefin resin film 20 prepared as described above, thereby forming a transparent vapor-deposited layer 40 made of inorganic oxide. The thickness of the transparent vapor-deposited layer 40 was 30 nm. Furthermore, the amount of metal oxide particles 32 exposed from the surface layer 31 (Al / C) in Comparative Example 1 was 0.

[0071] [Amount of exposed metal oxide particles] The amount of metal oxide particles 32 exposed from the surface layer 31 of the olefin resin film 20 was determined. Narrow scan analysis was performed using an X-ray photoelectron spectroscopy analyzer (ULVAC-PHI, Quantum2000) to calculate the ratio of carbon atoms to aluminum atoms (Al / C). Specifically, the ratio of carbon atoms to aluminum atoms (Al / C) was calculated from the peak area due to aluminum atoms and the peak area due to carbon atoms. Furthermore, if the ratio of carbon atoms to aluminum atoms (Al / C) is 0.001 or greater, at least a portion of the surface of the metal oxide particles 32 is exposed from the surface layer 31.

[0072] [Oxygen permeability measurement] Oxygen permeability was measured for laminated film 10. The measurement was performed using a gas permeability measuring device (Toyo Rika Co., Ltd., K-315-N) under conditions of 30°C and 0% relative humidity. The measurement method conformed to JIS K-7126-1 (differential pressure method) and ASTM D 1434M method. For the oxygen permeability measurement evaluation, compared to the oxygen permeability (reference value) of the laminated film 10 of Comparative Example 1 (corresponding to the conventional laminated film) in which metal oxide particles 32 were not added to the surface layer 31, those with an 80% or greater decrease in oxygen permeability and excellent oxygen barrier properties were marked "◎", those with an 50% to less than 80% decrease in oxygen permeability and improved oxygen barrier properties were marked "〇", and those with a 20% to less than 50% decrease in oxygen permeability and improved oxygen barrier properties were marked "△". In this example, a rating of "◎", "〇", or "△" was considered a "pass".

[0073] [Recyclability] Recyclability was evaluated based on whether or not anchor layers or adhesives were used to join each layer. A "○" rating indicated that anchor layers or adhesives were not used to join the layers. In this example, a rating of "〇" was considered a "pass".

[0074] Table 1 shows the film configurations and evaluation results for Examples 1 to 10 and Comparative Example 1.

[0075] [Table 1]

[0076] (Evaluation results) As shown in Table 1, it was confirmed that the oxygen barrier properties were improved by exposing a portion of the surface of the metal oxide particles 32 on the surface layer 31 of the olefin resin film 20. Comparisons between Example 1 and Example 4, between Example 5 and Example 7, and between Example 6 and Example 8 confirmed that the oxygen barrier properties were improved by performing plasma treatment. Furthermore, from the results of Examples 7 to 10, it was confirmed that the barrier improvement effect was enhanced by adding a compatibilizer to the stretched olefin resin film 20.

[0077] Furthermore, for example, this embodiment can take the following configuration. (1) The olefin resin film comprises a transparent vapor-deposited layer laminated in direct contact with the olefin resin film, The olefin resin film comprises at least a core layer and a surface layer in this order. The transparent vapor deposition layer and the surface layer are adjacent to each other. The aforementioned surface layer contains metal oxide particles, A laminated film characterized in that a portion of the surface of the metal oxide particles is exposed from the surface layer. (2) The core layer is mainly composed of homopolypropylene, The laminated film according to (1) above, characterized in that the surface layer is mainly composed of random polypropylene. (3) The laminated film according to (1) or (2) above, characterized in that the olefin resin film is a biaxially oriented film. (4) The laminated film according to any one of (1) to (3) above, characterized in that the surface layer further contains a compatibilizer. (5) A laminated film as described in any one of the above items (1) to (4), A coating layer formed of a barrier material is laminated on the transparent vapor-deposited layer, A packaging material characterized by comprising a heat-seal layer mainly composed of random polypropylene on the side of the olefin resin film opposite to the transparent vapor-deposited layer. (6) A method for manufacturing a laminated film as described in any one of the above items (1) to (4), A step of forming the olefin resin film such that the metal oxide particles are exposed from the surface layer, After forming the olefin resin film, the process involves performing plasma treatment on the surface of the surface layer, A method for manufacturing a laminated film, characterized by having a step of forming the transparent vapor deposition layer after performing the plasma treatment. [Explanation of symbols]

[0078] 10...Laminated film, 20...Olefin resin film, 30...Core layer, 31...Surface layer, 32...Metal oxide particles, 33...Seal layer, 40...Transparent vapor deposition layer, 50...Coating layer, 60...Heat seal layer, 100...Packaging material

Claims

1. The olefin resin film comprises a transparent vapor-deposited layer laminated in direct contact with the olefin resin film, The olefin resin film comprises at least a core layer and a surface layer in this order. The transparent vapor deposition layer and the surface layer are adjacent to each other. The aforementioned surface layer contains metal oxide particles, A laminated film characterized in that a portion of the surface of the metal oxide particles is exposed from the surface layer.

2. The core layer is mainly composed of homopolypropylene, The laminated film according to claim 1, characterized in that the surface layer is mainly composed of random polypropylene.

3. The laminated film according to claim 1, characterized in that the olefin resin film is a biaxially oriented film.

4. The laminated film according to claim 1, characterized in that the surface layer further contains a compatibilizer.

5. A laminated film according to any one of claims 1 to 4, A coating layer formed of a barrier material is laminated on the transparent vapor-deposited layer, A packaging material characterized by comprising a heat-seal layer mainly composed of random polypropylene on the side of the olefin resin film opposite to the transparent vapor-deposited layer.

6. A method for manufacturing a laminated film according to any one of claims 1 to 4, A step of forming the olefin resin film such that the metal oxide particles are exposed from the surface layer, After forming the olefin resin film, the process involves performing plasma treatment on the surface of the surface layer, A method for manufacturing a laminated film, characterized by having a step of forming the transparent vapor deposition layer after performing the plasma treatment.

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