Packaging film and packaging body

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 and having excellent openability.SOLUTION: A packaging film has a base material layer including polyethylene and a coating layer including a resin, provided in contact with one side of the base material layer or provided via an anchor coating layer. Taking the glass transition temperature of the coating layer to be Tgc and the glass transition temperature of the base material layer to be Tgs, the value of Tgc is from -25 to 120°C and the value of Tgc-Tgs is from 90 to 245°C.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 from the packaging film. [Background technology]

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

[0003] As an example, Patent Document 1 describes a laminated film formed by overlapping two biaxially oriented plastic films, each having a vinylidene chloride copolymer layer on one side, with the vinylidene chloride copolymer layer surfaces facing each other and thermocompression bonding (the adhesive strength of the two films is 10 to 50 gf / 15 mm). Patent Document 1 also describes that this laminated film is resistant to abrasion and punctures (pinholes are less likely to occur) 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 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 another example, Patent Document 3 describes a barrier film having a substrate 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 absorption peak heights A(1046) at wave numbers in the vicinity of this value 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] Japanese Patent Application Laid-Open No. 2009-241359 [Patent Document 3] Japanese Patent Application Laid-Open No. 2017-114079 Summary of the Invention [Problem to be solved by the invention]

[0007] With the rise in environmental awareness in recent years, and the issue of marine plastic pollution in particular, society has been scrutinizing packaging films. This has led to a greater demand than ever before for the promotion of packaging film recycling. In other words, there is a growing demand for packaging films to be designed and manufactured with "ease of recycling" in mind.

[0008] Many conventional packaging films have achieved desired effects (strength, gas barrier properties, etc.) by laminating multiple 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 multiple materials makes recycling difficult. From the viewpoint of facilitating recycling of packaging films, it is conceivable, for example, to make the packaging film have as simple a layer structure as possible.

[0009] In terms of simplifying the layer structure, the packaging film could conceivably be made into a "single layer" film. The present inventors conducted a preliminary study on various properties that may be required for packaging films using polyethylene film, a relatively low-cost and general-purpose packaging material. As a result of the study, it was found that a "single-layer" polyethylene film had room for improvement, for example, in terms of blocking resistance. Furthermore, when a package was produced using such a packaging film, there was room for improvement in the openability (ease of opening) of the package.

[0010] The present invention aims 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 and having excellent openability. [Means for solving the problem]

[0011] The present invention is as follows.

[0012] 1. a base layer containing polyethylene; a coating layer containing a resin, which is provided in contact with one surface of the base layer or provided via an anchor coat layer; A packaging film, wherein 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. 2. 1. The packaging film according to claim 1, The coating layer has a thickness of 0.3 to 2.0 μm. 3. 1. The packaging film according to 1. or 2., The packaging film has a thickness of the base layer of 10 to 150 μm. 4. The packaging film according to any one of 1. to 3., The coating layer of the packaging film comprises one or more resins selected from the group consisting of polyurethane, polyvinyl alcohol, and polyvinylidene chloride. 5. The packaging film according to any one of 1. to 4., The oxygen permeability measured under the conditions of temperature 23±2°C and humidity 90±1.0%RH is 1.0×10 5 mL / (m 2 ·day·MPa) and / or the oxygen permeability measured under the 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 Packaging film with a resistance of less than 1000kJ / day. 6. The packaging film according to any one of 1. to 5., The packaging film has a glass transition temperature of the substrate layer of -130 to -120°C. 7. The packaging film according to any one of 1. to 6., The coating layer is a packaging film having no melting point or a melting point of 120 to 230°C. 8. The packaging film according to any one of 1. to 7., The coating layer is present on the outermost surface of the packaging film, The packaging film has a ten-point average roughness SRz of the coating layer surface obtained by three-dimensional measurement of 0.50 μm or more. 9. The packaging film according to any one of 1. to 8., The coating layer is present on the outermost surface of the packaging film, A packaging film in which the kurtosis SRku of the coating layer surface obtained by three-dimensional measurement is 25 or more. 10. The packaging film according to any one of 1. to 9., The packaging film has a coefficient of static friction between the two surfaces of the base material layer of 0.08 to 2.50. 11. The packaging film according to any one of 1. to 10., The surface resistivity of the coating layer is 1×10 12 ~1×10 15Packaging film that is Omega. 12. The packaging film according to any one of 1. to 11., the coating layer comprises a surfactant; A packaging film, wherein the coating layer contains the surfactant in an amount of 0.8 to 7.5% by mass. 13. A package made of the packaging film according to any one of 1. to 12. 14. 13. The package according to claim 12, The coating layer is on the outer surface of the package. [Effects of the Invention]

[0013] The present invention provides 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 and having excellent openability, etc. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 2 is a diagram showing a schematic layer structure of a packaging film. [Figure 2] 10A and 10B are diagrams for explaining a method for manufacturing a "folded bag." [Figure 3] FIG. 3 is a diagram showing a schematic view of part 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 diagram showing the state of the part α in Figure 2 when viewed from the direction of the arrow shown in the figure (when the two-layered bag is made of a film). [Figure 5] FIG. 2 is a diagram schematically illustrating a layer structure of a packaging film different from that of FIG. 1. DETAILED DESCRIPTION OF THE INVENTION

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

[0016] In this specification, unless otherwise specified, the expression "X to Y" in the description of a numerical range means at least X and at most Y. For example, "1 to 5% by mass" means "at least 1% by mass and at most 5% by mass." In the description of groups (atomic groups) in this specification, when a notation does not specify whether the group is substituted or unsubstituted, it encompasses both groups having no substituents and groups having a substituent. For example, the term "alkyl group" encompasses not only alkyl groups having no substituents (unsubstituted alkyl groups) but also alkyl groups having a substituent (substituted alkyl groups). In this specification, the term "(meth)acrylic" represents a concept that encompasses both acrylic and methacrylic. The same applies to similar terms such as "(meth)acrylate."

[0017] <Packaging film> FIG. 1 is a diagram showing a schematic layer structure of the packaging film of the present embodiment. A base layer 1A containing polyethylene (hereinafter also referred to as base layer 1A), A coating layer containing a resin is provided in contact with one side of the base layer 1A or provided via an anchor coat layer. (The anchor coat layer is not shown in FIG. 1). When the glass transition temperature of coating layer 1B is Tgc and the glass transition temperature of substrate layer 1A is Tgs, the value of Tgc is -25 to 120°C and the value of Tgc-Tgs is 90 to 245°C. The substrate layer 1A may be a single layer or a laminate of two or more layers.

[0018] The packaging film of this embodiment has a specific coating layer (coating layer 1B) provided on one side of a polyethylene film (base layer 1A) to improve blocking resistance, which is insufficient with a single-layer polyethylene film, and to improve the ease of opening the packaging bag. The presence of coating layer 1B suppresses contact between substrate layers 1A, thereby improving blocking resistance. In particular, blocking resistance is improved by (i) having a glass transition temperature Tgc of coating layer 1B of −25 to 120°C and (ii) having a difference between Tgc and Tgs (glass transition temperature of the substrate layer) of 90 to 245°C. ((ii) indicates that the resin in coating layer 1B is less susceptible to molecular motion (thermal motion) than the resin in base layer 1A. It is believed that covering one side of a layer with easy molecular motion (base layer 1A) with a layer with difficult molecular motion (coating layer 1B) makes blocking less likely to occur. Furthermore, it is believed that when coating layer 1B satisfies condition (i), blocking between coating layers 1B is suppressed.)

[0019] In addition to improving blocking resistance, the packaging film of this embodiment can also provide packaging bags with excellent openability. In particular, the film is suitable as a film for pouch packaging such as a gusseted bag or a standing pouch (hereinafter sometimes referred to as "gusseted bag, etc.") in which heat sealing is performed in a state where the new bag overlaps an already heat-sealed portion during the heat-sealing process of bag production.

[0020] The "openability" will be explained below using the example of manufacturing a two-sided bag.

[0021] A gassho bag is a bag made by gluing together a single piece of film at the back and bottom, and is often used to package foods such as sweets. The manufacturing process for gassho bags (bag making) 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 form a bottom heat-sealed portion 15. It is manufactured in the following procedure.

[0022] When a two-sided bag is produced using the above procedure, heat is applied twice to the area α enclosed by the dashed line in Figure 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 area 10 in area α will be heat-sealed to the base layer 1A containing polyethylene at the location indicated by the dashed line in the figure, as shown in Figure 3. Whether or not the back heat-sealed area 10 is heat-sealed in this way is also referred to in this specification as the "heat-sealability of the back heat-sealed area." (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 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 when a consumer opens the two-sided bag and from the viewpoint of the aesthetic appearance of the two-sided bag.

[0023] However, by providing a coating layer 1B on one side of the base layer 1A, as in the packaging film of this embodiment, this problem can be alleviated. Specifically, using the packaging film of this embodiment, a two-sided bag is manufactured as described above in I to III, with the coating layer 1B facing the outer surface. This prevents the outer surface of the back heat-sealed portion 10 from melting or being thermally fused to other parts in the area α, as shown in Figure 4. (FIG. 4 is a schematic diagram illustrating 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.)

[0024] In this embodiment, the glass transition temperature Tgc of the coating layer 1B is sufficiently higher than the glass transition temperature Tgs of the base material layer 1A. Furthermore, Tgc itself is also sufficiently high. Therefore, by performing the heat-sealing at an appropriate temperature in the heat-sealing step III above, only the base material layer 1A melts, while the coating layer 1B does not melt. In summary, the packaging film of this embodiment has the effect of "making it possible to obtain a two-sided bag or the like that is easy to open and has an excellent appearance."

[0025] Since the base layer 1A also plays an important role in bag formation by heat sealing, it can be said that the base layer 1A can be both a "base layer" and a "heat seal layer" (the base layer can also serve as a heat seal layer). Furthermore, the packaging film of this embodiment can be used to form and seal bags by heat sealing without the need for a separate heat seal layer (polyethylene usually has a low melting point). Not needing 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.

[0026] As described above, the packaging film of this embodiment has good blocking resistance despite its relatively simple structure. Furthermore, the packaging film of this embodiment has the advantage that it can be used to produce, for example, a two-sided bag that is easy to open. Furthermore, the packaging film of this embodiment does not require a separate heat seal layer.

[0027] The packaging film of this embodiment will be described further.

[0028] (Base material layer 1A) -Materials of base layer 1A 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.

[0029] Linear low-density polyethylene (L-LDPE) is typically 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.

[0030] To achieve a better balance of various properties such as heat resistance, transparency, mechanical properties, and rigidity, the density of polyethylene is set to 900 to 965 kg / m 3 is preferable, and 900 to 940 kg / m 3 The density of polyethylene can be measured in accordance with JIS K 7112 (1999).

[0031] From the viewpoint of fluidity 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. Furthermore, 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 at 190°C under a load of 2.16 kg.

[0032] The substrate layer 1A may contain various additives, such as heat stabilizers, weather stabilizers, antioxidants, ultraviolet absorbers, lubricants, slip agents, nucleating agents, antiblocking agents, antistatic agents, antifogging agents, pigments, dyes, and inorganic or organic fillers.

[0033] The substrate layer 1A may be composed of a stretched film, a non-stretched film, or both a stretched film and a non-stretched film. From the viewpoint of increasing the mechanical strength of the film, the substrate layer 1A is preferably composed of a stretched film, and more preferably of a biaxially stretched film. On the other hand, from the viewpoint of increasing the heat seal strength, the surface of the substrate layer 1A opposite to the coating layer is preferably composed of a non-stretched film.

[0034] In one embodiment, the base layer 1A may be a laminate in which two or more layers are stacked. 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 base layer 1A, which is a laminate, may be produced by any method, such as a dry lamination method in which layers are bonded together using an adhesive, a method in which layers are bonded together during film formation such as extrusion processing without using an adhesive, or a combination of these methods.

[0035] The polyethylene-containing film that constitutes the base layer 1A can be obtained from, for example, Mitsui Chemicals Tocello Inc.

[0036] ·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 even more 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 improve the handling properties, bag-making suitability, lightweight properties, etc. of the packaging film.

[0037] ·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. Having an appropriate static friction coefficient is expected to have the advantage of facilitating the formation of a thin and uniform coating layer 1B, for example, when forming a coating layer 1B on one side of the base layer 1A by coating. Having an appropriate static friction coefficient is also expected to have the advantage of improving the handleability of the film.

[0038] When one side of the substrate 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, from the viewpoint of the advantage of "facilitating the formation of a thin and uniform coating layer 1B," it is preferable that the static friction coefficient μ1 between the surfaces of the substrate layer 1A facing the coating layer 1B be within the numerical range described above for μ. μ1 is more preferably 0.10 to 0.80, even more preferably 0.12 to 0.75, and particularly preferably 0.14 to 0.68.

[0039] 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 (ii) adjusting the type and amount of various additives in the base layer 1A (polyethylene-containing film). A specific example of (i) is surface modification by corona discharge irradiation (corona treatment). A specific example of (ii) is adjusting the amount or type of slip agent contained in the base material layer 1A.

[0040] The static friction coefficient can be measured, for example, as described in the Examples below.

[0041] The ten-point average roughness SRz of the surface of the base layer 1A on the side of the coating layer 1B, obtained by three-dimensional 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. Furthermore, the kurtosis SRku of the same surface obtained by three-dimensional measurement is preferably 120-300. The method for measuring SRz and SRku will be described in detail in the section describing the coating layer 1B.

[0042] As will be described in detail later, blocking resistance can be further improved by appropriately adjusting the surface roughness of coating layer 1B. Adjusting the surface roughness of base layer 1A makes it easier to appropriately adjust the surface properties of coating layer 1B formed thereon by coating. When coating layer 1B is thin, the surface roughness of base 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 layer 1A to about the above-mentioned numerical values, it is easy to set the surface roughness of coating layer 1B to an appropriate value. The surface roughness of the base material layer 1A can be adjusted by the manufacturing method (method for producing a polyethylene-containing film), the use of appropriate additives, or 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.

[0043] (Coating layer 1B) Coating layer 1B material 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 further improving oxygen barrier properties and blocking resistance. Packaging films are often required to have oxygen barrier properties, and therefore, the coating layer 1B preferably contains a resin with high oxygen barrier properties, such as polyurethane, polyvinyl alcohol, or polyvinylidene chloride.

[0044] The thickness of the coating layer 1B is preferably smaller than the thickness of the substrate layer 1A. The proportion of the resin in the coating layer 1B is preferably 80% by mass or more, and more preferably 90% by mass or more.

[0045] 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.

[0046] When the coating layer 1B contains polyvinyl alcohol, the type of 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.

[0047] 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, as well as 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.

[0048] Polyvinyl alcohol is available from, for example, Kuraray Co., Ltd.

[0049] When coating layer 1B contains polyvinylidene chloride, the polyvinylidene chloride is not particularly limited as long as it contains structural units corresponding to vinylidene chloride monomers. The polyvinylidene chloride may be (i) a copolymer containing only structural units derived from vinylidene chloride monomers, or (ii) a copolymer of vinylidene chloride monomers and other monomers copolymerizable with vinylidene chloride. Examples of copolymers (ii) include copolymers having a ratio of structural units derived from vinylidene chloride monomers 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, and butadiene.

[0050] Polyvinylidene chloride is available from, for example, Asahi Kasei Corporation.

[0051] Coating layer 1B thickness The thickness of the coating layer 1B is preferably 0.3 to 2.0 μm, more preferably 0.4 to 1.8 μm, and even more preferably 0.5 to 1.7 μm. By setting this thickness appropriately, (i) blocking resistance can be sufficiently improved, and (ii) it is possible to obtain a two-sided bag or the like in which fusion of the heat-sealed portions is sufficiently suppressed. More specifically, regarding (ii), it is possible to improve the ease of opening a two-sided bag, and in pouch packaging, it is possible to increase the volume of the packaging bag by fusion of the overlapping portions of the heat-sealed portions.

[0052] Surprisingly, the blocking resistance is not improved simply by increasing the thickness of coating layer 1B. However, by ensuring that coating layer 1B is neither too thin nor too thick, the blocking resistance can be further improved. This is presumably due to, for example, an excellent balance between the thickness of coating layer 1B and the unevenness of substrate layer 1A. More specifically, this is as follows.

[0053] When coating layer 1B is thin, it does not "completely fill" the irregularities on the surface of base layer 1A, and therefore the surface roughness of coating layer 1B (the surface opposite base layer 1A) is thought to reflect to some extent the properties of the surface of base layer 1A. In other words, when coating layer 1B is appropriately thin, it can be said that coating layer 1B "remains an appropriate amount of" the irregularities and roughness on the surface of base layer 1A. And / or, when forming the coating layer 1B by coating, if the amount of coating liquid applied is small, the volatile components will evaporate before the applied coating liquid is sufficiently leveled, i.e., flattened, and therefore the surface of the formed coating layer 1B is likely to be relatively rough. Incidentally, as an experimental fact, when the coating layer 1B is formed by coating, the surface roughness of the coating layer 1B tends to decrease as the amount of coating solution applied increases. This will also be shown in the examples below.

[0054] In short, it is believed that the surface of the coating layer 1B becomes appropriately rough when the coating layer 1B is appropriately thin. This "roughness" prevents the films from coming into close contact with each other (reducing the contact area between the films), which is thought to further improve blocking resistance.

[0055] Roughness of coating layer 1B, etc. Coating layer 1B is usually present on the outermost surface of the packaging film. In other words, one side of coating layer 1B is usually "exposed." The ten-point average roughness SRz of the coating layer 1B present on the outermost surface of the packaging film, obtained by three-dimensional measurement, is preferably 0.50 μm or more, more preferably 0.80 μm or more, even more preferably 1.20 μm or more, and particularly 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. Furthermore, the kurtosis SRku of the coating layer 1B present on the outermost surface of the packaging film, as determined by three-dimensional 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.

[0056] As described in the explanation of the "thickness" of the coating layer 1B, it is believed that the rough surface of the coating layer 1B further enhances the blocking resistance. Furthermore, it is estimated that, among the surface roughness parameters, SRz and SRku in particular are correlated with blocking resistance. In this embodiment, particularly, when both SRz and SRku are within their respective preferred ranges, the blocking resistance is further improved. In other words, by considering SRz and SRku as an integrated index when designing a packaging film, the blocking resistance can be further improved.

[0057] SRz and SRku can be determined by measuring the 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 the SE-3500 three-dimensional surface roughness measuring device manufactured by Kosaka Laboratory Co., Ltd., or a measuring device based on a similar measurement principle.

[0058] Additionally, SRz and SRku are parameters related to three-dimensional surface texture (area roughness), not two-dimensional surface texture (line roughness). Since it is considered important to consider "contact between film surfaces" in order to prevent or reduce blocking, it makes sense to design and optimize the surface texture of the coating layer 1B based on three-dimensional surface texture rather than two-dimensional surface texture.

[0059] Coating layer 1B uniformity / oxygen permeability In the packaging film of this embodiment, the oxygen permeability of the film can be used as an indicator of whether the coating layer 1B is uniformly provided, because the oxygen permeability of resin materials such as polyurethane, polyvinyl alcohol, and polyvinylidene chloride is usually lower than that of polyethylene.

[0060] 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 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). Due to its low oxygen permeability, the packaging film of this embodiment can be suitably used, for example, as a packaging bag for food. Of course, the packaging film of this embodiment can also be used for various purposes other than food.

[0061] The upper limit of the oxygen permeability (under conditions of a temperature of 23±2°C and a humidity of 90±1.0% RH, or under conditions of a temperature of 23±2°C and a humidity of 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 barrier properties, the smaller the oxygen permeability, the better (ideally 0). However, from the perspective of practical film design, 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.

[0062] Incidentally, the oxygen permeability can also be used as an index of whether the coating layer 1B is uniformly formed. In other words, if the coating layer 1B is not uniformly formed and there are coating irregularities or pinholes in the coating layer 1B, the oxygen permeability tends to show a larger value. Therefore, if the oxygen permeability measured under the above conditions is 1.0 × 10 5 mL / (m 2 When the compressive strength is less than 1 / 2·day·MPa, the coating layer 1B is properly formed, and an appropriate oxygen barrier property for a packaging film can be obtained.

[0063] The oxygen permeability can be measured in accordance with JIS K 7126.

[0064] 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, 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).

[0065] For example, polyurethane, polyvinyl alcohol, and polyvinylidene chloride typically exhibit absorption peaks in the following wavenumber regions: These absorption peaks can be used to identify the resin contained in coating layer 1B. 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

[0066] Naturally, the material constituting the coating layer 1B may be identified by a method other than the analysis of the infrared absorption spectrum.

[0067] The thickness of the coating layer 1B can be determined using, for example, a known film thickness measuring instrument, such as the F20 series manufactured by Filmmetrics.

[0068] (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 substrate layer 1A and to make the adhesive strength less likely to decrease over time (to stabilize the adhesive strength). Of course, if the adhesive strength and its stability are sufficient for practical use, the anchor coat layer may be omitted. 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 2 is.

[0069] (Glass transition temperature, melting point, size relationship of each layer, etc.) As described above, in the packaging film of this embodiment, when the glass transition temperature of the coating layer 1B is Tgc and the glass transition temperature of the base material layer 1A is Tgs, the value of Tgc is preferably -25 to 120°C. The Tgs 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 even more preferably 107 to 235°C. The Tgs is usually -130 to -120°C.

[0070] A Tgc-Tgs ratio of 90 to 245°C, i.e., a sufficiently large difference in the glass transition temperatures of coating layer 1B and base layer 1A, can more reliably achieve the aforementioned effect of "making it possible to obtain easily openable two-sided bags, etc." Furthermore, a Tgc of -25 to 90°C can more reliably achieve this effect under the heat sealing conditions (temperature, time, etc.) typically applied in mass production.

[0071] 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 on a DSC chart, the lower value is used as the glass transition temperature.

[0072] Incidentally, when the coating layer 1B has a melting point, the value is preferably 120 to 230°C, more preferably 130 to 230°C, and even more 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).

[0073] (Additional information about layer structure) 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 may have additional layers as long as it has 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.

[0074] 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. Furthermore, although it has a four-layer structure, few materials are used, making it preferable in terms of ease of recycling, etc.

[0075] In the four-layer packaging film shown in Fig. 5, the two base layers 1A may contain different polyethylenes (for example, polyethylenes with different molecular weights or physical properties), or, 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 from 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.

[0076] <Method of manufacturing packaging film> The packaging film of this 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 coating liquid (resin solution or resin dispersion) is applied.

[0077] The coating liquid may be 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, and cyclohexanone; ethers such as dioxane, diethyl ether, and tetrahydrofuran; aromatic hydrocarbons such as benzene, toluene, and xylene; esters such as ethyl acetate and butyl acetate; alcohols such as methanol, ethanol, and 2-propanol (isopropyl alcohol); amides such as dimethylformamide; and mixed solvents thereof.

[0078] 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-dispersible) and others 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.

[0079] Examples of coating solutions containing polyvinyl alcohol include those in which polyvinyl alcohol is dissolved or dispersed in water or an organic solvent. Since polyvinyl alcohol is usually hydrophilic, it is preferable to use water. However, in order to form a uniform coating layer 1B on the polyethylene-containing film, it may be better to use water and an organic solvent in combination.

[0080] 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 usable organic solvents are as described above.

[0081] From the viewpoint of environmental impact, the coating liquid is preferably water-based. However, if the coating liquid contains only water as a volatile solvent, it may be difficult to form a uniform coating layer 1B. In such cases, 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 are preferred, specifically, monohydric alcohols such as methanol, ethanol, and 2-propanol (isopropyl alcohol), and polyhydric alcohols such as ethylene glycol and glycerin. 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).

[0082] 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 surfactant in order to form a uniform coating layer 1B in which coating unevenness, pinholes, etc. are suppressed. The amount of surfactant is preferably 0.8 to 7.5 mass %, more preferably 1.25 to 7.0 mass %, even 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 %, of the total non-volatile components of the coating liquid. In other words, the surfactant preferably exists in an amount of 0.8 to 7.5% by mass in the coating layer 1B after the volatile components have evaporated.

[0083] Incidentally, the surface resistivity of the coating layer 1B decreases when the coating liquid contains a surfactant. This is because the surfactant present on the surface of the coating layer 1B adsorbs moisture from the air. Therefore, the surface resistivity of the coating layer 1B can be used as an indicator 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, according to the standard of JIS K 6911.

[0084] The concentration of nonvolatile components in the coating solution is preferably 2 to 15% by mass, more preferably 3 to 12% by mass. By appropriately adjusting the concentration of nonvolatile components, it is easy to form a coating layer 1B with an appropriate thickness.

[0085] The amount of coating is not particularly limited, but it is preferable to adjust it appropriately so that the coating layer 1B has a desired thickness. For example, to obtain a relatively thin coating layer 1B (about 0.3 to 2.0 μm) as described above, the amount of coating is preferably 0.3 to 4.0 g / m2 in terms of nonvolatile 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 is.

[0086] 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 (2) then reacting the monomer and / or prepolymer on the polyethylene-containing film.

[0087] The specific coating method is not particularly limited, and any known method can be used, such as 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.

[0088] The specific method for drying after application is not particularly limited, and any known method can be applied, 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.

[0089] After application and drying, an aging treatment may be further carried out, which is thought to strengthen the adhesive strength between the substrate layer 1A and the coating layer 1B, for example. The dried film can be left standing at room temperature for aging treatment, but is preferably aged 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, still more preferably 12 to 96 hours, and particularly preferably 12 to 72 hours.

[0090] <Packaging film applications / packaging materials> Specifically, the packaging film of this embodiment can be suitably used as a packaging film for packaging food, medicines, everyday items, etc.; a film for vacuum insulation panels; a sealing film for sealing electroluminescence elements, solar cells, etc.; and the like.

[0091] The packaging film of this 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 this embodiment and used for packaging an article, or an article packaged in such a packaging bag. Depending on the application, only a portion of the package may be made of the packaging film of this embodiment, or substantially the entire package may be made of the packaging film of this embodiment. The form of the package can be, for example, the aforementioned two-sided bag or standing pouch (pouch packaging). As mentioned above, two-sided bags are preferable in terms of ease of opening and appearance. Pouch packaging is preferable because it can ensure sufficient volume for the packaging bag.

[0092] There are no particular limitations on the type of product to be packaged, and examples of the product include food, medicine, and electronic components such as semiconductor elements and organic electroluminescence devices.

[0093] Just to be clear, when constructing a package (such as a packaging bag) using the packaging film of this embodiment, in order to reliably obtain the property that is "suitable for manufacturing two-sided bags," it is preferable that the base layer 1A be on the inner surface side and the coating layer 1B be on the outer surface side.

[0094] Foods to be packaged include, in particular, dry goods (items for which moisture absorption can be a problem), such as baked goods (cookies, biscuits, etc.), rice crackers such as rice crackers, okaki (rice crackers), arare (pickled rice crackers), popcorn, 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.

[0095] The method for producing a package from a packaging film is not particularly limited, and any method known in the field of packaging films / packaging bags, such as heat sealing or fusion cutting, can be used as appropriate.

[0096] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various other configurations may be adopted. Furthermore, the present invention is not limited to the above-described embodiments, and modifications and improvements within the scope of achieving the object of the present invention are included in the present invention. [Example]

[0097] The embodiments of the present invention will be described in detail based on Examples and Comparative Examples. However, 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, 1.1E-06 is 1.1 x 10 -6 means.

[0098] <Material preparation> The following materials were prepared. In the following description, "L'Smart", "TUX" and "Takelac" are registered trademarks.

[0099] (Polyethylene-containing film for forming the base layer) C-1 Mitsui Chemicals Tocello Co., Ltd., L-Smart C-1 (thickness: 40 μm) C-1a (thickness: 40 μm) The same as C-1 above, but with a reduced amount of slip agent. ·FC-S Mitsui Chemicals Tohcello Co., Ltd., TUXFC-S (thickness: 50 μm) HZ Mitsui Chemicals Tohcello Co., Ltd., TUXHZ (thickness: 50 μm) HZR-2 Mitsui Chemicals Tohcello Co., Ltd., TUXHZR-2 (thickness: 50 μm)

[0100] The thickness, melting point, SRz, SRku, surface resistivity, and dynamic friction coefficient of each film are as shown in the table below. The SRz and SRku values ​​are those of the corona-treated surface of each film.

[0101] (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 in amounts of 5.3 mass%, 0.1 mass%, and 94.6 mass%, respectively.

[0102] (Coating liquid for forming coating layer) ·PU 2-propanol was added to Takelac WPB-341 (a water-based dispersion containing polyurethane resin) manufactured by Mitsui Chemicals, Inc., to make the mass ratio of water to 2-propanol the same. PVA A coating solution prepared 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)

[0103] The concentrations of nonvolatile components in each coating liquid were PU: 9 mass %, PVA: 10 mass %, and PVDC: 5 mass %.

[0104] <Manufacturing packaging film (forming coating layer)> When an anchor coat layer is provided between the substrate layer and the coating layer, a coating solution for forming the anchor coat layer is applied in a thickness of 0.2 g / m using a Mayer bar (number #3). 2 The coating was applied to the surface (corresponding to the corona treatment side) of the polyethylene-containing film in an amount of 100°C (based on non-volatile content), and then allowed to stand for 15 seconds to dry, forming an anchor coat layer.

[0105] The coating solution for forming the 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 #9 Mayer bar was used when the coating solution was PU or PVA, and a #18 Mayer bar was used when the coating solution was PVDC. The amount of coating was the amount (g / m) shown in the table below. 2 ) was adjusted to be The combinations of polyethylene-containing films and coating solutions are shown in the table below.

[0106] 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.

[0107] After the drying treatment, the coating was aged at 40°C for 24 hours when the coating liquid was PU or PVA, or at 40°C for 48 hours when the coating liquid was PVDC. In this way, a packaging film was produced.

[0108] <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 serve as measurement samples. 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) Cool down and hold at -50°C for 10 minutes → (iv) Heat up to 250°C Temperature increase and decrease rates between steps (i) to (iv): 5°C / min Measurement atmosphere: Nitrogen gas

[0109] The glass transition temperature and melting point were determined based on the DSC curve obtained during the temperature increase between (iii) and (iv) above (second run). For the glass transition temperature, the extrapolated glass transition onset temperature was used. The melting point was determined as the peak top temperature of the melting peak.

[0110] (SRz and SRku) The three-dimensional surface texture of the coating layer surface and the corona-treated surface of the polyethylene-containing film (before the coating layer was formed) was measured using a three-dimensional surface roughness measuring instrument, SE-3500, manufactured by Kosaka Laboratory Co., Ltd. The specific measurement conditions (instrument settings, etc.) were as follows. The data obtained from the measurements were then analyzed using software to determine SRz and SRku.

[0111] ·Measurement length: MD direction; 400μm, TD direction; 1000μm Number of lines measured: 201 lines in the TD direction Measurement pitch: MD direction: 0.5 μm, TD direction: 2 μm ·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 alignment using least squares method ·Stylus tip curvature radius: 2.0μm / 60℃ Measurement direction: Stylus moves parallel to the MD direction Analysis software: Built-in "3D surface roughness analysis program"

[0112] (Static friction coefficient of the base layer) Measurement was carried out according to the following procedure. (1) Two pieces of each polyethylene-containing film (hereinafter referred to as films 1 and 2) were prepared, each cut to a size of 50 mm x 75 mm. (2) The film 1 was fixed to a plate (hereinafter referred to as an inclined plate) whose inclination angle could be freely adjusted. (3) A rectangular member (41 mm x 26 mm) with a brass bottom was fixed to film 2. A weight was then attached to the member so that the mass of film 2 was 150 g. (4) Film 2 was placed on top of film 1. (5) The inclined plate was gradually tilted from 0° at a rate of 1° / sec. The static friction coefficient was calculated from the angle θ when the upper film 2 began to slide (static friction coefficient = tan θ).

[0113] 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).

[0114] (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.

[0115] (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 locations on one sample, and the average value of the thicknesses at these three locations was taken as the thickness of the coating layer.

[0116] (Amount applied (non-volatile component equivalent)) If the coating liquid is PU The coating layer on the packaging film was wiped off using DMF (dimethylformamide), and the amount of coating (converted to 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, and the coating amount (in terms of non-volatile components) was calculated from the change in mass before and after immersion. If the coating liquid is PVDC The calculation was based on the intensity of the Cl-derived peak obtained by X-ray fluorescence analysis, using a calibration curve obtained using materials with known Cl amounts.

[0117] The above information is summarized in Tables 1 and 2. Table 1 summarizes information about the substrate layer. Table 2 summarizes information about 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 column for surface resistivity indicates that the surface resistivity was not measured. In Table 2, "-" in the column for surfactant ratio indicates that the coating liquid 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.

[0118] [Table 1]

[0119] [Table 2]

[0120] <Performance evaluation> (blocking resistance) The evaluation was carried out according to the following procedure. (1) Two films were prepared for each example or comparative example. (2) (i) Two films from each Example were stacked together with their coating layers facing each other. Alternatively, (ii) two samples from each Comparative Example were stacked together with their corona-treated surfaces facing 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 at a temperature of 70°C, a pressure of 2.0 kgf, a sealing time of 60 seconds, and a sealing width of 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) The sample was reinforced with commercially available adhesive tape on both the front and back sides (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 rate of 5 mm / min. The load required for the sample to separate into individual pieces was recorded.

[0121] 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.

[0122] (Production suitability for folded bags, etc.: Evaluation of heat fusion properties of the back heat seal part) Below, we evaluated the "heat-sealing property of the back heat-sealed part" when manufacturing two-sided bags, etc., by evaluating the difficulty of heat-sealing between coating layers under normal heat-sealing conditions. The specific evaluation procedure is as follows.

[0123] (1) Two film samples were prepared for each example or 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. Alternatively, (ii) two samples of each Comparative Example were stacked so that the corona-treated surfaces of the films used as 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 conditions of a temperature of 140°C, a pressure of 1.5 kgf, a sealing time of 1.0 second, and a sealing width of 10 mm. (4) After heating, the sample was allowed to cool naturally at room temperature.

[0124] The state of the sample cooled to room temperature and the ease of separation of the two samples were evaluated using the following 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.

[0125] 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 of the films used as the base layers were in contact with each other. As a result, in all Examples, the polyethylene was sufficiently melted to form a heat-sealed portion.

[0126] (oxygen permeability) Using a Mocon OX-TRAN2 / 21 device, the oxygen permeability of packaging films was measured in accordance with JIS K 7126 under the following conditions: (i) a temperature of 23±2°C and a humidity of 90±1.0% RH, or (ii) a temperature of 23±2°C and a humidity of 50±1.0% RH. In measurements where the coating layer contains polyurethane, an aluminum mask is used to reduce the measurement area to 1 / 10 or 1 / 50, and the oxygen permeability is then measured, and the obtained oxygen permeability value (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 measuring oxygen permeability without a mask may result in inaccurate measurements.

[0127] The results of the performance evaluation are summarized in the table below. Regarding the oxygen permeability performance evaluation, only one of the values ​​measured under the conditions of a temperature of 23±2°C and a humidity of 90±1.0% RH and the other under the conditions of a temperature of 23±2°C and a humidity of 50±1.0% RH is shown.

[0128] [Table 3]

[0129] In each example, by providing a coating layer with an appropriate glass transition temperature Tgc (Tgc of -25 to 120°C, and Tgc-Tgs of 90 to 245°C) on one side of the base layer, it was possible to improve 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 lower than that of Comparative Example 2 (base film C-1a only).

[0130] In each example, by providing a coating layer with an appropriate glass transition temperature Tgc on one side of the base material layer, good suitability for manufacturing two-sided bags and the like could be obtained.

[0131] Furthermore, in each example, the oxygen permeability could be reduced by providing a coating layer with an appropriate glass transition temperature Tgc on one side of the substrate layer (see examples and comparative examples that share a common substrate layer).

[0132] When the examples are analyzed in more detail, the following can be read, for example: In Examples 3 to 6, the substrate film and coating solution were the same, but the thickness of the coating layer was different. In Examples 5 and 6, where the coating layer was relatively thick, the blocking resistance was relatively high. On the other hand, in Examples 3 and 4, where the coating layer was relatively thin, the blocking resistance was relatively low. Generally speaking, it would seem that the thicker the coating layer, the lower the blocking resistance. However, Examples 3 to 6 show that the blocking resistance was lower when the coating layer was "moderately thin" (i.e., the blocking resistance was better). [Explanation of symbols]

[0133] 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 (excluding a coating layer made of a PVA coating film containing an aqueous coating agent in which the ratio of polyvinyl alcohol (A) to an aqueous anchor agent (B) is 99 / 1 to 80 / 20, and a coating layer made of a gas barrier layer containing a gas barrier organic polymer and a large number of ultrafine powders made of at least one material selected from inorganic compounds and metals dispersed in the polymer) provided in contact with one side of the base layer or provided via an anchor coat layer, a packaging film in which, when the glass transition temperature of the coating layer is Tgc and the glass transition temperature of the base layer is Tgs, the value of Tgc is −25 to 120° C. and the value of Tgc−Tgs is 90 to 245° C., and the surface of the coating layer opposite to the base layer is an exposed surface; A packaging film, wherein the coating layer comprises polyvinyl alcohol.

2. The packaging film according to claim 1, The coating layer has a thickness of 0.3 to 2.0 μm.

3. The packaging film according to claim 1 or 2, The packaging film, wherein the thickness of the substrate layer is 10 to 150 μm.

4. The packaging film according to any one of claims 1 to 3, 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 A packaging film having a compressive strength of less than 1 / 2 day / MPa.

5. The packaging film according to any one of claims 1 to 4, The packaging film has a glass transition temperature of -130 to -120°C.

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 230°C.

7. The packaging film according to any one of claims 1 to 6, The coating layer surface has a ten-point average roughness SRz of 0.50 μm or more, as determined by three-dimensional measurement.

8. The packaging film according to any one of claims 1 to 7, A packaging film in which the kurtosis SRku of the coating layer surface obtained by three-dimensional measurement is 25 or more.

9. The packaging film according to any one of claims 1 to 8, A packaging film, wherein the coefficient of static friction between the two surfaces of the base layer is 0.08 to 2.

50.

10. The packaging film according to any one of claims 1 to 9, The surface resistivity of the coating layer is 1×10 １２ ~1 x 10 １５ Packaging film that is Ω.

11. The packaging film according to any one of claims 1 to 10, the coating layer comprises a surfactant; A packaging film, wherein the proportion of the surfactant in the coating layer is 0.8 to 7.5% by mass.

12. A package made of the packaging film according to any one of claims 1 to 11.

13. 13. The package of claim 12, The coating layer is on the outer surface of the package.

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