Packaging films and packages

Abstract

To provide a packaging film having improved blocking resistance, which has been a defect in a film consisting of a single polyethylene layer, and a package composed of the packaging film.SOLUTION: A packaging film has a base material layer including polyethylene, and a coating layer including a resin different from polyethylene, provided in contact with one side of the base material layer or provided via an anchor coating layer. The whole or part of one side of the coating layer is an exposed surface, and the coating layer is 0.3-4.5 μm in thickness.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a packaging film and a package, and more specifically to a packaging film and a package formed by the packaging film. [Background technology]

[0002] In the field of packaging films, attempts to improve various performances by improving the materials used, layer structures, etc. are known.

[0003] As an example, Patent Document 1 describes a laminated film in which two biaxially oriented plastic films, each having a vinylidene chloride copolymer layer on one side, are laminated with the vinylidene chloride copolymer layer faces facing each other and heat-pressed (the adhesive strength of the two films is 10 to 50 gf / 15 mm). Patent Document 1 describes that this laminated film is resistant to abrasion and punctures (pinholes are unlikely to form) and has excellent gas barrier properties.

[0004] As another example, Patent Document 2 describes a multilayer film in which a gas barrier layer formed by applying a dispersion liquid containing an inorganic layered compound and a water-soluble polymer to at least one surface of a base layer made of a thermoplastic resin, an overcoat layer containing a cationic resin and a resin having a hydroxyl group, an adhesive layer, and a sealant layer are laminated in this order. Patent Document 2 describes that this multilayer film has excellent heat sealability and gas barrier properties.

[0005] As yet another example, Patent Document 3 describes a barrier film having a base layer, an inorganic layer, and a polyvinylidene chloride resin layer in this order. When the infrared absorption spectrum of the polyvinylidene chloride resin layer of this barrier film was measured, -1 Absorption peak height A(1070) at wavenumbers near 1046 cm -1The peak ratio (A(1046) / A(1070)) of the absorption peak height A(1046) at a wave number in the vicinity of is 1.3 or less. Patent Document 3 describes that this barrier film has excellent blocking resistance. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 10-337825 [Patent Document 2] JP 2009-241359 A [Patent Document 3] JP 2017-114079 A Summary of the Invention [Problem to be solved by the invention]

[0007] In recent years, with growing environmental awareness, and especially with the focus on the problem of marine plastic pollution, society has been paying closer attention to packaging films. And there is now more demand than ever for the promotion of recycling of packaging films. In other words, there is now a growing demand to design and manufacture packaging films with consideration for "ease of recycling."

[0008] Many of the conventional packaging films have achieved desired effects (such as strength and gas barrier properties) by laminating a variety of materials. For example, the multilayer film described in Patent Document 2 has at least four layers: a gas barrier layer, an overcoat layer, an adhesive layer, and a sealant layer. However, laminating a variety of materials makes it difficult to recycle. From the viewpoint of facilitating recycling of packaging films, for example, it is conceivable to make the packaging film have as simple a layer structure as possible.

[0009] In terms of simplifying the layer structure, it may be possible, in the extreme, to make the packaging film "single layer." The present inventors have conducted a preliminary study on various properties that may be required for packaging films using polyethylene film, which is a relatively low-cost and versatile packaging material. As a result of the study, it was found that a "single-layer" polyethylene film did not exhibit sufficient performance, for example, in terms of blocking resistance.

[0010] An object of the present invention is to provide a packaging film having improved blocking resistance, which is insufficient in a single-layer polyethylene film, and a package made of such a packaging film. [Means for solving the problem]

[0011] The present invention is as follows.

[0012] 1. A base layer including polyethylene; A coating layer containing a resin different from polyethylene and provided in contact with one side of the base layer or provided via an anchor coat layer; Equipped with A part or the whole of one side of the coating layer is an exposed surface, The coating layer of the packaging film has a thickness of 0.3 to 4.5 μm. 2. 1. The packaging film according to claim 1, The thickness of the base layer of the packaging film is 10 to 150 μm. 3. 1. The packaging film according to 1. or 2. A packaging film, wherein the exposed surface has a ten-point average roughness SRz of 0.50 μm or more, as determined by three-dimensional surface measurement. 4. The packaging film according to any one of 1. to 3., A packaging film having a kurtosis (Sku) of 25 or more on the exposed surface, as determined by three-dimensional surface measurement. 5. The packaging film according to any one of 1. to 4., The packaging film, wherein the resin other than polyethylene is at least one selected from the group consisting of polyurethane, polyvinyl alcohol, and polyvinylidene chloride. 6. The packaging film according to any one of 1. to 5., The oxygen permeability measured under the conditions of temperature 23±2℃ and humidity 90±1.0% RH is 1.0×105mL / (m 2 ·day·MPa), and / or the oxygen permeability measured under the conditions of temperature 23±2°C and humidity 50±1.0% RH is 1.0×105mL / (m 2 Packaging film with a thermal conductivity of less than 1.5 MPa. 7. The packaging film according to any one of 1. to 6., A packaging film, wherein when the glass transition temperature of the coating layer is Tgc and the glass transition temperature of the base layer is Tgs, the Tgc value is -25 to 120°C and the Tgc-Tgs value is 90 to 245°C. 8. The packaging film according to any one of 1. to 7., The coating layer is a packaging film having no melting point or a melting point of 120 to 245°C. 9. The packaging film according to any one of 1. to 8., A packaging film in which the coefficient of static friction between the surfaces of the base layer is 0.08 to 2.50 10. The packaging film according to any one of 1. to 9., The coating layer comprises a surfactant, The surface resistivity of the coating layer is 1×10 12 ~1×10 15 Packaging film that is Omega. 11. The packaging film according to any one of 1. to 10., The coating layer comprises a surfactant, A packaging film, wherein the coating layer has a surfactant content of 0.8 to 7.5% by mass. 12. A package made of the packaging film according to any one of 1. to 11. 13. 12. The package according to claim 12, A package having the coating layer on its outer surface. Effect of the Invention

[0013] According to the present invention, there are provided a packaging film having improved blocking resistance, which is insufficient in a single-layer polyethylene film, and a package made of such a packaging film. [Brief description of the drawings]

[0014] [Figure 1] FIG. 2 is a diagram showing a layer structure of a packaging film. [Diagram 2] 1 is a diagram for explaining a manufacturing method of a "hand-held bag". [Diagram 3] FIG. 3 is a schematic diagram showing the state of the portion α in FIG. 2 as viewed from the direction of the arrow shown in the figure (when the two-sided bag is made of a single-layer film). [Figure 4] This is a schematic diagram showing the state of the part α in FIG. 2 as viewed from the direction of the arrow shown in the figure (when the two-layered bag is made of a film). [Diagram 5] FIG. 2 is a diagram showing a schematic layer structure of a packaging film different from that shown in FIG. 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In all drawings, similar components are given similar symbols and descriptions thereof are omitted where appropriate. In order to avoid complexity, (i) when there are multiple identical components in the same drawing, only one of them will be given a symbol, and not all of them, or (ii) especially in Figure 2 and subsequent figures, components similar to those in Figure 1 will not be given a symbol again. All drawings are for illustrative purposes only. The shapes and dimensional ratios of each component in the drawings do not necessarily correspond to the actual objects.

[0016] In this specification, unless otherwise specified, the expression "X to Y" in the explanation of a numerical range means from X to Y. For example, "1 to 5% by mass" means "from 1% by mass to 5% by mass". In the description of groups (atomic groups) in this specification, when a description is made without specifying whether the group is substituted or unsubstituted, the description includes both groups having no substituents and groups having a substituent. For example, an "alkyl group" includes not only an alkyl group having no substituents (unsubstituted alkyl group) but also an alkyl group having a substituent (substituted alkyl group). In this specification, the term "(meth)acrylic" refers to a concept that includes both acrylic and methacrylic. The same applies to similar terms such as "(meth)acrylate."

[0017] <Packaging film> FIG. 1 is a diagram showing a typical layer structure of the packaging film of the present embodiment. A base layer containing polyethylene (hereinafter also referred to as base layer 1A), A coating layer (hereinafter also referred to as coating layer 1B) containing a resin other than polyethylene and provided in contact with one side of the base layer or provided via an anchor coat layer; Equipped with. In the packaging film of Fig. 1, the coating layer 1B is provided in contact with one surface of the base layer 1A. In other words, the anchor coat layer is not shown in Fig. 1.

[0018] One side of the coating layer 1B (typically the side opposite to the base layer 1A) is partially or entirely exposed, that is, the one side of the coating layer 1B is in contact with the outside air and can be touched. The coating layer 1B has a thickness of 0.3 to 4.5 μm.

[0019] In order to improve the blocking resistance, which is insufficient in a single-layer polyethylene film, the packaging film of this embodiment has a coating layer having a thickness of 0.3 to 4.5 μm, which contains a resin different from polyethylene, provided on one side of the polyethylene film directly or via an anchor coat layer. One way to improve blocking resistance is to provide the surface of the packaging film with microscopic irregularities, which is believed to reduce the contact area between films and improve blocking resistance. Although the details are unclear, it is believed that by providing a relatively thin coating layer with a thickness of 0.3 to 4.5 μm on one side of the base layer 1A, either directly or via an anchor coat layer, appropriate unevenness is provided on the exposed surface of the coating layer 1B. It is believed that the unevenness enhances blocking resistance. In other words, it is believed that the adhesion between films is suppressed when the films are stacked on top of each other or wound into a roll.

[0020] It is presumed that when coating layer 1B is thin, coating layer 1B does not "completely fill" the unevenness of the surface of base material layer 1A, so that the exposed surface of coating layer 1B (the surface opposite base material layer 1A) becomes moderately "rough." In other words, when coating layer 1B is moderately thin, it can be said that coating layer 1B "remains moderately" the unevenness of the surface of base material layer 1A. And / or, when forming coating layer 1B by coating, if the amount of coating liquid applied is small, the volatile components evaporate before the applied coating liquid is sufficiently leveled, i.e., flattened, and therefore, it is presumed that microscopic irregularities are formed on the exposed surface of the coating layer 1B that is formed. Incidentally, as an experimental fact, when the coating layer 1B is formed by coating, if the amount of the coating solution applied is increased, the surface roughness (SRz) of the coating layer 1B tends to become smaller. This will also be shown in the examples given later.

[0021] In short, it is presumed that by making the coating layer 1B appropriately thin, appropriate irregularities are formed on the surface of the coating layer 1B, thereby further improving the blocking resistance.

[0022] In the packaging film of this embodiment, the base material layer 1A may play an important role in bag formation by heat sealing. In other words, the base material layer 1A can be both a "base material layer" and a "heat seal layer" (the base material layer can also function as a heat seal layer). Specifically, the packaging film of this embodiment can be made into a bag and sealed by heat sealing without providing a separate heat seal layer (polyethylene usually has a low melting point). Not having to provide a separate heat seal layer is preferable in terms of simplifying the layer structure and reducing the number of materials used. However, this does not necessarily prevent the base layer 1A from having a multi-layer structure in this embodiment.

[0023] As described above, the packaging film of this embodiment has good blocking resistance despite its relatively simple structure. Moreover, the packaging film of this embodiment does not require a separate heat seal layer.

[0024] For reference, in the packaging film of this embodiment, by setting the thickness of the coating layer 1B to 0.3 to 4.5 μm, selecting a specific material as the material of the coating layer 1B, or designing the glass transition temperature and / or melting point of the coating layer 1B to be within a specific range, it is possible to obtain additional effects other than the improvement of blocking resistance. Specifically, the packaging film of this embodiment makes it easier to prepare a two-sided bag or a pouch package, and can improve the oxygen barrier property of the film. These will be described later.

[0025] The packaging film of this embodiment will now be described.

[0026] (Base material layer 1A) ·Materials for base layer 1A, etc. The base layer 1A contains one or more types of polyethylene. The polyethylene may be any of high density polyethylene, medium density polyethylene, linear low density polyethylene (L-LDPE), low density polyethylene, etc. Among these, linear low density polyethylene (L-LDPE) is preferred from the viewpoints of applicability to packaging applications and heat sealability.

[0027] Linear low density polyethylene (L-LDPE) is usually a copolymer of ethylene and a small amount of α-olefin. The type of α-olefin is not particularly limited. Typical α-olefins include 1-butene, 1-hexene, 4-methylpentene-1, and 1-octene.

[0028] In order to achieve a better balance of various properties such as heat resistance, transparency, mechanical properties, and rigidity, the density of the polyethylene is set to 900 to 965 kg / m 3 is preferable, and 900 to 940 kg / m 3 The density of the polyethylene can be measured in accordance with JIS K 7112 (1999).

[0029] From the viewpoint of flowability and moldability, the melt flow rate (MFR) of the polyethylene is preferably 0.5 g / 10 min or more, more preferably 1 g / 10 min or more, and even more preferably 2 g / 10 min or more. From the viewpoint of further stabilizing moldability, the MFR is preferably 30 g / 10 min or less, more preferably 20 g / 10 min or less, and even more preferably 10 g / 10 min or less. The MFR is measured in accordance with ASTM D1238 under conditions of 190°C and a load of 2.16 kg.

[0030] The substrate layer 1A may contain various additives, such as a heat stabilizer, a weather stabilizer, an antioxidant, an ultraviolet absorber, a lubricant, a slip agent, a nucleating agent, an antiblocking agent, an antistatic agent, an antifogging agent, a pigment, a dye, an inorganic or organic filler, and the like.

[0031] The substrate layer 1A may be made of a stretched film, a non-stretched film, or both a stretched film and a non-stretched film. In terms of increasing the mechanical strength of the film, the substrate layer 1A is preferably made of a stretched film, and more preferably made of a biaxially stretched film. On the other hand, in terms of increasing the heat seal strength, the surface of the substrate layer 1A opposite to the coating layer is preferably made of a non-stretched film.

[0032] In one embodiment, the base layer 1A may be a laminate in which two or more layers are laminated. When the base layer 1A is a laminate, the base layer 1A may contain two or more different polyethylene resins, and each layer may have a polyethylene resin composition different from each other. The substrate layer 1A, which is a laminate, may be produced by any method, such as a dry lamination method in which the layers are bonded together using an adhesive, a method in which the layers are bonded together during film formation, such as extrusion processing, without using an adhesive, or a combination of these methods.

[0033] The polyethylene-containing film constituting the base layer 1A can be obtained from, for example, Mitsui Chemicals Tocello Inc.

[0034] ·Thickness of base layer 1A The thickness of the base layer 1A is preferably 10 to 150 μm, more preferably 15 to 80 μm, and further preferably 30 to 60 μm. By making the thickness of the base layer 1A 10 μm or more, it is possible to increase the mechanical strength of the packaging film. By making the thickness of the base layer 1A 150 μm or less, it is possible to increase the handling property, bag-making suitability, light weight, etc. of the packaging film.

[0035] ·Physical properties and characteristics of base layer 1A The static friction coefficient μ of the surface of the base layer 1A is preferably 0.08 to 2.50, more preferably 0.09 to 2.00, even more preferably 0.10 to 1.50, particularly preferably 0.10 to 1.30, particularly preferably 0.10 to 0.60, and most preferably 0.10 to 0.35. For example, when a coating layer 1B is provided on one side of the base layer 1A by coating, the static friction coefficient having an appropriate value is expected to have the advantage of easily forming a thin and uniform coating layer 1B. In addition, the static friction coefficient having an appropriate value is expected to have the advantage of improving the handleability of the film.

[0036] When one side of the base layer 1A has been surface-treated (for example, corona treatment as described below), the static friction coefficient may be measured between untreated surfaces, between treated surfaces, or between an untreated surface and a treated surface. In particular, in terms of the advantage of "facilitating the formation of a thin and uniform coating layer 1B," the static friction coefficient μ 1 is preferably in the numerical range described above for μ. 1 is more preferably 0.10 to 0.80, further preferably 0.12 to 0.75, and particularly preferably 0.14 to 0.68.

[0037] The static friction coefficient of the base layer 1A can be adjusted, for example, by (i) subjecting the base layer 1A (polyethylene-containing film) to a surface treatment before the coating layer 1B or anchor coat layer is provided, or by (ii) adjusting the types and amounts of various additives in the base layer 1A (polyethylene-containing film). A specific example of (i) is surface modification by exposure to corona discharge (corona treatment). A specific example of (ii) is adjusting the amount or type of slip agent contained in the base layer 1A.

[0038] The static friction coefficient can be measured, for example, as described in the Examples below.

[0039] The ten-point average roughness SRz of the surface of the base layer 1A facing the coating layer 1B, as determined by three-dimensional surface measurement, is preferably 1.8 μm or more, more preferably 1.8 to 3.5 μm, and even more preferably 1.9 to 3.2 μm. The kurtosis SRku of the same surface obtained by three-dimensional surface measurement is preferably 120-300. The method for measuring SRz and SRku will be described in detail in the section explaining the coating layer 1B.

[0040] Although details will be described later, blocking resistance can be further improved by appropriately adjusting the surface roughness, etc., of the coating layer 1B. By adjusting the surface roughness of the base material layer 1A, it is easy to appropriately adjust the surface properties of the coating layer 1B. When coating layer 1B is thin, the surface roughness of base material layer 1A is likely to be reflected in the surface roughness of coating layer 1B. Therefore, for example, by adjusting the surface roughness of base material layer 1A to about the above-mentioned numerical values, the surface roughness of coating layer 1B can be easily adjusted to an appropriate value. The surface roughness of the base material layer 1A can be adjusted by the manufacturing method (method of forming a polyethylene-containing film), the use of appropriate additives, and appropriate surface treatment (corona treatment, etc.). Alternatively, a commercially available polyethylene-containing film having an appropriate surface roughness may be selected to form the base material layer 1A.

[0041] (Coating layer 1B) Coating layer 1B material As described above, the coating layer 1B contains a resin other than polyethylene. The coating layer 1B preferably contains one or more resins selected from the group consisting of polyurethane, polyvinyl alcohol, and polyvinylidene chloride. These resins are preferred in terms of improving oxygen barrier properties and further improving blocking resistance. Packaging films are often required to have oxygen barrier properties, and in this respect, it is preferable that the coating layer 1B contains a resin with high oxygen barrier properties, such as polyurethane, polyvinyl alcohol, or polyvinylidene chloride.

[0042] Furthermore, since the coating layer 1B contains a resin that is relatively more heat resistant than polyethylene, such as polyurethane, polyvinyl alcohol, or polyvinylidene chloride, the base layer 1A is easily melted by heat, while the coating layer 1B is not easily melted by heat. This is preferable in terms of suitability for manufacturing, for example, a two-pronged bag, which will be described later.

[0043] The ratio of the resin in the coating layer 1B is preferably 80% by mass or more, and more preferably 90% by mass or more.

[0044] When the coating layer 1B contains polyurethane, the type of polyurethane is not particularly limited as long as it contains a structural unit derived from a polyol and a structural unit derived from a polyisocyanate. The polyurethane may be any known or commercially available thermoplastic polyurethane, such as adipate ester-based thermoplastic polyurethane, polyether-based thermoplastic polyurethane, polycarbonate-based thermoplastic polyurethane, polycaprolactone-based thermoplastic polyurethane, etc.

[0045] When the coating layer 1B contains polyvinyl alcohol, the type of the polyvinyl alcohol is not particularly limited. Polyvinyl alcohol is usually obtained by saponifying polyvinyl acetate. Usable polyvinyl alcohols include so-called partially saponified polyvinyl alcohols in which several tens of percent of acetate groups remain, and fully saponified polyvinyl alcohols in which only a few percent of acetate groups remain. Of course, the method for producing polyvinyl alcohol is not particularly limited.

[0046] Polyvinyl alcohol may be a homopolymer polymerized using only vinyl acetate as a monomer, or a copolymer containing structural units derived from monomers other than vinyl acetate. When polyvinyl alcohol is a copolymer, the copolymerization components include (1) olefins such as ethylene, propylene, and 1-butene, (2) unsaturated carboxylic acids such as (meth)acrylic acid, crotonic acid, maleic acid, and fumaric acid, and their esters, salts, anhydrides, and amides, (3) unsaturated nitriles such as (meth)acrylonitrile, and (4) vinyl ethers such as methyl vinyl ether and ethyl vinyl ether.

[0047] Polyvinyl alcohol is available from, for example, Kuraray Co., Ltd.

[0048] When the coating layer 1B contains polyvinylidene chloride, the polyvinylidene chloride is not particularly limited as long as it contains a structural unit corresponding to vinylidene chloride monomer. The polyvinylidene chloride may be (i) only a structural unit derived from vinylidene chloride monomer, or (ii) a copolymer of vinylidene chloride monomer and another monomer copolymerizable with vinylidene chloride. The copolymer (ii) may be a copolymer having a ratio of structural units derived from vinylidene chloride monomer of 60 to 99% by mass and a ratio of structural units derived from monomers copolymerizable with vinylidene chloride of 1 to 40% by mass. Examples of monomers copolymerizable with vinylidene chloride include vinyl chloride, (meth)acrylonitrile, (meth)acrylic acid, (meth)acrylic acid alkyl esters (alkyl groups having 1 to 18 carbon atoms), maleic anhydride, itaconic acid, itaconic acid alkyl esters, vinyl acetate, ethylene, propylene, isobutylene, butadiene, etc.

[0049] Polyvinylidene chloride is available from, for example, Asahi Kasei Corporation.

[0050] Coating layer 1B thickness As described above, the thickness of the coating layer 1B is 0.3 to 4.5 μm. This thickness is preferably 0.3 to 2.5 μm, more preferably 0.3 to 2.0 μm, further preferably 0.4 to 1.8 μm, and particularly preferably 0.5 to 1.7 μm. When this thickness is appropriate, for example, blocking resistance can be further improved. The thickness of the coating layer 1B is preferably smaller than the thickness of the substrate layer 1A.

[0051] Roughness of coating layer 1B, etc. As described above, the coating layer 1B is present on the outermost surface of the packaging film. In other words, one side of the coating layer 1B is partially or entirely "exposed."

[0052] The ten-point average roughness SRz of the exposed surface of the coating layer 1B obtained by three-dimensional surface measurement is 0.50 μm or more, preferably 0.80 μm or more, more preferably 1.20 μm or more, and even more preferably 1.40 μm or more. There is no particular upper limit to SRz, but in reality, SRz is, for example, 3.2 μm or less, preferably 2.7 μm or less.

[0053] Furthermore, the kurtosis SRku of the exposed surface of the coating layer 1B obtained by three-dimensional surface measurement is preferably 25 or more, more preferably 50 or more, even more preferably 100 or more, particularly preferably 200 or more, particularly preferably 220 or more, and most preferably 240 or more. There is no particular upper limit to SRku, but in reality, SRku is, for example, 400 or less, preferably 300 or less, more preferably 250 or less.

[0054] To the best of the inventors' knowledge, among the surface roughness parameters, SRz and SRku in particular are correlated with blocking resistance. In this embodiment, the blocking resistance is further improved by both SRz and SRku being within their respective preferred ranges. In other words, the blocking resistance can be further improved by designing the packaging film with SRz and SRku considered as an integrated index.

[0055] SRz and SRku can be obtained by measuring the surface (exposed surface) of the coating layer 1B using a commercially available measuring device capable of measuring three-dimensional surface properties (surface roughness). For example, the measuring device may be a three-dimensional surface roughness measuring device SE-3500 manufactured by Kosaka Laboratory Co., Ltd., or a measuring device based on a similar measurement principle.

[0056] Additionally, SRz and SRku are parameters related to three-dimensional surface properties (area roughness), not two-dimensional surface properties (line roughness). Since it is considered important to consider "contact between film surfaces" in the occurrence and reduction of blocking, it makes sense to design and optimize the surface properties of the coating layer 1B based on three-dimensional surface properties, not two-dimensional surface properties.

[0057] Uniformity of coating layer 1B / oxygen permeability of the entire packaging film In the packaging film of this embodiment, the oxygen permeability of the film may be used as an index of whether the coating layer 1B is uniformly provided. In particular, when the coating layer 1B contains a resin material such as polyurethane, polyvinyl alcohol, or polyvinylidene chloride, the oxygen permeability of the film may be used as an index of the uniformity of the coating layer 1B. This is because the oxygen permeability of these resins is usually smaller than that of polyethylene. When the coating layer 1B is not uniform and has coating unevenness, pinholes, or the like, the oxygen permeability is considered to show a larger value.

[0058] Specifically, the oxygen permeability of the packaging film of this embodiment measured under conditions of a temperature of 23±2° C. and a humidity of 90±1.0% RH is 1.0×10 5 mL / (m 2 ·day·MPa) and / or the oxygen permeability measured under the conditions of temperature 23±2°C and humidity 50±1.0% RH is less than 1.0×10 5 mL / (m 2 ·day·MPa). Due to its low oxygen permeability, the packaging film of this embodiment can be preferably used, for example, as a packaging bag for food. Of course, the packaging film of this embodiment can be used for various purposes other than food.

[0059] The upper limit of the oxygen permeability (under conditions of temperature 23±2°C and humidity 90±1.0% RH, or under conditions of temperature 23±2°C and humidity 50±1.0% RH) is more preferably 5.0×10 4 mL / (m 2 ·day·MPa) or less, more preferably 1.0×10 4 mL / (m 2 ·day·MPa). In terms of oxygen barrier properties, the smaller the oxygen permeability, the better (ideally 0). However, from the perspective of practical design of packaging films, the oxygen permeability (under conditions of temperature 23±2°C and humidity 90±1.0% RH, or temperature 23±2°C and humidity 50±1.0% RH) should be, for example, 0.1 mL / (m 2 ·day·MPa) or more.

[0060] The oxygen permeability can be measured based on JIS K 7126.

[0061] Identification of coating layer 1B (material, thickness, etc.) The resin contained in the coating layer 1B can be determined, for example, by analyzing the infrared absorption spectrum of the coating layer 1B. In particular, in order to obtain the infrared absorption spectrum of a thin film such as the coating layer 1B, it is preferable to apply the attenuated total reflection method (ATR method).

[0062] For example, polyurethane, polyvinyl alcohol, and polyvinylidene chloride usually have absorption peaks in the following wave number regions, respectively. The resins contained in the coating layer 1B can be identified by these absorption peaks. Polyurethane: 3300±50cm -1 , 1700±50cm -1 , and 1500±50cm -1 Polyvinyl alcohol: 1450±50cm -1 , 1350±50cm -1 , 1110±50cm -1 , and 900±50cm -1 Polyvinylidene chloride: 1500±50cm -1 , and 650-800cm -1

[0063] Of course, the material constituting the coating layer 1B may be identified by a method other than the analysis of the infrared absorption spectrum.

[0064] The thickness of the coating layer 1B can be determined, for example, by using a known thickness gauge, such as the F20 series manufactured by Filmmetrics.

[0065] (Anchor coat layer) The packaging film of this embodiment may have an anchor coat layer between the coating layer 1B and the base layer 1A. In other words, in this embodiment, when forming the coating layer 1B on one side of the base layer 1A, an anchor coat layer may be provided in advance on one side of the base layer 1A. The presence of the anchor coat layer is expected to strengthen the adhesive strength between the coating layer 1B and the base layer 1A and to make the adhesive strength less likely to decrease over time (stabilize the adhesive strength). Of course, if the adhesive strength and its stability are sufficient for practical use, the anchor coat layer may not be necessary.

[0066] Materials for forming the anchor coat layer include anchor coat agents containing urethane resins, (meth)acrylic resins, etc. Commercially available anchor coat agents can be used as appropriate. When an anchor coat layer is provided, its thickness is usually 0.01 to 3 g / m2 in terms of non-volatile content. 2 , preferably 0.05 to 1 g / m 2 , preferably 0.05 to 0.5 g / m 2It is.

[0067] (Glass transition temperature and melting point of each layer, etc.) In the packaging film of this embodiment, by appropriately designing the glass transition temperature and melting point of each layer, an additional effect can be obtained, for example, of providing a packaging bag with excellent openability. In other words, the packaging film of this embodiment, in which the glass transition temperature and melting point of each layer are appropriately designed, is preferable as a film to be used for two-sided bags or pouch packaging (hereinafter sometimes referred to as "two-sided bags, etc.").

[0068] The "openability" will be explained below using the production of a two-sided pouch as an example.

[0069] A gassho bag is a bag made by gluing a single sheet of film together at the back and bottom, and is often used to package foods such as confectionery. The manufacturing process for gassho bags is usually as shown in Figure 2. I. First, fold the horizontally long film 1 into a cylindrical shape. II. Next, the back surface is heat-sealed to form a back heat-sealed portion 10. III. Then, the bottom surface is heat-sealed to provide a bottom heat-sealed portion 15. It is manufactured in the following procedure.

[0070] When a two-piece bag is manufactured using the above procedure, heat is applied twice by heat sealing to the area α enclosed by the dashed line in Fig. 2. Therefore, if the film 1 is a single-layer film consisting only of a base layer 1A containing polyethylene, part of the outer surface of the back heat-sealed portion 10 in the area α will be heat-sealed to the base layer 1A containing polyethylene at the location shown by the dashed line in the figure, as shown in Fig. 3. The presence or absence of such heat fusion of the back heat-sealed portion 10 is also referred to in this specification as the "heat-sealability of the back heat-sealed portion." (FIG. 3 is a schematic diagram showing the state of the portion α in FIG. 2 as viewed from the direction of the arrow in the case where the film 1 is a single-layer film consisting only of a base layer 1A containing polyethylene.) Such heat sealing is undesirable from the viewpoint of ease of opening the two-sided bag when a consumer opens it, and from the viewpoint of the aesthetic appearance of the two-sided bag, etc.

[0071] However, if coating layer 1B is present on one side of base layer 1A as in the packaging film of this embodiment, and coating layer 1B has a higher glass transition temperature than base layer 1A, the above problem can be alleviated. Specifically, a two-sided bag is manufactured using the packaging film of this embodiment in the above steps I to III so that the coating layer 1B, which has a higher glass transition temperature than the base layer 1A, is on the outer surface side. In this way, as shown in Fig. 4, the outer surface of the back heat seal portion 10 is prevented from melting or being thermally fused to other parts in the portion α. (FIG. 4 is a schematic diagram showing the state of the portion α in FIG. 2 when the film 1 includes a base layer 1A and a coating layer 1B, as viewed from the direction of the arrow shown in the figure.)

[0072] As a specific design, in the packaging film of this embodiment, when the glass transition temperature of coating layer 1B is Tgc and the glass transition temperature of base layer 1A is Tgs, the value of Tgc is preferably -25 to 120°C. The Tgc is more preferably from -25 to 120°C, further preferably from -22 to 115°C, and particularly preferably from -20 to 110°C. The Tgc-Tgs value (the difference between Tgc and Tgs) is preferably 90 to 245°C, more preferably 100 to 240°C, and further preferably 107 to 235°C. Moreover, Tgs is usually -130 to -120°C.

[0073] A Tgc-Tgs of 90 to 245°C, that is, a sufficiently large "difference" in the glass transition temperatures of the coating layer 1B and the base layer 1A, makes it easy to improve the ease of opening the two-sided bag and the aesthetic appearance of the two-sided bag, as described above. In addition, a Tgc of -25 to 120°C makes it possible to more reliably obtain the effects under the heat sealing conditions (temperature, time, etc.) normally applied in mass production.

[0074] The glass transition temperature can be determined, for example, by differential scanning calorimetry (DSC) based on JIS K 7121. If two or more glass transition points are observed in a DSC chart, the lower value is adopted as the glass transition temperature.

[0075] Incidentally, when the coating layer 1B has a melting point, the value is preferably 120 to 245°C, more preferably 120 to 230°C, further preferably 130 to 230°C, and particularly preferably 135 to 230°C. The melting point of the base layer 1A is preferably 110 to 133°C, and more preferably 112 to 131°C. The melting point, like the glass transition temperature, can be measured by differential scanning calorimetry (DSC).

[0076] In this embodiment, the glass transition temperature Tgc of the coating layer 1B is preferably sufficiently higher than the glass transition temperature Tgs of the base layer 1A. In addition, it is also preferable that Tgc itself is sufficiently high. As a result, by performing the heat sealing at an appropriate temperature in the heat sealing of III. above, it is possible to melt only the base layer 1A and not the coating layer 1B. In summary, in the packaging film of this embodiment, by appropriately designing the glass transition temperature and melting point of each layer, the effect of "producing two-sided bags that are easy to open and have a beautiful appearance" can be obtained.

[0077] (Layer composition) The packaging film of this embodiment has, for example, a two-layer structure as shown in FIG. On the other hand, as another example, the packaging film of this embodiment comprises a base layer 1A and a coating layer 1B provided on one side of the base layer 1A directly or via an anchor coat layer, and may also comprise additional layers as long as the thickness of the coating layer 1B is smaller than the thickness of the base layer 1A.

[0078] As yet another example, the packaging film of this embodiment may have, for example, two or more base layers 1A and / or two or more coating layers 1B. Specifically, as shown in FIG. 5, it may have a four-layer structure of base layer 1A-coating layer 1B-base layer 1A-coating layer 1B. It is clear that such a four-layer film also has good blocking resistance, which is insufficient for a single-layer polyethylene film. In addition, although it has a four-layer structure, few materials are used, so it is also preferable in terms of ease of recycling, etc.

[0079] In the four-layer packaging film shown in Fig. 5, the two base layers 1A may contain different polyethylenes (e.g., polyethylenes with different molecular weights or physical properties). Of course, the two base layers 1A may contain the same polyethylene resin. In the four-layer packaging film shown in Fig. 5, the two coating layers 1B may be made of different materials. For example, one of the two coating layers 1B may contain polyurethane and the other may contain polyvinylidene chloride. Of course, the two coating layers 1B may contain the same resin.

[0080] <Manufacturing method of packaging film> The packaging film of the present embodiment is preferably produced by applying a coating liquid (a resin solution or a resin dispersion) to one surface of a polyethylene-containing film. When providing an anchor coat layer, first, an anchor coat agent is applied to one side of the polyethylene-containing film and cured to form an anchor coat layer, and then the above-mentioned coating liquid (resin solution or resin dispersion) is applied.

[0081] The coating liquid may be either water-based or organic solvent-based. The coating liquid contains, for example, one or more resins such as polyurethane, polyvinyl alcohol, and polyvinylidene chloride as non-volatile components, and contains water and / or an organic solvent as volatile components. When the coating liquid contains an organic solvent, the organic solvent may be appropriately selected depending on the type of resin, etc. Examples of the organic solvent include ketones such as acetone, methyl ethyl ketone, cyclohexanone, etc.; ethers such as dioxane, diethyl ether, tetrahydrofuran, etc.; aromatic hydrocarbons such as benzene, toluene, xylene, etc.; esters such as ethyl acetate, butyl acetate, etc.; alcohols such as methanol, ethanol, 2-propanol (isopropyl alcohol), etc.; amides such as dimethylformamide, etc.; mixed solvents thereof, etc.

[0082] Examples of coating solutions containing polyurethane include the lineup of "Takenate," "Takelac," and "MT-Olestar" (all of which are registered trademarks) from Mitsui Chemicals, Inc. Among these lineups, some are water-based (water-dispersed type) and some are organic solvent-based. Of course, instead of using a commercially available coating solution, a suitable polyurethane may be dissolved / dispersed in water / organic solvent to prepare a coating solution.

[0083] The coating solution containing polyvinyl alcohol may be one in which polyvinyl alcohol is dissolved / dispersed in water / organic solvent. Since polyvinyl alcohol is usually hydrophilic, it is preferable to use water. However, in order to provide a uniform coating layer 1B on the polyethylene-containing film, it may be better to use water and an organic solvent in combination.

[0084] An example of an aqueous coating solution containing polyvinylidene chloride is a latex (emulsion) containing fine particles of polyvinylidene chloride. Commercially available products of this latex include the Saran Latex series manufactured by Asahi Kasei Corporation. The organic solvent-based coating liquid containing polyvinylidene chloride may be prepared by dissolving or dispersing polyvinylidene chloride in an organic solvent. Examples of the organic solvent that can be used are as described above.

[0085] The coating liquid is preferably water-based from the viewpoint of environmental load. However, when the coating liquid contains only water as a volatile solvent, it may be difficult to form a uniform coating layer 1B. In such a case, an organic solvent may be added to the water-based coating liquid. The organic solvent that can be used in this case is not particularly limited, but in terms of compatibility with water, alcohol-based solvents, specifically monohydric alcohols such as methanol, ethanol, and 2-propanol (isopropyl alcohol), and polyhydric alcohols such as ethylene glycol and glycerin, are preferable. When an organic solvent is added to a water-based coating liquid, the amount of the organic solvent is preferably 10 to 50 mass % of the total volatile components (total of water and organic solvent).

[0086] For various purposes, the coating liquid may contain various additive components, such as adhesive resins, silane coupling agents, and surfactants. In particular, it is preferable to appropriately adjust the amount of the surfactant in order to form a uniform coating layer 1B in which coating unevenness, pinholes, etc. are suppressed. The amount of the surfactant is preferably 0.8 to 7.5 mass %, more preferably 1.25 to 7.0 mass %, still more preferably 1.30 to 6.8 mass %, particularly preferably 1.30 to 1.80 mass %, and most preferably 1.30 to 1.55 mass %, based on the total non-volatile components of the coating liquid. In other words, the surfactant is preferably present in the coating layer 1B after the volatile components have evaporated in an amount of 0.8 to 7.5% by mass.

[0087] Incidentally, when the coating liquid contains a surfactant, the surface resistivity of the coating layer 1B becomes smaller. This is because the surfactant present on the surface of the coating layer 1B adsorbs moisture in the air. Therefore, the surface resistivity of the coating layer 1B can be used as an index of the surfactant content in the layer. Specifically, the surface resistivity of the coating layer 1B is, for example, 1×10 12 ~1×10 15 Ω, preferably 1×10 12 ~1×10 14 It is Omega. The surface resistivity is measured, for example, in accordance with the JIS K 6911 standard.

[0088] The non-volatile component concentration of the coating liquid is preferably 2 to 15% by mass, more preferably 3 to 12% by mass. By appropriately adjusting the non-volatile component concentration, it is easy to form a coating layer 1B with an appropriate thickness.

[0089] The amount of coating is not particularly limited. It may be appropriately adjusted so as to obtain a coating layer 1B of a desired thickness. For example, in order to obtain a relatively thin coating layer 1B as described above, the amount of coating is preferably 0.3 to 4.0 g / m2 in terms of non-volatile components. 2 , preferably 0.3 to 3.0 g / m 2 , preferably 0.3 to 2.5 g / m 2 , preferably 0.3 to 2.0 g / m 2 , and most preferably 0.4 to 1.8 g / m 2 It is.

[0090] The packaging film of this embodiment may be produced by (1) first applying a coating liquid containing a monomer and / or a prepolymer to one side of a polyethylene-containing film, and then (2) reacting the monomer and / or prepolymer on the polyethylene-containing film.

[0091] The specific method of application is not particularly limited, and any known method can be applied, for example, a method using a known device such as an air knife coater, a kiss roll coater, a metalling bar coater, a gravure roll coater, a reverse roll coater, a dip coater, or a die coater.

[0092] The specific method for drying after coating is not particularly limited, and any known method can be used, such as a method of drying using a known device such as an arch dryer, a straight bath dryer, a tower dryer, a drum dryer, or a floating dryer. Considering the heat resistance of the base layer 1A, the drying temperature is 50 to 95° C., preferably 55 to 90° C., and more preferably 60 to 85° C. The drying time is usually 5 seconds to 10 minutes, preferably 5 seconds to 3 minutes, and more preferably 5 seconds to 1 minute.

[0093] After coating and drying, an aging treatment may be further carried out, which is believed to strengthen the adhesive strength between the base layer 1A and the coating layer 1B, for example. Although the dried film can be left to stand at room temperature for aging treatment, it is preferable to perform the aging treatment in an oven or the like. From the viewpoints of shortening the treatment time and preventing damage to the film due to heating, the temperature of the aging treatment may be set in consideration of the heat resistance and melting point of the film substrate, and is preferably 30 to 80°C, more preferably 30 to 60°C, and even more preferably 30 to 50°C. The time for the aging treatment varies depending on the temperature conditions, but is preferably 6 to 168 hours, more preferably 12 to 120 hours, further preferably 12 to 96 hours, and particularly preferably 12 to 72 hours.

[0094] <Applications of packaging film / packaging> Specifically, the packaging film of this embodiment can be suitably used as a packaging film for packaging food, medicines, daily necessities, etc.; a film for vacuum insulation panels; a sealing film for sealing electroluminescence elements, solar cells, etc.; and the like.

[0095] The packaging film of the present embodiment can also be suitably used as a film constituting a package. The package is, for example, a packaging bag made of the packaging film of the present embodiment used for packaging an article, or an article packaged in the packaging bag. Depending on the application, only a part of the package may be made of the packaging film of the present embodiment, or substantially the entire package may be made of the packaging film of the present embodiment. The form of the package can be, for example, the above-mentioned two-sided bag or standing pouch (pouch packaging). As mentioned above, the two-sided bag is preferable in terms of ease of opening and appearance. The pouch packaging is preferable in terms of ensuring a sufficient volume of the packaging bag.

[0096] The article to be packaged is not particularly limited, and examples of the article include food, medicine, and electronic parts such as semiconductor elements and organic electroluminescence (EL) devices.

[0097] Just to be clear, when a package (such as a packaging bag) is formed using the packaging film of this embodiment, it is preferable that the coating layer 1B is on the outer surface in terms of effects such as blocking resistance.

[0098] Foods to be packaged include, in particular, dry goods (goods for which moisture absorption can be a problem), such as baked goods (cookies, biscuits, etc.), rice crackers, okaki, arare, popcorn, and other rice snacks, vegetable chips, snacks, sprinkles, and grain powders (wheat flour, rice flour, etc.). It is preferable to package foods (especially the above-mentioned dry foods) using a packaging bag made of the packaging film of this embodiment.

[0099] The method for producing a package from the packaging film is not particularly limited, and any method known in the field of packaging films / packaging bags, such as heat sealing or melt cutting, can be used as appropriate.

[0100] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various configurations other than those described above can be adopted. Furthermore, the present invention is not limited to the above-described embodiments, and modifications and improvements within the scope of the present invention are included in the present invention. EXAMPLES

[0101] The embodiments of the present invention will be described in detail based on Examples and Comparative Examples. It should be noted that the present invention is not limited to the Examples. In the following, exponential notation may be indicated by the symbol "E." For example, 1.3E-06 is 1.3 x 10 -6 means.

[0102] <Material preparation> The following materials were prepared. In the following description, "L-Smart", "TUX" and "Takelac" are registered trademarks.

[0103] (Polyethylene-containing film for constituting the base layer) C-1 Mitsui Chemicals Tocello Co., Ltd., L-Smart C-1 (thickness: 40 μm) C-1a (thickness: 40μm) The slip agent used in C-1 above has been reduced in amount. ·FC-S Mitsui Chemicals Tocello Co., Ltd., TUXFC-S (thickness: 50 μm) ·HZ Mitsui Chemicals Tocello Co., Ltd., TUXHZ (thickness: 50 μm) HZR-2 Mitsui Chemicals Tocello Co., Ltd., TUXHZR-2 (thickness: 50 μm)

[0104] The thickness, melting point, SRz, SRku, surface resistivity and dynamic friction coefficient of each film are as shown in the table below. The values ​​of SRz and SRku are the values ​​of the corona-treated surface of each film.

[0105] (Coating solution for forming anchor coat layer) A coating solution prepared by mixing Takelac A-310 manufactured by Mitsui Chemicals, Takenate A-3 manufactured by Mitsui Chemicals, and ethyl acetate to concentrations of 5.3 mass%, 0.1 mass%, and 94.6 mass%, respectively.

[0106] (Coating solution for forming coating layer) ·PU Takelac WPB-341 (a water-based dispersion containing polyurethane resin) manufactured by Mitsui Chemicals, Inc., was mixed with 2-propanol to make the mass ratio of water to 2-propanol the same. PVA A coating solution made by mixing Kuraray's Poval 105MC and water in a mass ratio of 10:90. ·PVDC Organic solvent-based coating liquid containing polyvinylidene chloride manufactured by Mitsui Chemicals MC Co., Ltd. (Polyvinylidene chloride is Saran Resin F216 manufactured by Asahi Kasei Corporation)

[0107] The non-volatile component concentrations of each coating liquid were PU: 9 mass %, PVA: 10 mass %, and PVDC: 5 mass %.

[0108] <Manufacturing of packaging films (forming coating layer)> When an anchor coat layer is provided between the substrate layer and the coating layer, a coating solution for forming an anchor coat layer is applied at 0.2 g / m using a Mayer bar (number #3). 2 The amount of the coating solution (calculated as non-volatile matter) was applied to the surface (corona-treated surface) of the polyethylene-containing film. The coating solution was then left to dry at 100° C. for 15 seconds to form an anchor coat layer.

[0109] A coating solution for forming a coating layer was applied using a Mayer bar to the corona-treated surface of the prepared polyethylene-containing film, or to the surface of the anchor coat layer if an anchor coat layer was provided. A Mayer bar #9 was used when the coating solution was PU or PVA, and #18 was used when the coating solution was PVDC. The amount of coating was the amount (g / m2) shown in the table below. 2 ) was adjusted. The combinations of the polyethylene-containing film and the coating liquid are shown in the table below.

[0110] After coating, the coating was dried with hot air at 100°C for 15 seconds when the coating solution was PU or PVDC, and at 70°C for 15 seconds when the coating solution was PVA.

[0111] After the drying treatment, aging treatment was performed at 40° C. for 24 hours when the coating liquid was PU or PVA, and at 40° C. for 48 hours when the coating liquid was PVDC. In this manner, a packaging film was produced.

[0112] <Measurements of various values> (Glass transition temperature (Tgs, Tgc), melting point (Tm)) Approximately 3.0 mg of each of the coating layer and base layer was taken from the packaging film to prepare samples for measurement. Each sample was subjected to DSC measurement to determine the glass transition temperature and melting point. The details of the DSC measurement are as follows. Measurement temperature steps: (i) hold at -50°C for 10 minutes → (ii) heat up and hold at 250°C for 10 minutes → (iii) lower the temperature and hold at -50°C for 10 minutes → (iv) heat up to 250°C Heating rate and cooling rate between steps (i) to (iv): 5°C / min Measurement atmosphere: Nitrogen gas

[0113] The glass transition temperature and melting point were determined based on the DSC curve obtained during the temperature increase (second run) between (iii) and (iv) above. For the glass transition temperature, an extrapolated glass transition onset temperature was used. The melting point was determined by measuring the peak top temperature of the melting peak.

[0114] (SRz and SRku) The three-dimensional surface properties of the coating layer surface and the corona-treated surface of the polyethylene-containing film (before the coating layer was formed) were measured using a three-dimensional surface roughness measuring instrument SE-3500 manufactured by Kosaka Laboratory Co., Ltd. The specific measurement conditions (device settings, etc.) are as follows. The data obtained by the measurement were analyzed using software to determine SRz and SRku.

[0115] ·Measurement length: MD direction; 400μm, TD direction; 1000μm Number of lines measured: TD direction lines; 201 Measurement pitch: MD direction; 0.5μm, TD direction; 2μm ·Z measurement magnification: 5000 X-feed speed: 0.2mm / s Low-frequency cutoff: 0.25mm High-frequency cut: R+W Leveling: Least Squares ·Z origin: Zero point adjustment using least squares method ·Stylus tip curvature radius: 2.0μm / 60℃ Measurement direction: Stylus moves parallel to MD direction -Analysis software: Built-in "3D surface roughness analysis program"

[0116] (Static friction coefficient of base layer) The measurement was performed according to the following procedure. (1) Two pieces of each polyethylene-containing film (hereinafter referred to as films 1 and 2) cut to a size of 50 mm x 75 mm were prepared. (2) The film 1 was fixed to a plate (hereinafter referred to as the inclined plate) whose inclination angle could be freely adjusted. (3) A rectangular member (bottom dimensions: 41 mm x 26 mm) with a bottom surface made of brass was fixed to film 2. A weight was then attached on top of the member so that the mass on film 2 was 150 g. (4) Film 2 was layered on top of film 1. (5) The inclined plate was gradually tilted from 0° at a speed of 1° / sec. The static friction coefficient was calculated from the angle θ when the upper film 2 started to slide (static friction coefficient = tan θ).

[0117] One side of the polyethylene-containing film used in this study was corona-treated, so the static friction coefficient was measured in three ways: between non-corona-treated surfaces, between a non-corona-treated surface and a corona-treated surface, and between corona-treated surfaces (as mentioned above, the coating solution was applied to the corona-treated surface).

[0118] (Surface resistivity) The packaging film was stored for 24 hours in an environment with a temperature of 23°C and a humidity of 50% RH. After that, the surface resistivity was measured using an Advantest digital ultra-high resistance / microcurrent meter (R8340A) and a resistivity chamber (R12704). The measurement conditions were an applied voltage of 560 V, an application time of 30 seconds, a temperature of 23°C, and a humidity of 50% RH.

[0119] (Coating layer thickness) The thickness of the coating layer was measured using a film thickness measuring instrument F20-UV (light source: halogen, measuring spot diameter: 1.5 mm) manufactured by Filmmetrics. In this study, the thickness was measured at three random points on one sample, and the average value of the thicknesses at these three points was determined as the thickness of the coating layer.

[0120] (Amount applied (non-volatile content)) If the coating liquid is PU The coating layer on the packaging film was wiped off with DMF (dimethylformamide).The amount of coating (converted into non-volatile components) was calculated from the change in mass before and after wiping. If the coating liquid is PVA The packaging film was immersed in boiling water to dissolve the coating layer on the packaging film. The coating amount (converted to non-volatile components) was calculated from the change in mass before and after immersion. If the coating liquid is PVDC The amount of Cl was calculated based on the intensity of the Cl-derived peak obtained by X-ray fluorescence analysis, using a calibration curve obtained using materials with known amounts of Cl.

[0121] The above various information is summarized in Tables 1 and 2. Table 1 summarizes the information on the base layer. Table 2 summarizes the information on the coating layer and the entire film. Table 2 also lists whether or not an anchor coat layer is present. Since none of the comparative films had a coating layer, there are no entries in Table 2 for the comparative films. In Tables 1 and 2, "-" in the surface resistivity column indicates that the surface resistivity was not measured. In Table 2, "-" in the column for the surfactant ratio indicates that the coating solution did not contain a surfactant. In Table 2, "-" in the column for melting point Tm indicates that no peak corresponding to the melting point was observed in the DSC measurement.

[0122] [Table 1]

[0123] [Table 2]

[0124] <Performance evaluation> (Blocking resistance) The evaluation was carried out according to the following procedure. (1) Two films were prepared for each Example and Comparative Example. (2)(i) Two films of each Example were stacked so that the coating layer surfaces were in contact with each other, or (ii) two samples of each Comparative Example were stacked so that the corona-treated surfaces were in contact with each other, with the MD / TD directions of the two samples being aligned. (3) The two overlapping samples were heated with a sealing iron under the following conditions: temperature 70°C, pressure 2.0 kgf, sealing time 60 seconds, and seal width 10 mm. This resulted in a sample in which the two samples were intentionally blocked. (4) After heating, the sample was allowed to cool naturally at room temperature. (5) Both sides of the sample were reinforced with commercially available adhesive tape (this is because if the blocking strength is too strong, the measurement sample will stretch in the tensile test described below in (6), making it impossible to measure the blocking strength accurately). (6) The sample cooled to room temperature was set in a tensile tester and pulled in the MD direction of the substrate film at a pulling speed of 5 mm / min. The load until the sample separated into individual pieces was recorded.

[0125] The maximum load recorded is shown in the "BL resistance strength" column in the table below. The smaller this value, the better the blocking resistance.

[0126] (Production suitability for folded bags, etc.: Evaluation of heat fusion of back heat seal part) In the following, the difficulty of heat sealing between coating layers under normal heat sealing conditions was evaluated to evaluate the "heat sealability of the back heat seal part" when manufacturing two-sided bags, etc. The specific evaluation procedure is as follows.

[0127] (1) Two film samples were prepared for each Example and Comparative Example. (2)(i) Two samples of each Example were stacked so that the surfaces of the coating layers were in contact with each other. Or, (ii) Two samples of each Comparative Example were stacked so that the corona-treated surfaces of the films used for the substrate layers were in contact with each other. At this time, the MD / TD directions of the two samples were aligned. (3) The two overlapping samples were heated using a sealing iron under the following conditions: temperature 140°C, pressure 1.5 kgf, sealing time 1.0 second, and seal width 10 mm. (4) After heating, the sample was allowed to cool naturally at room temperature.

[0128] The condition of the samples cooled to room temperature and the ease of separation of the two samples were evaluated on a three-point scale. ⊚ (Very good): No heat fusion was observed between the two samples. ◯ (Good): Slight heat fusion was observed between the two samples, but they could be easily separated by hand. × (bad): The two samples are clearly heat-sealed. When trying to separate them, the base layer stretches.

[0129] Incidentally, in the above (2)(i), the same procedures as those in the above (1) to (4) were carried out except that two samples of each Example were stacked so that the surfaces (opposite the coating layer) of the polyethylene-containing film used as the base layer were in contact with each other. Then, in all Examples, the polyethylene was sufficiently melted to form a heat-sealed portion.

[0130] (Oxygen permeability) The oxygen permeability of the packaging film was measured using a Mocon OX-TRAN2 / 21 device in accordance with JIS K 7126 under the following conditions: (i) temperature of 23±2°C and humidity of 90±1.0% RH, or (ii) temperature of 23±2°C and humidity of 50±1.0% RH. In the measurement, when the coating layer contains polyurethane, an aluminum mask is used to measure the oxygen permeability by reducing the measurement area to 1 / 10 or 1 / 50, and the oxygen permeability value obtained (raw data) is then multiplied by 10 or 50 to obtain the oxygen permeability. This is because polyurethane allows oxygen to pass through more easily than polyvinyl alcohol or polyvinylidene chloride, and there is a risk that the measurement will not be performed properly if the oxygen permeability is measured without a mask.

[0131] The results of the performance evaluation are summarized in the table below. Regarding the performance evaluation, the oxygen permeability is shown only for either the value measured under the conditions of a temperature of 23±2°C and a humidity of 90±1.0% RH or the value measured under the conditions of a temperature of 23±2°C and a humidity of 50±1.0% RH.

[0132] [Table 3]

[0133] As shown in Table 3, by providing a coating layer having a thickness of 0.3 to 4.5 μm on one side of a polyethylene film directly or via an anchor coat layer, it was possible to improve the blocking resistance compared to a "single-layer" polyethylene film. For example, the blocking resistance of the films of Examples 3 to 8 in which a coating layer was provided on one side of the base film C-1a was smaller than that of Comparative Example 2 (base film C-1a only).

[0134] Furthermore, the packaging films of the Examples showed good suitability for manufacturing of piping bags, etc., and good oxygen barrier properties. These effects are believed to be due to the appropriate design of the glass transition temperatures and their difference between the base layer and coating layer, and the selection of an appropriate resin for the coating layer, etc.

[0135] When the examples are analyzed in more detail, the following can be read, for example: The substrate film and the coating liquid were the same, but the thickness of the coating layer was different in Examples 3 to 6. It can be seen that the thickness of the coating layer affects the blocking resistance. From Examples 3 to 6, the blocking resistance was better when the coating layer was "moderately thin." [Explanation of symbols]

[0136] 1. Film 1A Base material layer 1B Coating layer 10 Back heat seal part 15 Bottom heat seal part

Claims

1. A base layer containing polyethylene (excluding a polyethylene-based resin stretched film in which the degree of crosslinking decreases toward the inside in the thickness direction of the film), A coating layer containing a resin other than polyethylene and provided in contact with one side of the base layer or provided via an anchor coat layer (excluding an anchor layer prepared from an isocyanate compound and an active hydrogen compound); Equipped with A part or the whole of one side of the coating layer is an exposed surface, The coating layer has a thickness of 0.3 to 4.5 μm. The thickness of the base layer is 10 to 150 μm, The oxygen permeability measured under the conditions of a temperature of 23±2°C and a humidity of 90±1.0% RH is 1.0×10 ５ mL / (m ２ and / or the oxygen permeability measured under conditions of a temperature of 23±2° C. and a humidity of 50±1.0% RH is less than 1.0×10 ５ mL / (m ２ .day.MPa).

2. The packaging film according to claim 1, The ten-point average roughness SRz of the exposed surface, as determined by three-dimensional surface measurement, is 0.50 μm or more.

3. The packaging film according to claim 1 or 2, A packaging film, wherein the exposed surface has a Kurtosis (Sku) value of 25 or more as determined by three-dimensional surface measurement.

4. The packaging film according to any one of claims 1 to 3, The packaging film, wherein the resin other than polyethylene is at least one selected from the group consisting of polyurethane, polyvinyl alcohol and polyvinylidene chloride.

5. The packaging film according to any one of claims 1 to 4, The packaging film has a glass transition temperature Tgc of -25 to 120°C and a glass transition temperature Tgc-Tgs of 90 to 245°C, where Tgc is the glass transition temperature of the coating layer and Tgs is the glass transition temperature of the substrate layer.

6. The packaging film according to any one of claims 1 to 5, The coating layer is a packaging film having no melting point or a melting point of 120 to 245°C.

7. The packaging film according to any one of claims 1 to 6, A packaging film, wherein the coefficient of static friction between the surfaces of the base layer is 0.08 to 2.

50.

8. The packaging film according to any one of claims 1 to 7, The coating layer comprises a surfactant, The surface resistivity of the coating layer is 1×10 １２ ~1×10 １５ Packaging film that is Omega.

9. The packaging film according to any one of claims 1 to 8, The coating layer comprises a surfactant, A packaging film, wherein the ratio of the surfactant in the coating layer is 0.8 to 7.5% by mass.

10. A packaging body formed from the packaging film according to any one of claims 1 to 9.

11. 11. The package of claim 10, A package having the coating layer on its outer surface.

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