Packaging films and packaging materials

Abstract

To provide a packaging film having improved blocking resistance and oxygen barrier property, which have been defects 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 at least one resin selected from the group consisting of polyurethane, polyvinyl alcohol and polyvinylidene chloride, provided in contact with one side of the base material layer or provided via an anchor coating layer. The coating layer is thinner than the base material layer in thickness.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to packaging films and packaging bodies. More specifically, it relates to packaging films and packaging bodies constructed from such packaging films. [Background technology]

[0002] In the field of packaging films, attempts to improve various performance aspects by devising the materials used and layer configurations are well known.

[0003] As an example, Patent Document 1 describes a laminated film obtained by heat-pressing two biaxially oriented plastic films, each having a vinylidene chloride copolymer layer on one side, with the vinylidene chloride copolymer layers overlapping (the adhesive strength of the two films is 10-50 gf / 15 mm). Patent Document 1 states that this laminated film is resistant to abrasion and puncture (less prone to pinholes) and also has excellent gas barrier properties.

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

[0005] As yet another example, Patent Document 3 describes a barrier film comprising a base layer, an inorganic layer, and a polyvinylidene chloride resin layer in that order. When the infrared absorption spectrum of the polyvinylidene chloride resin layer of this barrier film was measured, it was 1070 cm⁻¹. -1 Absorption peak height A(1070) in the vicinity of wavenumber is 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 is excellent in blocking resistance.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] In recent years, due to the increasing environmental awareness, especially the spotlight on the problem of marine plastic pollution, packaging films have been under the strict scrutiny of society. And, more than ever, the promotion of recycling of packaging films is being demanded. In other words, there is a growing need to design and manufacture packaging films considering "ease of recycling".

[0008] Most of the conventional packaging films have obtained desired effects (such as strength and gas barrier properties) by laminating multiple types of materials. For example, the multilayer film described in Patent Document 2 includes at least four layers: a gas barrier layer, an overcoat layer, an adhesive layer, and a sealant layer. However, the lamination of multiple types of materials has led to difficulty in recycling. From the perspective of making the packaging film easy to recycle, 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, theoretically, it is conceivable to make the packaging film a "single layer". The inventors preliminarily studied various properties that may be required for a packaging film using a polyethylene film, which is a relatively low-cost and general-purpose packaging material. As a result, the "single-layer" polyethylene film did not show sufficient performance in terms of blocking resistance and oxygen barrier properties. In addition, when a package was manufactured using such a packaging film, there was room for improvement in the opening property (ease of opening) of the package.

[0010] An object of the present invention is to provide a packaging film with improved blocking resistance and oxygen barrier properties, which are insufficient in a single-layer polyethylene film, and a package excellent in opening property constituted by such a packaging film.

Means for Solving the Problems

[0011] The present invention is as follows.

[0012] 1. A base material layer containing polyethylene, A coating layer containing one or more resins selected from the group consisting of polyurethane, polyvinyl alcohol, and polyvinylidene chloride, and provided in contact with one side of the base material layer or provided via an anchor coat layer, A packaging film comprising the above, wherein the thickness of the coating layer is smaller than the thickness of the base material layer. 2. The packaging film according to 1., The packaging film wherein the thickness of the coating layer is 0.3 to 2.0 μm. 3. The packaging film according to 1. or 2., The packaging film wherein the thickness of the base material layer is 10 to 150 μm. 4. The packaging film according to any one of 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 2The oxygen permeability is less than 1.0 × 10⁻¹⁰ MPa (day·MPa) and / or measured under conditions of a temperature of 23 ± 2°C and a humidity of 50 ± 1.0% RH. 5 mL / (m 2 Packaging film with a pressure of less than MPa (·day·MPa). 5. A packaging film described in any one of 1. to 4., When the glass transition temperature of the coating layer is Tgc and the glass transition temperature of the substrate layer is Tgs, A packaging film with a Tgc value of -25 to 120°C and a Tgc-Tgs value of 90 to 245°C. 6. The packaging film described in 5. Tgs is a packaging film with a temperature range of -130 to -120°C. 7. A packaging film described in any one of items 1 to 6, The coating layer is a packaging film that has no melting point or has a melting point of 120 to 230°C. 8. A packaging film described in any one of items 1 to 7, The coating layer is present on the outermost surface of the packaging film. A packaging film having a ten-point average roughness SRz of the surface of the coating layer, obtained by three-dimensional measurement, of 0.50 μm or more. 10. A packaging film described in any one of items 1 to 9, The coating layer is present on the outermost surface of the packaging film. A packaging film in which the kurtosis SRku obtained by three-dimensional measurement of the surface of the coating layer is 25 or greater. 11. A packaging film described in any one of items 1 to 10, A packaging film wherein the static friction coefficient between the two sides of the base layer is 0.08 to 2.50. 12. A packaging film described in any one of items 1 to 11, The surface resistivity of the coating layer is 1 × 10⁻⁶ 12 ~1 × 10 15 A packaging film that is Ω in shape. 13. A packaging film described in any one of items 1 to 12, The aforementioned coating layer contains a surfactant, A packaging film in which the proportion of the surfactant in the coating layer is 0.8 to 7.5% by mass. 13. A package made of the packaging film described in any one of items 1 to 12. 14. The packaging described in 13. A packaging body having the aforementioned coating layer on its outer surface. [Effects of the Invention]

[0013] The present invention provides a packaging film with improved blocking resistance and oxygen barrier properties, which are insufficient with a single layer of polyethylene film, and a package made of such a packaging film that has excellent openability and other properties. [Brief explanation of the drawing]

[0014] [Figure 1] This diagram schematically shows the layer structure of a packaging film. [Figure 2] This is a diagram illustrating the manufacturing method of a "gusseted bag". [Figure 3] This diagram schematically represents the state of part α in Figure 2 when viewed from the direction of the arrow shown in the figure (when the gusseted bag is made of a single layer of film). [Figure 4] This diagram schematically represents the state of part α in Figure 2 when viewed from the direction of the arrow shown in the figure (when the gusseted bag is made of a two-layer film structure). [Figure 5] This figure schematically shows a different layer structure of packaging film than that shown in Figure 1. [Modes for carrying out the invention]

[0015] Embodiments of the present invention will be described in detail below with reference to the drawings. In all drawings, similar components are denoted by the same reference numerals, and explanations are omitted where appropriate. To avoid complexity, (i) if there are multiple identical components in the same drawing, only one will be assigned a reference numeral, and none of them will be assigned a reference numeral; and (ii) especially in Figure 2 and later, components similar to those in Figure 1 may not be assigned a reference numeral again. All drawings are for illustrative purposes only. The shapes and dimensional ratios of the components shown in the drawings do not necessarily correspond to actual items.

[0016] In this specification, the notation "X~Y" in descriptions of numerical ranges means "X or greater and Y or less" unless otherwise specified. For example, "1~5 mass%" means "1 mass% or greater and 5 mass% or less". In this specification, when a group (atomic group) is not specified as substituted or unsubstituted, it includes both unsubstituted and substituted groups. For example, "alkyl group" includes not only unsubstituted alkyl groups but also substituted alkyl groups. In this specification, the term "(meth)acrylic" refers to a concept that encompasses both acrylic and methacrylic. The same applies to similar terms such as "(meth)acrylate."

[0017] <Packaging film> Figure 1 is a schematic diagram showing the layer structure of the packaging film of this embodiment. The packaging film of this embodiment is • A polyethylene-containing base layer 1A (hereinafter also referred to as base layer 1A) A coating layer 1B (hereinafter also referred to as coating layer 1B) containing one or more resins selected from the group consisting of polyurethane, polyvinyl alcohol, and polyvinylidene chloride, It is equipped with. The thickness of the coating layer 1B is less than the thickness of the substrate layer 1A. The coating layer 1B is provided so as to be in contact with one side of the substrate layer 1A, or an anchor coat layer is provided between the coating layer 1B and the substrate layer 1A (the anchor coat layer is not shown in Figure 1). The polyethylene substrate layer 1A may be a single layer or a laminate consisting of two or more layers.

[0018] The packaging film of this embodiment is provided with a coating of an appropriate material on the polyethylene film in order to improve the blocking resistance and oxygen barrier properties that are insufficient in a single-layer polyethylene film. In particular, polyethylene film has low oxygen barrier properties (high oxygen permeability). Therefore, in this embodiment, in order to impart oxygen barrier properties, a coating layer 1B containing one or more resins selected from the group consisting of polyurethane, polyvinyl alcohol, and polyvinylidene chloride is provided in contact with one side of the substrate layer 1A, or via an anchor coat layer. The coating layer 1B enhances oxygen barrier properties. Furthermore, the coating layer 1B adjusts the surface condition, reducing contact between the substrate layers 1A and improving blocking resistance.

[0019] Furthermore, in this embodiment, the thickness of the coating layer 1B is smaller than the thickness of the base layer 1A. In other words, a relatively small amount of material is required to provide the coating layer 1B. Moreover, there are no other layers between the base layer 1A and the coating layer 1B. These features are advantageous in terms of environmental performance and recyclability. Incidentally, the blocking resistance can be further enhanced by appropriately adjusting the "thickness" of coating layer 1B. This will be explained in more detail later.

[0020] In addition to improving oxygen barrier properties and blocking resistance, the packaging film of this embodiment can also produce packaging bags with excellent openability. In particular, it is suitable as a film for pouch packaging such as gusseted bags and standing pouches (hereinafter sometimes referred to as "gusseted bags, etc.") in which the heat sealing process of the bag making is performed while overlapping with an already heat-sealed portion.

[0021] The following explanation of "openability" will be given using the manufacturing of gusseted bags as an example.

[0022] A gassho bag is a bag made by bonding a single film at the back and bottom, and is widely used for packaging food products such as confectionery. The manufacturing (bag making) of gassho bags is usually as shown in Figure 2. I. First, fold the horizontally oriented film 1 into a cylindrical shape. II. Next, the back surface is heat-sealed to create a back heat-sealed portion 10. III. Then, the bottom surface is heat-sealed to form the bottom heat-sealed portion 15. It is manufactured using the following procedure.

[0023] When manufacturing a gusseted bag using the procedure described above, the portion α enclosed by the dashed line in Figure 2 is subjected to heat twice by heat sealing. Therefore, if the film 1 is a single-layer film consisting only of a base layer 1A containing polyethylene, as shown in Figure 3, a portion of the outer surface of the back heat-seal portion 10 in α will be heat-fused to the base layer 1A containing polyethylene at the location indicated by the dashed line in the figure. In this specification, the presence or absence of such heat fusion of the back heat-seal portion 10 is also referred to as the "heat-fusibility of the back heat-seal portion." (Figure 3 schematically represents the state of portion α in Figure 2 when viewed from the direction of the arrow shown in the figure, assuming that film 1 is a single-layer film consisting only of a substrate layer 1A containing polyethylene.) Such heat sealing is undesirable from the standpoint of ease of opening for consumers and from the standpoint of aesthetics of the gusseted bag.

[0024] However, the above problem can be improved by having a coating layer 1B on one side of the base layer 1A, as in the packaging film of this embodiment. Specifically, the gusseted bag is manufactured as described in I. to III. above using the packaging film of this embodiment, so that the side with the coating layer 1B is the outer surface. In this way, as shown in Figure 4, melting of the outer surface of the back heat-seal portion 10 or heat fusion with other parts is suppressed in portion α. (Figure 4 schematically represents the state of portion α in Figure 2 when viewed from the direction of the arrow shown in the figure, in the case where film 1 comprises a base layer 1A and a coating layer 1B.)

[0025] The polyurethane, polyvinyl alcohol, and polyvinylidene chloride contained in coating layer 1B are generally less susceptible to melting by heat than the polyethylene contained in base layer 1A. Therefore, by performing heat sealing at an appropriate temperature during the heat sealing process described in III above, only the base layer 1A can be melted, while the coating layer 1B remains unmelted. In summary, the packaging film of this embodiment provides the effect of "making it possible to obtain gusseted bags and the like that are easy to open and have a superior appearance."

[0026] Since the base layer 1A also plays an important role in bag making by heat sealing, it can be said that the base layer 1A is 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 made and sealed by heat sealing without the need to provide a separate heat seal layer. Not needing to provide a separate heat seal layer is preferable in that it simplifies the layer structure and reduces the number of materials used. However, in this embodiment, it is not necessarily prohibited for the base layer 1A to have a multilayer structure.

[0027] As described above, despite having a relatively simple structure, the packaging film of this embodiment has good blocking resistance. In addition, the packaging film of this embodiment can have the merit of being able to manufacture, for example, a gusseted bag that is easy to open. Furthermore, it is not necessary to separately provide a heat-sealing layer for the packaging film of this embodiment.

[0028] Continue the description of the packaging film of this embodiment.

[0029] (Base material layer 1A) ·Regarding the material of the base material layer 1A The base material layer 1A contains one or more types of polyethylene. The polyethylene can be any of high-density polyethylene, medium-density polyethylene, linear low-density polyethylene (L-LDPE), low-density polyethylene, etc. Among these, from the viewpoints of applicability to packaging uses and heat-sealing properties, linear low-density polyethylene (L-LDPE) is preferred.

[0030] 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, 1-octene, etc.

[0031] From the viewpoint of further improving the balance of various properties such as heat resistance, transparency, mechanical properties, and rigidity, the density of the polyethylene is preferably 900 - 965 kg / m 3 and more preferably 900 - 940 kg / m 3 The density of the polyethylene can be measured according to JIS K 7112 (1999).

[0032] From the viewpoint of fluidity and moldability, the melt flow rate (MFR) of 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 under conditions of 190°C and a load of 2.16 kg.

[0033] The substrate layer 1A may contain various additives. Examples of additives include heat stabilizers, weather stabilizers, antioxidants, UV absorbers, lubricants, slip agents, nucleating agents, antiblocking agents, antistatic agents, antifogging agents, pigments, dyes, inorganic or organic fillers, and the like.

[0034] The base layer 1A may be composed of a stretched film, an unstretched film, or both a stretched film and an unstretched film. In terms of increasing the mechanical strength of the film, it is preferable that the base layer 1A is composed of a stretched film, and more preferably a biaxially oriented film. On the other hand, in terms of increasing the heat seal strength, it is preferable that the side of the base layer 1A opposite to the coating layer is composed of an unstretched film.

[0035] In one embodiment, the base material layer 1A may be a laminate in which two or more layers are stacked. If 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 different polyethylene resin composition from the others. The laminated base layer 1A may be manufactured by any method. For example, it may be manufactured by a dry lamination method using an adhesive, a method of bonding during film formation such as extrusion without using an adhesive, or a combination of these methods.

[0036] The polyethylene-containing film constituting the base layer 1A can be obtained, for example, from Mitsui Chemicals Tohcello Co., Ltd.

[0037] • 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, the mechanical strength of the packaging film can be increased. By making the thickness of the base layer 1A 150 μm or less, the handling properties, suitability for bag making, and lightness of the packaging film can be improved.

[0038] • 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, especially preferably 0.10 to 0.60, and most preferably 0.10 to 0.35. Having an appropriate static friction coefficient offers the advantage of easily forming a thin and uniform coating layer 1B when, for example, a coating layer 1B is applied to one side of the base layer 1A by coating. Furthermore, an appropriate static friction coefficient also offers the advantage of improving the handling of the film.

[0039] If one side of the substrate layer 1A is surface-treated (for example, corona treatment as described later), the static friction coefficient can be measured between untreated surfaces, between treated surfaces, or between an untreated surface and a treated surface. In particular, regarding the advantage of "ease of forming a thin and uniform coating layer 1B," it is preferable that the static friction coefficient μ1 between the surfaces of the substrate layer 1A and the coating layer 1B in contact is within the numerical range of μ described above. 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.

[0040] The static friction coefficient of the base layer 1A can be adjusted, for example, by (i) applying a surface treatment to the base layer 1A (polyethylene-containing film) before the coating layer 1B is applied, or by (ii) adjusting the types and amounts of various additives in the base layer 1A (polyethylene-containing film). Specific examples of (i) include surface modification by corona discharge irradiation (corona treatment). Specific examples of (ii) include adjusting the amount and type of slip agent contained in the base layer 1A.

[0041] The static friction coefficient can be measured, for example, as in the embodiment described later.

[0042] The ten-point average roughness SRz obtained by three-dimensional measurement of the surface of the substrate layer 1A in contact with the coating layer 1B 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 obtained by three-dimensional measurement of the same surface is preferably 120 to 300. The methods for measuring SRz and SRku will be described in detail in the section describing coating layer 1B.

[0043] As will be explained in more detail later, the blocking resistance can be further improved by appropriately adjusting the surface roughness of the coating layer 1B. By adjusting the surface roughness of the substrate layer 1A, it is easier to appropriately adjust the surface properties of the coating layer 1B that is formed on top of it by application. When the coating layer 1B is thin, the surface roughness of the substrate layer 1A is easily reflected in the surface roughness of the coating layer 1B. Therefore, by adjusting the surface roughness of the substrate layer 1A to approximately the above value, it is easier to set the surface roughness of the coating layer 1B to an appropriate value. The surface roughness of the base layer 1A can be adjusted by its manufacturing method (method for forming polyethylene-containing film), the use of appropriate additives, and appropriate surface treatment (corona treatment, etc.). Alternatively, a commercially available polyethylene-containing film with an appropriate surface roughness may be selected as the base layer 1A.

[0044] (Coating layer 1B) • Material of coating layer 1B The coating layer 1B contains one or more resins selected from the group consisting of polyurethane, polyvinyl alcohol, and polyvinylidene chloride. The proportion of resin in the coating layer 1B is preferably 80% by mass or more, and more preferably 90% by mass or more.

[0045] If coating layer 1B contains polyurethane, the type of polyurethane is not particularly limited. The polyurethane can be any type that contains structural units derived from polyols and structural units derived from polyisocyanates. The polyurethane may be a known or commercially available thermoplastic polyurethane. Examples of such polyurethanes include adipate-ester based thermoplastic polyurethanes, polyether-based thermoplastic polyurethanes, polycarbonate-based thermoplastic polyurethanes, and polycaprolactone-based thermoplastic polyurethanes.

[0046] If the coating layer 1B contains polyvinyl alcohol, the type of polyvinyl alcohol is not particularly limited. Polyvinyl alcohol is typically obtained by saponifying polyvinyl acetate. Usable polyvinyl alcohols include so-called partially saponified polyvinyl alcohol, in which several tens of percent of acetate groups remain, and fully saponified polyvinyl alcohol, in which only a few percent of acetate groups remain. Of course, the method of producing polyvinyl alcohol is not particularly limited.

[0047] Polyvinyl alcohol may be a homopolymer polymerized using only vinyl acetate as a monomer, or it may be a copolymer containing structural units derived from monomers other than vinyl acetate. When polyvinyl alcohol is a copolymer, the copolymer 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, 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 can be obtained from companies such as Kuraray Co., Ltd.

[0049] If the coating layer 1B contains polyvinylidene chloride, the polyvinylidene chloride is not particularly limited as long as it contains structural units corresponding to vinylidene chloride monomer. The polyvinylidene chloride may (i) contain only structural units derived from vinylidene chloride monomer, or (ii) may be a copolymer of vinylidene chloride monomer and other monomers copolymerizable with vinylidene chloride. Examples of copolymers of (ii) include copolymers in which the proportion of structural units derived from vinylidene chloride monomer is 60 to 99% by mass, and the proportion of structural units derived from monomers copolymerizable with vinylidene chloride is 1 to 40% by mass. Examples of monomers copolymerizable with vinylidene chloride include vinyl chloride, (meth)acrylonitrile, (meth)acrylic acid, alkyl (meth)acrylate (alkyl group with 1 to 18 carbon atoms), maleic anhydride, itaconic acid, alkyl itaconic acid, vinyl acetate, ethylene, propylene, isobutylene, butadiene, and the like.

[0050] Polyvinylidene chloride can be obtained from companies such as Asahi Kasei Corporation.

[0051] • Thickness of coating layer 1B 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 ensuring this thickness is appropriate, (i) blocking resistance can be greatly improved, and (ii) fusion of heat-sealed parts can be greatly suppressed, resulting in gusseted bags and the like. More specifically regarding (ii), in gusseted bags, ease of opening can be improved, and in pouch packaging, the volume of the packaging bag can be increased by preventing fusion of the overlapping heat-sealed parts.

[0052] Surprisingly, it's not simply a matter of coating layer 1B being thicker that improves blocking resistance; rather, the coating layer 1B being neither too thin nor too thick can further enhance blocking resistance. This is presumed to be due to, for example, a delicate balance between the thickness of coating layer 1B and the surface irregularities of the substrate layer 1A. More specifically, it is as follows:

[0053] If the coating layer 1B is thin, it will not completely fill in the irregularities on the surface of the substrate layer 1A. Therefore, the surface roughness of the surface of the coating layer 1B (the side opposite to the substrate layer 1A) will, to some extent, reflect the surface properties of the substrate layer 1A. In other words, if the coating layer 1B is moderately thin, it can be said that the coating layer 1B will leave a moderate amount of the irregularities and roughness on the surface of the substrate layer 1A. Furthermore, when a coating layer 1B is provided by application, if the amount of coating liquid applied is insufficient, the volatile components will evaporate before the applied coating liquid has sufficiently leveled, i.e., flattened, so the surface of the formed coating layer 1B is likely to be relatively rough. Incidentally, experimental results show that when coating layer 1B is applied by coating, increasing the amount of coating solution tends to reduce the surface roughness of coating layer 1B. This will also be shown in the examples described later.

[0054] In short, it is thought that the surface of coating layer 1B becomes moderately rough because the coating layer 1B is moderately thin. This "roughness" prevents the films from sticking together when they come into 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. The coating layer 1B is typically located on the outermost surface of the packaging film. In other words, one side of the coating layer 1B is usually "exposed". Furthermore, 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 obtained by three-dimensional measurement of the coating layer 1B present on the outermost surface of the packaging film is preferably 25 or higher, more preferably 50 or higher, even more preferably 100 or higher, particularly preferably 200 or higher, especially preferably 220 or higher, and most preferably 240 or higher. There is no particular upper limit to SRku, but in reality, SRku is, for example, 400 or less, preferably 300 or less, and more preferably 250 or less.

[0056] As explained in the section describing the "thickness" of coating layer 1B, the rough surface of coating layer 1B is thought to further enhance its blocking resistance. Furthermore, it is presumed that among the surface roughness parameters, SRz and SRku in particular are correlated with blocking resistance. In this embodiment, in particular, the blocking resistance is further improved when both SRz and SRku are within their respective preferred numerical ranges. In other words, by designing the packaging film considering SRz and SRku as an integrated indicator, the blocking resistance can be further improved.

[0057] SRz and SRku can be determined by measuring the surface of coating layer 1B using a commercially available measuring device capable of measuring three-dimensional surface properties (surface roughness). Examples of such measuring devices include the SE-3500 three-dimensional surface roughness measuring machine from Kosaka Laboratory Co., Ltd., or other measuring devices based on similar measurement principles.

[0058] It should be added that SRz and SRku are parameters related to three-dimensional surface properties (surface roughness), not two-dimensional surface properties (linear roughness). Since it is considered important to consider "contact between film surfaces" when it comes to blocking occurrence and reduction, it is reasonable to design and optimize the surface properties of coating layer 1B based on three-dimensional surface properties rather than two-dimensional surface properties.

[0059] • Uniformity / oxygen permeability of coating layer 1B 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. This is because polyurethane, polyvinyl alcohol, and polyvinylidene chloride are materials with lower oxygen permeability compared to polyethylene.

[0060] Specifically, the oxygen permeability of the packaging film of this embodiment, measured under conditions of a temperature of 23±2℃ and a humidity of 90±1.0%RH, is 1.0×10⁻⁶. 5 mL / (m 2 The oxygen permeability measured under conditions of less than 1.0 × 10⁻¹⁰ MPa (day·MPa) and / or 23±2°C and 50±1.0%RH is 1.0 × 10⁻¹⁰ MPa. 5 mL / (m 2 It is preferable that the pressure is less than (·day·MPa). Due to its low oxygen permeability, the packaging film of this embodiment can be preferably applied to food packaging bags, for example. Of course, the packaging film of this embodiment can be used for various applications other than food.

[0061] The upper limit of oxygen permeability (under conditions of temperature 23±2℃ and humidity 90±1.0%RH, or under conditions of temperature 23±2℃ 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 It is less than or equal to (·day·MPa). In terms of barrier properties, generally speaking, a lower oxygen permeability is preferable (ideally 0). However, from the standpoint of practical film design, an oxygen permeability (under conditions of 23±2°C and 90±1.0%RH humidity, or 23±2°C and 50±1.0%RH humidity) of, for example, 0.1 mL / (m²) is desirable. 2 It is above (·day·MPa).

[0062] Incidentally, oxygen permeability can also be used as an indicator of whether or not the coating layer 1B is uniformly applied. In other words, if the coating layer 1B is not uniformly applied and there are uneven coatings 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 × 10⁻⁶ 5 mL / (m 2 By having a pressure of less than MPa (day·MPa), the coating layer 1B is properly formed, and appropriate oxygen barrier properties can be obtained for use as a packaging film.

[0063] Oxygen permeability can be measured according to JIS K 7126.

[0064] Identification of coating layer 1B (material, thickness, etc.) Whether or not the coating layer 1B contains one or more resins selected from the group consisting of polyurethane, polyvinyl alcohol, and polyvinylidene chloride 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 total internal reflection (ATR) method.

[0065] In each resin, absorption peaks are typically observed in the following wavenumber regions, and these absorption peaks allow for the identification of the resin contained in coating layer 1B. • Polyurethane: 3300 ± 50 cm -1 , 1700±50cm -1 , and 1500±50cm -1 • Polyvinyl alcohol: 1450 ± 50 cm -1 , 1350±50cm -1 , 1110±50cm -1 , and 900±50cm -1 • Polyvinylidene chloride: 1500 ± 50 cm -1 , and 650~800cm -1

[0066] Naturally, the material constituting the coating layer 1B may be identified by methods other than infrared absorption spectroscopy.

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

[0068] (Glass transition temperature, melting point, relative sizes, etc. for each layer) 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 substrate layer 1A is Tgs, the value of Tgc is preferably -25 to 120°C, more preferably -22 to 115°C, and even more preferably -20 to 110°C. Furthermore, 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. Furthermore, Tgs is typically between -130 and -120°C.

[0069] The fact that the Tgc-Tgs range is 90-245°C, meaning that the "difference" in glass transition temperature between the coating layer 1B and the substrate layer 1A is sufficiently large, makes it possible to more reliably obtain the aforementioned effect of "being able to obtain easy-to-open gusseted bags, etc." Furthermore, the fact that the Tgc range is -25-120°C makes it possible to more reliably obtain this effect under the heat sealing conditions (temperature, time, etc.) that are normally applied during mass production.

[0070] 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 the DSC chart, the lower value should be adopted as the glass transition temperature.

[0071] Incidentally, if the coating layer 1B has a melting point, its value is preferably 120 to 230°C, more preferably 130 to 230°C, and even more preferably 135 to 230°C. Furthermore, 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).

[0072] (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 stabilizes the adhesion between the coating layer 1B and the substrate layer 1A, and also improves the oxygen barrier properties. Materials for forming the anchor coat layer include anchor coat agents containing urethane resin or (meth)acrylic resin. Commercially available anchor coat agents can be used as appropriate. When an anchor coat layer is provided, its thickness is typically 0.01 to 3 g / m² in terms of non-volatile content.2 Preferably 0.05 to 1 g / m 2 , more preferably 0.05~0.5 g / m 2 That is the case.

[0073] (Supplementary information on layer structure) The packaging film of this embodiment has a two-layer structure, for example, as shown in Figure 1 above. On the other hand, as another example, the packaging film of this embodiment comprises a base layer 1A and a coating layer 1B in contact with one side of the base layer 1A, and may also include an additional layer as long as the thickness of the coating layer 1B is less than the thickness of the base layer 1A.

[0074] As yet another example, the packaging film of this embodiment may, for example, comprise two or more base layer 1A and / or two or more coating layer 1B. Specifically, as shown in Figure 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 with a single-layer polyethylene film. Furthermore, although it has a four-layer structure, it uses fewer materials, making it preferable in terms of ease of recycling and other factors.

[0075] In the four-layer packaging film shown in Figure 5, the two base layers 1A may contain different polyethylenes (for example, polyethylenes with different molecular weights or physical properties). Of course, the two base layers 1A may also contain the same polyethylene resin. In the four-layer packaging film shown in Figure 5, the two coating layers 1B may be composed of different raw 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 for manufacturing packaging film> The packaging film of this embodiment is preferably manufactured by applying a coating liquid (resin solution or resin dispersion) containing one or more resins selected from the group consisting of polyurethane, polyvinyl alcohol, and polyvinylidene chloride to one side 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 the anchor coat layer, after which the above-mentioned coating liquid (resin solution or resin dispersion) is applied.

[0077] The coating solution may be water-based or organic solvent-based. That is, the coating solution typically contains one or more resins selected from the group consisting of polyurethane, polyvinyl alcohol, and polyvinylidene chloride as non-volatile components, and contains water and / or an organic solvent as volatile components. If the coating solution contains an organic solvent, the organic solvent should be appropriately selected depending on the type of resin, etc. Examples of organic solvents 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 Mitsui Chemicals, Inc.'s "Takenate," "Takelac," and "MT-Orestar" (all registered trademarks). This lineup includes both water-based (water-dispersible) and organic solvent-based options. Of course, instead of using commercially available coating solutions, a suitable polyurethane can be dissolved / dispersed in water / organic solvent to create a coating solution.

[0079] 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 provide a uniform coating layer 1B on the polyethylene-containing film, it may be better to use both water and an organic solvent.

[0080] Examples of aqueous coating solutions containing polyvinylidene chloride include latex (emulsion) containing fine particles of polyvinylidene chloride. Commercially available latex products include the Saran Latex series manufactured by Asahi Kasei Corporation. Examples of coating solutions containing polyvinylidene chloride in organic solvents include those in which polyvinylidene chloride is dissolved or dispersed in an organic solvent. Examples of usable organic solvents are as described above.

[0081] From an environmental standpoint, a water-based coating solution is preferred. However, if the coating solution 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 solution. The organic solvent that can be used at this time 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 an aqueous coating solution, the amount of the organic solvent is preferably 10 to 50% by mass of the total volatile components (sum of water and organic solvent).

[0082] For various purposes, the coating solution may contain various additive components. Examples of additive components include adhesive resins, silane coupling agents, and surfactants. In particular, it is preferable that the amount of surfactant be appropriately adjusted in order to form a uniform coating layer 1B with reduced unevenness in coating and pinholes. The amount of surfactant is preferably 0.8 to 7.5% by mass, more preferably 1.25 to 7.0% by mass, even more preferably 1.30 to 6.8% by mass, particularly preferably 1.30 to 1.80% by mass, and most preferably 1.30 to 1.55% by mass, of the total nonvolatile components of the coating solution. In other words, after the volatile components have evaporated, the coating layer 1B preferably contains 0.8 to 7.5% by mass of surfactant.

[0083] Incidentally, the presence of a surfactant in the coating solution reduces the surface resistivity of coating layer 1B. This is because the surfactant present on the surface of coating layer 1B adsorbs moisture from the air. Therefore, the surface resistivity of coating layer 1B can be used as an indicator of the surfactant content in the layer. Specifically, the surface resistivity of coating layer 1B is, for example, 1 × 10⁻⁶. 12 ~1 × 10 15 Ω, preferably 1 × 10⁻⁶ 12 ~1 × 10 14 It is Omega. Surface resistivity is measured, for example, according to the provisions of JIS K 6911.

[0084] The concentration of non-volatile 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 non-volatile components, it is easier to form a coating layer 1B of appropriate thickness.

[0085] The amount of coating applied is not particularly limited, but it is preferable to adjust it as appropriate to achieve the desired thickness of the coating layer 1B. As an example, to obtain a relatively thin coating layer 1B (approximately 0.3 to 2.0 μm) as described above, the amount of coating applied 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 Most preferably 0.4 to 1.8 g / m2 That is the case.

[0086] The packaging film of this embodiment may be manufactured by (1) first applying a coating solution containing a monomer and / or 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 method of coating is not particularly limited, and known methods can be applied. For example, methods using known devices such as air knife coaters, kiss roll coaters, metering bar coaters, gravure roll coaters, reverse roll coaters, dip coaters, and die coaters can be used.

[0088] The specific method of drying after application is not particularly limited, and known methods can be applied. For example, drying can be done using known devices such as arch dryers, straight bath dryers, tower dryers, drum dryers, and floating dryers. The drying temperature is 50 to 95°C, preferably 55 to 90°C, and more preferably 60 to 85°C, taking into consideration the heat resistance of the substrate layer 1A. 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 performed. The aging treatment is thought to strengthen the adhesion between, for example, the substrate layer 1A and the coating layer 1B. After drying, the film can be left to stand at room temperature for aging, but it is preferable to perform the aging process using an oven or the like. From the viewpoint of shortening processing time and preventing damage to the film due to heating, the aging temperature should be set considering the heat resistance and melting point of the film substrate. The aging temperature is preferably 30 to 80°C, more preferably 30 to 60°C, and even more preferably 30 to 50°C. The aging process time varies depending on the temperature conditions, but is preferably 6 to 168 hours, more preferably 12 to 120 hours, even more preferably 12 to 96 hours, and particularly preferably 12 to 72 hours.

[0090] <Applications of packaging film / packaging materials> The packaging film of this embodiment can be suitably used as a packaging film for packaging food, pharmaceuticals, daily necessities, etc.; a film for vacuum insulation panels; a sealing film for sealing electroluminescent elements, solar cells, etc., etc.

[0091] The packaging film of this embodiment can also be suitably used as a film constituting a packaging body. The packaging body is, for example, a packaging bag made of the packaging film of this embodiment, used for the purpose of packaging articles, or articles packaged in such a packaging bag. Depending on the application, only a part of the packaging body may be made of the packaging film of this embodiment, or substantially the entire packaging body may be made of the packaging film of this embodiment. The packaging can take the form of, for example, a gusseted bag or a standing pouch (pouch packaging) as described above. Gusseted bags are preferable in terms of ease of opening and appearance, as mentioned above. Pouch packaging is preferable in that it allows for ample volume to be secured in the packaging bag.

[0092] The items to be packaged are not particularly limited. Examples of items include food, pharmaceuticals, semiconductor devices, and electronic components such as organic LEDs.

[0093] Just to clarify, when constructing a package (such as a packaging bag) using the packaging film of this embodiment, in order to reliably obtain the characteristic of being "suitable for the manufacture of gusseted bags," it is preferable that the base material layer 1A is on the inner surface side and the coating layer 1B is on the outer surface side.

[0094] Food items that should be packaged include, in particular, dry items (items that may be susceptible to moisture absorption), such as baked goods (cookies, biscuits, etc.), rice crackers, rice crackers, puffed rice snacks, vegetable chips, snack foods, furikake (rice seasoning), and grain flours (wheat flour, rice flour, etc.). One or more resins selected from the group consisting of polyurethane, polyvinyl alcohol, and polyvinylidene chloride tend to be less permeable to gases such as oxygen than polyethylene. For this reason, it is preferable to use packaging bags made of the packaging film of this embodiment to package food (especially dry food as described above).

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

[0096] Although embodiments of the present invention have been described above, these are merely examples, and various other configurations can be adopted. Furthermore, the present invention is not limited to the embodiments described above, and modifications, improvements, etc., within the scope that can achieve the objectives of the present invention are included in the present invention. [Examples]

[0097] Embodiments of the present invention will be described in detail based on examples and comparative examples. The present invention is not limited to these examples. In the following, exponential notation may be indicated by the symbol "E". For example, 1.1E-06 means 1.1 × 10⁻⁶ -6 It means...

[0098] <Preparing the materials> The following materials were prepared. In the following description, "Elsmart," "TUX," and "Takerack" are registered trademarks.

[0099] (Polyethylene-containing film for forming the base layer) ·C-1 Manufactured by Mitsui Chemicals Tohcello Co., Ltd., Elsmart C-1 (thickness: 40 μm) • C-1a (thickness: 40 μm) The slip agent in C-1 above has been reduced. FC-S TUXFC-S (thickness: 50μm), manufactured by Mitsui Chemicals Tohcello Co., Ltd. ·HZ TUXHZ (thickness: 50μm), manufactured by Mitsui Chemicals Tohcello Co., Ltd. · HZR-2 TUXHZR-2 (thickness: 50μm), manufactured by Mitsui Chemicals Tohcello Co., Ltd.

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

[0101] (Coating solution for forming an anchor coat layer) A coating solution prepared by mixing Takelac A-310, Takenate A-3, and ethyl acetate, manufactured by Mitsui Chemicals, in amounts of 5.3% by mass, 0.1% by mass, and 94.6% by mass, respectively.

[0102] (Coating solution for forming a coating layer) PU This product is made by adding 2-propanol to Takelac WPB-341 (an aqueous dispersion containing polyurethane resin) manufactured by Mitsui Chemicals, Inc., to make the mass ratio of water to 2-propanol equal. PVA A coating solution prepared by mixing Kuraray's POVA 105MC with water in a mass ratio of 10:90. PVDC This is an organic solvent-based coating solution containing polyvinylidene chloride manufactured by Mitsui Chemicals MC Corporation (the polyvinylidene chloride is Saran Resin F216 manufactured by Asahi Kasei Corporation).

[0103] The non-volatile component concentrations for each coating solution were set as follows: PU: ​​9% by mass, PVA: 10% by mass, and PVDC: 5% by mass.

[0104] <Manufacturing of packaging film (formation of coating layer)> When an anchor coat layer is to be provided between the substrate layer and the coating layer, use a Meyer bar (grit #3) to apply the anchor coat layer forming solution at a rate of 0.2 g / m². 2 The amount (calculated based on non-volatile content) was applied to the surface (corona-treated side) of the substrate layer film. Then, it was left to dry for 15 seconds under conditions of 100°C to form an anchor coat layer.

[0105] The coating solution for forming the coating layer was applied to the corona-treated surface of the prepared polyethylene-containing film, or to the surface of the anchor coat layer if one was provided, using a Meyer bar. A #9 Meyer bar was used when the coating solution was PU or PVA, and a #18 Meyer bar was used when the coating solution was PVDC. The application amount was as shown in the table below (g / m²). 2 I adjusted it so that it would be as follows. The combinations of polyethylene-containing film and coating solution are as shown in the table below.

[0106] After application, drying was performed using hot air. When the coating solution was PU or PVDC, the hot air temperature was set to 100°C for 15 seconds; when the coating solution was PVA, the hot air temperature was set to 70°C for 15 seconds.

[0107] After drying, aging treatment was performed at 40°C for 24 hours if the coating solution was PU or PVA, and at 40°C for 48 hours if the coating solution was PVDC. The packaging film was manufactured in the manner described above.

[0108] <Measurement of various numerical values> (Glass transition temperature (Tgs, Tgc), melting point (Tm)) Approximately 3.0 mg each of the coating layer and the base layer were taken from the packaging film and used as measurement samples. The glass transition temperature and melting point were determined by DSC measurement of each sample. Details of the DSC measurement are as follows. • Measurement temperature steps: (i) Hold at -50°C for 10 minutes → (ii) Increase temperature and hold at 250°C for 10 minutes → (iii) Decrease temperature and hold at -50°C for 10 minutes → (iv) Increase temperature to 250°C • Heating rate and cooling rate between each step (i) to (iv): 5°C / min • Measurement atmosphere: Nitrogen gas

[0109] Based on the DSC curve obtained during the heating step (2nd run) between (iii) and (iv) above, the glass transition temperature and melting point were determined. For the glass transition temperature, the extrapolation glass transition onset temperature was adopted. For the melting point, the peak top temperature of the melting peak was used.

[0110] (SRz and SRku) The three-dimensional surface properties of the coating layer surface and the corona-treated surface of the polyethylene-containing film (before coating layer formation) were measured using the SE-3500 three-dimensional surface roughness measuring instrument from Kosaka Laboratory Co., Ltd. The specific measurement conditions (equipment settings, etc.) are as follows. The SRz and SRku values ​​were then determined by analyzing the data obtained from the measurements using software.

[0111] ·Measurement length: MD direction; 400μm, TD direction; 1000μm • Number of measurement lines: TD direction lines; 201 • Measurement pitch: MD direction; 0.5 μm, TD direction; 2 μm ·Z measurement magnification: 5000 • X feed rate: 0.2 mm / s • Low-frequency cut: 0.25mm • High-frequency cut: R+W • Leveling: Least Squares Method • 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) The measurement was performed according to the following procedure. (1) Two sheets of each polyethylene-containing film, cut to a size of 50 mm x 75 mm (hereinafter referred to as film 1 and film 2), were prepared. (2) Film 1 was fixed to a plate (hereinafter referred to as the inclined plate) whose inclination angle could be freely adjusted. (3) A rectangular component with a brass base (base dimensions 41mm x 26mm) was fixed to film 2. A weight was then attached to the component so that the mass on film 2 was 150g. (4) Film 2 was placed 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 then calculated from the angle θ at which the upper film 2 began to slide (static friction coefficient = tanθ).

[0113] One side of the polyethylene-containing film used in this study was corona-treated. Therefore, 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 at a temperature of 23°C and a humidity of 50%RH. Afterward, the surface resistivity was measured using an Advantest digital ultra-high resistance / micro-current meter (R8340A) and a resistivity chamber (R12704). The measurement conditions were: applied voltage 560V, application time 30 seconds, temperature 23°C, and humidity 50%RH.

[0115] (Thickness of the coating layer) The thickness of the coating layer was measured using a Filmmetrics F20-UV film thickness analyzer (light source: halogen, measurement spot diameter: 1.5 mm). In this study, the thickness of a single document was measured at three arbitrary locations. The average of these three thicknesses was then used as the thickness of the coating layer.

[0116] (Application amount (calculated based on non-volatile components)) • If the coating liquid is PU The coating layer on the packaging film was wiped off using DMF (dimethylformamide). The amount of coating applied (calculated in terms of non-volatile content) was then calculated from the change in mass before and after wiping. • If the coating solution is PVA The packaging film was immersed in boiling water to dissolve the coating layer on the film. The amount of coating applied (calculated in terms of non-volatile content) was then calculated from the change in mass before and after immersion. • If the coating solution is PVDC The calculation was based on the intensity of the Cl-derived peak obtained by X-ray fluorescence analysis. A calibration curve obtained using a substance with a known Cl content was utilized.

[0117] The various pieces of information mentioned above are 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 indicates whether or not an anchor coat layer is present. The comparative films all lack a coating layer. Therefore, there are no entries for the comparative films in Table 2. In Tables 1 and 2, a "-" in the surface resistivity column indicates that the surface resistivity was not measured. In Table 2, a "-" in the "Surfactant Percentage" column indicates that the coating solution did not contain a surfactant. In Table 2, a "-" in the melting point Tm column 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 performed using the following procedure. (1) Two films were prepared for each example or each comparative example. (2) (i) Two films from each example were stacked so that the coated layer surfaces were in contact with each other. Or, (ii) Two samples from each comparative example were stacked so that the corona-treated surfaces were in contact with each other. At this time, the MD / TD directions of the two samples were aligned. (3) The two superimposed samples were heated using a sealing iron under the following conditions: temperature 70°C, pressure 2.0 kgf, sealing time 60 seconds, and sealing width 10 mm. This resulted in samples in which the two samples were intentionally blocked. (4) After heating, the samples were allowed to cool naturally at room temperature. (5) The sample was reinforced by applying commercially available adhesive tape to both the front and back surfaces (this is because if the blocking strength is too strong, the sample will stretch in the tensile test in (6) below, making it impossible to accurately measure the blocking strength). (6) The sample, cooled to room temperature, was placed in a tensile testing machine and pulled in the MD direction of the base film at a tensile speed of 5 mm / min. The load until the sample separated into individual sheets was recorded.

[0121] The maximum recorded load is listed in the "BL Resistance Strength" column of the table below. A smaller value indicates better blocking resistance.

[0122] (Suitability for manufacturing gusseted bags, etc.: Evaluation of heat-sealing properties of the heat-sealed portion on the back) In the following, we evaluated the "heat-sealability of the back heat-seal portion" when manufacturing gusseted bags, etc., by assessing the resistance of heat fusion 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 each comparative example. (2) (i) Two samples from each example were stacked so that the surfaces of the coating layers were in contact with each other. Or, (ii) Two samples from each comparative example were stacked so that the corona-treated surfaces of the films used as the substrate layer were in contact with each other. At this time, the MD / TD directions of the two samples were aligned. (3) The two stacked samples were heated using a sealing iron under the following conditions: temperature 140°C, pressure 1.5 kgf, sealing time 1.0 second, and sealing width 10 mm. (4) After heating, the samples were allowed to cool naturally at room temperature.

[0124] The condition of the samples cooled to room temperature, and the ease of separating the two samples, were evaluated on a three-point scale as follows. ◎(Excellent): No thermal fusion was observed between the two samples. ○ (Good): Slight thermal fusion is observed between the two samples, but they can be easily separated by hand. × (Bad): The two samples are clearly heat-fused together. When attempting to separate them, the substrate layer stretches.

[0125] Incidentally, in (2)(i) above, the same procedure as in (1) to (4) above was followed, except that the two samples of each example were stacked so that the surfaces (the sides opposite to the coating layer) of the polyethylene-containing film used as the base layer were in contact with each other. As a result, in all examples, the polyethylene melted sufficiently and a heat-sealed portion was formed.

[0126] (Oxygen permeability) Using a Mokon OX-TRAN2 / 21 instrument, the oxygen permeability of packaging films was measured in accordance with JIS K 7126 under the conditions of (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 contained polyurethane, an aluminum mask was used to reduce the measurement area to 1 / 10 or 1 / 50 and measure the oxygen permeability. The obtained oxygen permeability value (raw data) was then multiplied by 10 or 50 to obtain the oxygen permeability value. This is because polyurethane is more permeable to oxygen 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. For the performance evaluation, only one of the following values ​​is shown for oxygen permeability: the value measured under conditions of 23±2°C and 90±1.0%RH, or the value measured under conditions of 23±2°C and 50±1.0%RH.

[0128] [Table 3]

[0129] In each example, the blocking resistance was improved by providing a coating layer containing polyurethane polyvinyl alcohol or polyvinylidene chloride on one side of the base layer. For example, the blocking resistance of the films in 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] Furthermore, in each example, by providing a coating layer containing polyurethane polyvinyl alcohol or polyvinylidene chloride on one side of the base material layer, the suitability for manufacturing gusseted bags and the like was improved.

[0131] Furthermore, in each example, the oxygen permeability was reduced by providing a coating layer containing polyurethane polyvinyl alcohol or polyvinylidene chloride on one side of the substrate layer (see the examples and comparative examples where the substrate layer is common).

[0132] A more detailed analysis of the examples reveals the following, for example: In Examples 3 to 6, the base film and coating solution were the same, but the thickness of the coating layer differed. In Examples 5 and 6, where the coating layer thickness was relatively large, the blocking resistance strength was relatively high. On the other hand, in Examples 3 and 4, where the coating layer thickness was relatively small, the blocking resistance strength was relatively low. Common sense might suggest that the thicker the coating layer, the lower the blocking resistance. However, Examples 3-6 showed that a "moderately thin" coating layer resulted in lower blocking resistance (i.e., better blocking resistance). [Explanation of symbols]

[0133] 1 film 1A Base material layer 1B Coating layer 10. Rear heat seal section 15. Bottom heat seal section

Claims

1. A substrate layer containing polyethylene (excluding polyethylene resin stretched films in which the degree of crosslinking decreases inward in the thickness direction of the film), A coating layer comprising one or more resins selected from the group consisting of polyvinyl alcohol and polyvinylidene chloride, without containing polyurethane, and provided in contact with one side of the substrate layer or via an anchor coat layer, A packaging film comprising the above, wherein the thickness of the coating layer is less than the thickness of the base material layer, The oxygen permeability measured under conditions of 23±2°C and 90±1.0% RH is 1.0 × 10⁻¹⁰. ５ mL / (m ２ 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 × 10⁻¹⁰ MPa (day·MPa) and / or less than 1.0 × 10⁻¹⁰ MPa (day·MPa). ５ mL / (m ２ (day MPa) is less than, The static friction coefficient between the two surfaces of the aforementioned base material layer is 0.08 to 2.

50. The thickness of the substrate layer is 10 to 150 μm. The polyethylene includes linear low-density polyethylene. The aforementioned coating layer is a single layer, The coating layer is present on the outermost surface of the packaging film. The ten-point average roughness SRz of the surface of the coating layer, obtained by three-dimensional measurement, is 0.50 μm or more. The aforementioned substrate layer is a single-layer packaging film (however, excluding laminates comprising a substrate made of a heat-sealable plastic film, a polyurethane layer laminated on the substrate, and a metal vapor-deposited layer laminated on the polyurethane layer, wherein the polyurethane layer is obtained by applying and drying a coating liquid containing a polyurethane dispersion containing a polyurethane resin obtained by reacting a polyisocyanate component containing xylylene diisocyanate and / or hydrogenated xylylene diisocyanate with a polyol component containing a diol having 2 to 6 carbon atoms and an active hydrogen group-containing compound containing a hydrophilic group, and a chain extender, onto the substrate).

2. A substrate layer containing polyethylene (excluding polyethylene resin stretched films in which the degree of crosslinking decreases inward in the thickness direction of the film), A coating layer comprising one or more resins selected from the group consisting of polyvinyl alcohol and polyvinylidene chloride, without containing polyurethane, and provided in contact with one side of the substrate layer or via an anchor coat layer, A packaging film comprising the above, wherein the thickness of the coating layer is less than the thickness of the base material layer, The oxygen permeability measured under conditions of 23±2°C and 90±1.0% RH is 1.0 × 10⁻¹⁰. ５ mL / (m ２ 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 × 10⁻¹⁰ MPa (day·MPa) and / or less than 1.0 × 10⁻¹⁰ MPa (day·MPa). ５ mL / (m ２ (day MPa) is less than, The static friction coefficient between the two surfaces of the aforementioned base material layer is 0.08 to 2.

50. The thickness of the substrate layer is 10 to 150 μm. The polyethylene includes linear low-density polyethylene. The aforementioned coating layer is a single layer, The coating layer is present on the outermost surface of the packaging film. The kurtosis SRku obtained by three-dimensional measurement of the surface of the coating layer is 25 or more. The aforementioned substrate layer is a single-layer packaging film (however, excluding laminates comprising a substrate made of a heat-sealable plastic film, a polyurethane layer laminated on the substrate, and a metal vapor-deposited layer laminated on the polyurethane layer, wherein the polyurethane layer is obtained by applying and drying a coating liquid containing a polyurethane dispersion containing a polyurethane resin obtained by reacting a polyisocyanate component containing xylylene diisocyanate and / or hydrogenated xylylene diisocyanate with a polyol component containing a diol having 2 to 6 carbon atoms and an active hydrogen group-containing compound containing a hydrophilic group, and a chain extender, onto the substrate).

3. A substrate layer containing polyethylene (excluding polyethylene resin stretched films in which the degree of crosslinking decreases inward in the thickness direction of the film), A coating layer comprising one or more resins selected from the group consisting of polyurethane, polyvinyl alcohol, and polyvinylidene chloride, and provided in contact with one side of the substrate layer or provided via an anchor coat layer, A packaging film comprising the above, wherein the thickness of the coating layer is less than the thickness of the base material layer, The oxygen permeability measured under the conditions of a temperature of 23 ± 2°C and a humidity of 90 ± 1.0% RH is less than 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), The static friction coefficient between the two surfaces of the aforementioned base material layer is 0.08 to 2.

50. The thickness of the substrate layer is 10 to 150 μm. The polyethylene includes linear low-density polyethylene. The aforementioned coating layer is a single layer, The coating layer is present on the outermost surface of the packaging film. The ten-point average roughness SRz of the surface of the coating layer, obtained by three-dimensional measurement, is 0.50 μm or more. The surface resistivity of the coating layer is 1 × 10⁻⁶ １２ ~1 x 10 １５ Packaging film of Ω (excluding laminates comprising a base material made of a heat-sealable plastic film, a polyurethane layer laminated on the base material, and a metal vapor-deposited layer laminated on the polyurethane layer, wherein the polyurethane layer is obtained by applying and drying a coating liquid containing a polyurethane dispersion containing a polyurethane resin obtained by reacting a polyisocyanate component containing xylylene diisocyanate and / or hydrogenated xylylene diisocyanate with a polyol component containing a diol having 2 to 6 carbon atoms and an active hydrogen group-containing compound containing a hydrophilic group, and a chain extender, onto the base material).

4. A substrate layer containing polyethylene (excluding polyethylene resin stretched films in which the degree of crosslinking decreases inward in the thickness direction of the film), A coating layer comprising one or more resins selected from the group consisting of polyurethane, polyvinyl alcohol, and polyvinylidene chloride, and provided in contact with one side of the substrate layer or provided via an anchor coat layer, A packaging film comprising the above, wherein the thickness of the coating layer is less than the thickness of the base material layer, The oxygen permeability measured under conditions of 23±2°C and 90±1.0% RH is 1.0 × 10⁻¹⁰. ５ mL / (m ２ 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 × 10⁻¹⁰ MPa (day·MPa) and / or less than 1.0 × 10⁻¹⁰ MPa (day·MPa). ５ mL / (m ２ (day MPa) is less than, The static friction coefficient between the two surfaces of the aforementioned base material layer is 0.08 to 2.

50. The thickness of the substrate layer is 10 to 150 μm. The polyethylene includes linear low-density polyethylene. The aforementioned coating layer is a single layer, The coating layer is present on the outermost surface of the packaging film. The kurtosis SRku obtained by three-dimensional measurement of the surface of the coating layer is 25 or more. The surface resistivity of the coating layer is 1 × 10⁻⁶ １２ ~1 x 10 １５ Packaging film of Ω (excluding laminates comprising a base material made of a heat-sealable plastic film, a polyurethane layer laminated on the base material, and a metal vapor-deposited layer laminated on the polyurethane layer, wherein the polyurethane layer is obtained by applying and drying a coating liquid containing a polyurethane dispersion containing a polyurethane resin obtained by reacting a polyisocyanate component containing xylylene diisocyanate and / or hydrogenated xylylene diisocyanate with a polyol component containing a diol having 2 to 6 carbon atoms and an active hydrogen group-containing compound containing a hydrophilic group, and a chain extender, onto the base material).

5. A packaging film according to any one of claims 1 to 4, The packaging film having a coating layer thickness of 0.3 to 2.0 μm.

6. A packaging film according to any one of claims 1 to 5, When the glass transition temperature of the coating layer is Tgc and the glass transition temperature of the substrate layer is Tgs, A packaging film with a Tgc value of -25 to 120°C and a Tgc-Tgs value of 90 to 245°C.

7. The packaging film according to claim 6, TGS refers to packaging film with a temperature range of -130 to -120°C.

8. A packaging film according to any one of claims 1 to 7, The coating layer is a packaging film that has no melting point or has a melting point of 120 to 230°C.

9. A packaging film according to any one of claims 1 to 8, The aforementioned coating layer contains a surfactant, A packaging film in which the proportion of the surfactant in the coating layer is 0.8 to 7.5% by mass.

10. A package made of a packaging film according to any one of claims 1 to 9.

11. The packaging according to claim 10, A packaging body having the aforementioned coating layer on its outer surface.

Images