Resin film and packaging

Abstract

To provide a resin film having a Japanese paper-like appearance.SOLUTION: A resin film has surface reflection roughness of 2.0 or more, the surface reflection roughness stipulated as an average of residual standard deviation σ to a regression line, of surface reflection light intensity.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resin film and a packaging body. [Background technology]

[0002] Traditionally, wrapping paper made from paper pulp has been used to wrap boxes containing products at department stores, supermarkets, etc. However, because wrapping paper has low water resistance, the wrapping paper can tear due to condensation or the like during storage or transportation of the wrapped box.

[0003] On the other hand, so-called stone paper is known as a packaging material with excellent water resistance (see, for example, Patent Document 1). Stone paper is a film made by forming a resin composition in which an inorganic filler such as calcium carbonate is added to a resin material such as polyethylene or polypropylene. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 07-102096 Summary of the Invention [Problem to be solved by the invention]

[0005] Various types of wrapping paper made from pulp, such as high-quality paper and recycled paper, are used, but depending on the application, a luxurious feel may be required. For example, a resin film with an appearance similar to that of Japanese paper is useful as a luxurious wrapping paper. However, while conventional stone paper has an appearance similar to that of paper, it cannot be said to have such a Japanese paper-like appearance.

[0006] An object of the present invention is to provide a resin film having an appearance similar to that of Japanese paper. [Means for solving the problem]

[0007] The first resin film of the present invention is a resin film having a surface reflection roughness of 2.0 or more, which is defined as the average value of the residual standard deviation σ of the surface reflected light intensity relative to a regression line. The second resin film of the present invention is a resin film having an average thickness of 25.0 μm or more and a thickness ratio defined as the ratio between the maximum thickness and the minimum thickness of 2.0 or more. [Effects of the Invention]

[0008] According to the present invention, a resin film having an appearance similar to that of Japanese paper can be provided. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a graph showing the surface reflected light intensity of a resin film. [Figure 2] FIG. 2 is a photograph showing the appearance of the stretched laminate of Example 1. [Figure 3] FIG. 3 is a photograph showing the appearance of the laminate of Comparative Example 3. [Figure 4] FIG. 4 is a scanning electron microscope image of a cross section of the stretched laminate of Example 1. [Figure 5] FIG. 5 is a scanning electron microscope image of a cross section of the stretched laminate of Example 1. [Figure 6] FIG. 6 is a scanning electron microscope image of a cross section of the stretched laminate of Example 1. [Figure 7] FIG. 7 is a scanning electron microscope image of a cross section of the stretched laminate of Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Resin film] The first resin film of the present invention has a surface reflection roughness of 2.0 or more, as described below. Since the first resin film has a surface reflection roughness of 2.0 or more, the first resin film has uneven reflected light intensity, and therefore has a non-uniform appearance resembling that of Japanese paper. Therefore, the first resin film can be suitably used as a substitute for a paper substrate.

[0011] The second resin film of the present invention has an average thickness of 25.0 μm or more, and a thickness ratio defined as the ratio of the maximum thickness to the minimum thickness of 2.0 or more. The second resin film has a large variation in thickness, resulting in a non-uniform appearance resembling that of Japanese paper. Therefore, the second resin film can also be suitably used as a substitute for a paper substrate.

[0012] Hereinafter, when simply referred to as a "resin film", it may refer to either the first resin film or the second resin film of the present invention.

[0013] In the present invention, the surface reflection roughness is a numerical value that represents the unevenness of the intensity (brightness) of the reflected light when the film to be measured is irradiated with light. The surface reflection roughness is a larger value when the unevenness is large, and is a smaller value when the unevenness is small.

[0014] (Method for measuring surface reflection roughness) Specifically, the surface reflective roughness of the film is measured as follows. The film to be measured is attached to a black acrylic resin plate using tape. An LED light source (specifically, a Yamada Lighting Co., Ltd. Z-PRO80II) with an average color rendering index (Ra) of 90 or higher in accordance with JIS Z 8726:1990 is used to illuminate the film at a 5° incident angle (5° relative to the normal to the film surface). A digital camera (specifically, a Nikon Corporation D5600 digital camera) is placed at a 5° reflection angle (-5° relative to the normal to the film surface) to take a photograph of the film surface at this time. The light intensity of the LED light source is set to 800 Lux at the sample surface. The distance between the LED light source and the film surface is 1 m, and the distance between the digital camera and the film surface is 0.5 m. The above photographs are preferably taken in a darkroom environment.

[0015] When taking the above photograph, the sensitivity and aperture of the digital camera, which affect the brightness of the photograph, are set so that the average value of the brightness numerical data (8 bits, 256 levels) below falls within the range of 20 to 200.

[0016] Using the image processing software "ImageJ" (manufactured by the National Institutes of Health, USA), each pixel of the obtained image is converted into numerical data expressed as a brightness value in 256 gradations, and a data matrix consisting of the brightness numerical data for each pixel is obtained for data 1000 pixels long each. Specifically, a photograph is taken at a resolution of about 20 to 100 μm, preferably about 20 to 30 μm, per pixel, and the above data matrix is ​​obtained for an area of ​​about 2 to 10 cm square, preferably about 2 to 3 cm square, on the film.

[0017] For the data matrix, several locations (e.g., three locations) are randomly selected in the vertical direction (e.g., longitudinal direction, MD direction) of the film, and several locations (e.g., three locations) are randomly selected in the horizontal direction (e.g., transverse direction, TD direction) of the film, and the horizontal axis is plotted as pixels and the vertical axis is plotted as brightness values ​​in 256 levels, to obtain several graphs showing the brightness distribution (see Figure 1).

[0018] A linear fit is performed on the numerical data of the graph using the least squares method to obtain a regression line. The difference between the numerical data and the regression line is calculated for each plotted pixel. The standard deviation σ of the difference (the residual standard deviation σ for the regression line) is calculated. The average value of the standard deviation σ is calculated from the graph obtained for each of several randomly selected points in the data matrix, and this average value is referred to as the "surface reflection roughness" in this invention.

[0019] The above method obtains the longitudinal and lateral surface reflection roughness of the film to be measured. The first resin film is sufficient if at least one of the longitudinal and lateral surface reflection roughnesses is 2.0 or greater, but it is preferable that both are 2.0 or greater. Furthermore, the first resin film is sufficient if the surface reflection roughness measured on at least one side is equal to or greater than the above-mentioned value.

[0020] The surface reflection roughness of the first resin film is preferably 3.0 or more, more preferably 4.0 or more, and preferably 12.0 or less, more preferably 9.0 or less, and even more preferably 8.0 or less, from the viewpoint of obtaining an appearance closer to that of Japanese paper. It is preferable that the second resin film also meets such requirements for surface reflection roughness.

[0021] In one embodiment, the resin film contains white inorganic particles and a resin material. Examples of white inorganic particles include calcium salts such as calcium carbonate and calcium sulfate, barium salts such as barium sulfate, metal oxides such as zinc oxide, titanium dioxide and silicon dioxide, kaolin, and talc. Among these, calcium salts are preferred, calcium carbonate is more preferred, and heavy calcium carbonate is even more preferred, from the viewpoint of obtaining a resin film having an appearance closer to that of Japanese paper. The resin film may contain one or more types of white inorganic particles.

[0022] The average particle size of the white inorganic particles is preferably 0.1 μm to 50 μm, more preferably 0.3 μm to 40 μm, even more preferably 0.5 μm to 35 μm, and particularly preferably 0.5 μm to 15 μm, thereby obtaining a resin film with a high surface reflection roughness and a high film thickness ratio, for example.

[0023] The maximum particle size of the white inorganic particles is preferably 70 μm or less, more preferably 60 μm or less, and even more preferably 50 μm or less. From the viewpoint of film manufacturability, the maximum particle size of the white inorganic particles is preferably 70% or less, more preferably 60% or less, and even more preferably 50% or less of the average film thickness of the resin film.

[0024] The average particle size and maximum particle size are measured by electron microscopy. Specifically, in a cross-sectional image of a resin film photographed using a scanning electron microscope, the arithmetic mean of the major axis diameters of 100 white inorganic particles randomly selected according to the following criteria is defined as the average particle size, and the maximum value of these major axis diameters is defined as the maximum particle size. The average particle size is a value obtained by averaging the major axis diameters of white inorganic particles contained in the resin film, which are presumed to affect film thickness unevenness and reflected light intensity unevenness, and have a major axis diameter of 0.05 μm or more. The major axis diameter refers to the maximum distance between two parallel lines when a particle image in the cross-sectional image is sandwiched between the parallel lines.

[0025] The content of the white inorganic particles in the resin film is preferably 40% by mass or more, more preferably more than 50% by mass, even more preferably 51% by mass to 70% by mass, even more preferably 52% by mass to 65% by mass, and particularly preferably 52% by mass to 60% by mass. If the content of the white inorganic particles is equal to or greater than the lower limit, the thickness of the layer containing a large amount of white inorganic particles becomes non-uniform during stretching, and therefore thickness unevenness tends to be favorably formed.

[0026] Resin films containing more than 50% by mass of white inorganic particles have a low carbon dioxide emission rate during the manufacturing process and incineration process, and therefore have a low environmental impact, unlike plastic materials that use large amounts of fossil resources. Therefore, the resin film can be disposed of as combustible waste. When the content of white inorganic particles is equal to or less than the upper limit, the occurrence of breakage and other problems during the stretching process during resin film manufacturing can be suppressed. The content of the above white inorganic particles can be determined in accordance with JIS K7250-1:2006 (ISO 3451-1:1997) Plastics - Determination of ash content - Part 1: General rules or by measuring the weight after incineration by TG-DTA.

[0027] In one embodiment, in a cross-sectional image of the resin film, voids are present around at least some of the white inorganic particles. Note that it is sufficient that voids are present around a portion of the white inorganic particles, and voids do not have to be present around the entire periphery. In this embodiment, it is sufficient that the voids are present in at least one cross section obtained by cutting the resin film.

[0028] The cross-sectional image is obtained, for example, by a scanning electron microscope (SEM). For example, in a cross-section obtained by cutting a white portion of a resin film in a top-view image by SEM along the transverse direction (TD) of the resin film, voids tend to be present at least in part around the white inorganic particles. On the other hand, in a cross-section obtained by cutting the white portion along the longitudinal direction (MD) of the resin film or in a cross-section of a transparent portion of the resin film, the voids tend to be absent or few. In such a resin film, the presence of voids is anisotropic, and this anisotropy is thought to contribute to the formation of a Japanese paper-like appearance. Non-uniform voids can be formed by a stretching treatment described below.

[0029] Examples of resin materials contained in the resin film include polyolefins such as polyethylene and polypropylene, polystyrene, polyester, polyurethane, and polyvinyl chloride, with polyolefins being preferred and polyethylene and polypropylene being more preferred.

[0030] In the present invention, polyethylene refers to a polymer in which the content of ethylene-derived structural units is 50 mol% or more of all repeating structural units. In this polymer, the content of ethylene-derived structural units is preferably 70 mol% or more, more preferably 80 mol% or more, and even more preferably 90 mol% or more. The content is measured by nuclear magnetic resonance (NMR) spectroscopy.

[0031] In the present invention, polypropylene refers to a polymer in which the content of propylene-derived structural units in all repeating structural units is 50 mol% or more. In this polymer, the content of propylene-derived structural units is preferably 70 mol% or more, more preferably 80 mol% or more, and even more preferably 90 mol% or more. The content is measured by NMR.

[0032] Examples of polyethylene include ethylene homopolymers and copolymers of ethylene with other monomers. Examples of other monomers include α-olefins having 3 to 20 carbon atoms, vinyl acetate, (meth)acrylic acid, and (meth)acrylic acid esters. Examples of α-olefins having 3 to 20 carbon atoms include propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene, 3-methyl-1-butene, 4-methyl-1-pentene, and 6-methyl-1-heptene. Examples of (meth)acrylic acid esters include alkyl (meth)acrylates such as methyl (meth)acrylate and ethyl (meth)acrylate.

[0033] Examples of the copolymer include a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms, a copolymer of ethylene and at least one selected from vinyl acetate, (meth)acrylic acid, and (meth)acrylic acid esters, and a copolymer of ethylene, an α-olefin having 3 to 20 carbon atoms, and at least one selected from vinyl acetate, (meth)acrylic acid, and (meth)acrylic acid esters.

[0034] Examples of polyethylene include high-density polyethylene (HDPE), medium-density polyethylene (MDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), very low-density polyethylene (VLDPE), ethylene-vinyl acetate copolymer, ethylene-(meth)acrylic acid ester copolymer, and ethylene-(meth)acrylic acid copolymer.

[0035] The density of the high density polyethylene is preferably 0.945 g / cm 3 The upper limit of the density of high density polyethylene is, for example, 0.965 g / cm 3 is. The density of the medium density polyethylene is preferably 0.925 g / cm 3 Exceeds 0.945g / cm 3 The following is the result.

[0036] The density of the low density polyethylene is preferably 0.900 g / cm 3 Exceeds 0.925g / cm 3 Low-density polyethylene is usually polyethylene obtained by polymerizing ethylene using a high-pressure polymerization method.

[0037] The density of the linear low density polyethylene is preferably 0.900 g / cm 3 Exceeds 0.925g / cm 3 Linear low-density polyethylene is typically obtained by polymerizing ethylene and a small amount of α-olefins using a low-pressure polymerization method (e.g., polymerization using a Ziegler-Natta catalyst or a metallocene catalyst).

[0038] The density of the ultra-low density polyethylene is preferably 0.900 g / cm 3 The lower limit of the density of the ultra-low density polyethylene is, for example, 0.860 g / cm 3 is. The density of polyethylene is measured in accordance with JIS K7112 (1999).

[0039] Examples of polypropylene include propylene homopolymers and copolymers of propylene with other monomers. Examples of other monomers include ethylene, α-olefins having 4 to 20 carbon atoms, vinyl acetate, (meth)acrylic acid, and (meth)acrylic acid esters. Examples of α-olefins having 4 to 20 carbon atoms include 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene, 3-methyl-1-butene, 4-methyl-1-pentene, and 6-methyl-1-heptene. Examples of (meth)acrylic acid esters include alkyl (meth)acrylates such as methyl (meth)acrylate and ethyl (meth)acrylate.

[0040] Examples of the copolymer include a copolymer of propylene and at least one selected from ethylene and an α-olefin having 4 to 20 carbon atoms; a copolymer of propylene and at least one selected from vinyl acetate, (meth)acrylic acid, and a (meth)acrylic acid ester; and a copolymer of propylene and ethylene and / or an α-olefin having 4 to 20 carbon atoms and at least one selected from vinyl acetate, (meth)acrylic acid, and a (meth)acrylic acid ester.

[0041] The melt flow rate (MFR) of the polyolefin is preferably 0.1 g / 10 min to 100 g / 10 min, more preferably 0.5 g / 10 min to 30 g / 10 min, and even more preferably 1 g / 10 min to 10 g / 10 min. The MFR is measured by Method A according to JIS K7210-1995, for example, at a temperature of 190°C for polyethylene and at a temperature of 230°C for polypropylene under a load of 2.16 kg. If the MFR of the polyolefin is 0.1 g / 10 min or more, the extrusion load during molding can be reduced. If the MFR of the polyolefin is 100 g / 10 min or less, the mechanical strength of the polyolefin-containing layer can be increased.

[0042] The polyolefin may be a polyolefin derived from a fossil fuel or a polyolefin derived from biomass. Biomass is an organic compound photosynthesized from carbon dioxide and water, and by utilizing this organic compound, it is converted back into carbon dioxide and water, making it a so-called carbon-neutral renewable material. Because biomass-derived polyolefin is a carbon-neutral material, resin films and packaging materials obtained from the films can contribute to resource conservation and carbon dioxide reduction, thereby reducing the environmental impact.

[0043] Biomass polyolefin is a polymer of raw material monomers containing biomass-derived olefins (e.g., ethylene), and biomass polyethylene is preferred. Since biomass-derived olefins are used as raw material monomers, the resulting polyolefins are derived from biomass. One or more types of biomass polyolefins can be used.

[0044] The raw material monomers for biomass polyolefins do not have to contain 100% by mass of biomass-derived olefins. The raw material monomers for biomass polyolefins may further contain other monomers, such as fossil fuel-derived ethylene and / or fossil fuel-derived α-olefins having from 3 to 20 carbon atoms. Specific examples of other monomers, such as α-olefins having from 3 to 20 carbon atoms, are as described above.

[0045] For example, the content of biomass-derived olefins in the raw material monomers is preferably 50% by mass or more, more preferably 80% by mass or more. The raw material monomers may also contain olefins derived from fossil fuels. Even in such cases, the resulting polymer is called a biomass polyolefin.

[0046] For example, biomass-derived ethylene can be produced using biomass-derived ethanol as a raw material. In particular, it is preferable to use biomass-derived fermented ethanol obtained from plant raw materials. Examples of plant raw materials include conventionally known plants such as corn, sugarcane, beet, and manioc.

[0047] Fermented ethanol derived from biomass refers to ethanol produced and purified by contacting a culture solution containing a carbon source obtained from plant raw materials with an ethanol-producing microorganism or a product derived from the disrupted microorganism. Ethanol can be purified from the culture solution by conventional methods such as distillation, membrane separation, and extraction. Examples of methods include adding benzene, cyclohexane, etc., and removing water by azeotropy or membrane separation. The resin film can contain one or more types of resin materials.

[0048] The content of the resin material in the resin film is preferably 60% by mass or less, more preferably less than 50% by mass, even more preferably 30% by mass to 49% by mass, even more preferably 35% by mass to 48% by mass, and particularly preferably 40% by mass to 48% by mass. A resin film having a content of the resin material in the above range has excellent waste disposal properties because the amount of resin material used is small.

[0049] The resin film may further contain additives other than the white inorganic particles, such as a heat stabilizer, an ultraviolet absorber, an antioxidant, a coupling agent, a lubricant, a dispersant, and an antistatic agent. The resin film may contain one or more additives.

[0050] The total light transmittance of the resin film is preferably 80% or less, more preferably 75% or less, and even more preferably 70% or less. In one embodiment, the lower limit of the total light transmittance may be 1%. The total light transmittance of the resin film is measured in accordance with JIS K7361-1.

[0051] The haze value of the resin film is preferably 80.0% or more, more preferably 90.0% or more, even more preferably 95.0% or more, and still more preferably 97.0% or more. The haze value of the resin film is measured in accordance with JIS K7136.

[0052] Resin films have excellent water resistance. In one embodiment, resin films have a significantly lower moisture content than paper, and tend to exhibit smaller dimensional changes even when they absorb a small amount of water. For this reason, resin films have better water resistance than paper.

[0053] The average thickness of the second resin film is 25.0 μm or more, preferably 30.0 μm or more and 200.0 μm or less, more preferably 40.0 μm or more and 120.0 μm or less, and even more preferably 40.0 μm or more and 70.0 μm or less. The average thickness of the first resin film is also preferably within these ranges, but may be, for example, 20.0 μm or more. When the average thickness of the resin film is 25.0 μm or more, the strength of the resin film can be improved. When the average thickness of the resin film is 200.0 μm or less, the processability of the resin film can be improved.

[0054] The thickness ratio of the second resin film, defined as the ratio of the maximum thickness to the minimum thickness, is 2.0 or more, preferably 2.5 to 10.0, and more preferably 3.0 to 8.0. The thickness ratio of the first resin film is also preferably within these ranges. Such a resin film has a large surface irregularity and therefore exhibits an appearance closer to that of Japanese paper. In the present invention, the average film thickness, maximum film thickness and minimum film thickness of the resin film are measured with a step-type film thickness meter, specifically, by the method described in the Examples section.

[0055] <Resin film composition> (White inorganic particle containing layer) In one embodiment, the resin film includes a layer containing white inorganic particles and a resin material, the layer having a white inorganic particle content of more than 50 mass % (hereinafter also referred to as a "white inorganic particle-containing layer"). Specific examples and preferred examples of the white inorganic particles and the resin material are as described above.

[0056] In one embodiment, the white inorganic particles are dispersed in the resin material (particularly polyolefin) that constitutes the white inorganic particle-containing layer to such an extent that they do not aggregate.

[0057] The content of the white inorganic particles in the white inorganic particle-containing layer is more than 50% by mass, preferably from 51 to 80% by mass, more preferably from 52 to 70% by mass, and even more preferably from 52 to 65% by mass. If the content of the white inorganic particles is equal to or greater than the lower limit, the thickness of the white inorganic particle-containing layer becomes non-uniform during stretching, and therefore unevenness in thickness and reflected light intensity tends to be favorably formed.

[0058] In one embodiment, the resin material constituting the white inorganic particle-containing layer includes polyethylene. The resin film of this embodiment tends to have better repeated stretchability. In one embodiment, the content of polyethylene relative to the total amount of the resin material constituting the white inorganic particle-containing layer is 50% by mass or more, preferably 80% by mass or more, and more preferably 90% by mass or more.

[0059] In one embodiment, the resin material constituting the white inorganic particle-containing layer includes polypropylene. The resin film of this embodiment is suitable for applications requiring heat resistance, such as packaging applications such as pillow packaging materials requiring heat sealing, as described below, and also tends to have excellent repeated stretchability, tearability, and therefore ease of opening. In one embodiment, the content of polypropylene relative to the total amount of the resin material constituting the white inorganic particle-containing layer is 50% by mass or more, preferably 60% by mass or more, and more preferably 70% by mass or more.

[0060] The content of the resin material in the white inorganic particle-containing layer is preferably less than 50% by mass, more preferably 20% by mass to 49% by mass, even more preferably 30% by mass to 48% by mass, and particularly preferably 35% by mass to 48% by mass.

[0061] The resin film may have one or more white inorganic particle-containing layers, and the number of white inorganic particle-containing layers is preferably 1 to 5, more preferably 1 to 3.

[0062] The average thickness of the white inorganic particle-containing layer is preferably 5 μm or more and 200 μm or less, more preferably 10 μm or more and 119 μm or less, and even more preferably 20 μm or more and 117 μm or less. When the resin film has two or more white inorganic particle-containing layers, it is preferable that the average total thickness of the white inorganic particle-containing layers is within the above range. The average thickness of each layer included in the resin film can be obtained by averaging the thicknesses of any 10 points in a cross-sectional SEM image of the resin film.

[0063] In one embodiment, from the viewpoint of easily obtaining an appearance resembling Japanese paper, at least one surface layer of the resin film is a white inorganic particle-containing layer or a white inorganic particle-containing layer on which a printed layer described below is formed.

[0064] (thermoplastic resin layer) In one embodiment, the resin film further includes a thermoplastic resin layer (hereinafter simply referred to as a "thermoplastic resin layer") on at least one surface of the white inorganic particle-containing layer, the thermoplastic resin layer containing no white inorganic particles or containing a lower amount of white inorganic particles than the white inorganic particle-containing layer. As described above, the white inorganic particle-containing layer contains more than 50% by mass of white inorganic particles, which can cause the film to have a non-uniform thickness when stretched, potentially resulting in breakage of the film during stretching. In one embodiment of the present invention, by providing a thermoplastic resin layer containing no white inorganic particles (or containing a low amount of white inorganic particles) on at least one surface of the white inorganic particle-containing layer, it is possible to ensure the stretchability of the film while causing thickness unevenness in the white inorganic particle-containing layer, and to prevent the resin film from breaking.

[0065] A resin film having a thermoplastic resin layer can be suitably used, for example, as a heat-shrinkable film or a stretch film, and further as a heat-sealable packaging material such as a pillow packaging material.

[0066] A heat-shrinkable film is a film that can shrink when heated. The heat-shrinkable film can be placed over one or more objects and heated to shrink it to fit the shape of the object, allowing it to be used to wrap or package the object. Furthermore, the thermoplastic resin layer can function as a heat-sealing layer, making heat sealing possible.

[0067] Stretch film is self-elastic, meaning that it stretches when an expansion force is applied and returns to its original shape after the expansion force is released. Stretch film is stretched within its elastic deformation limits in both the longitudinal and transverse directions and wrapped around an object. The stretch film's recovery stress allows it to adhere tightly to one or more objects, allowing it to be used to wrap or package the objects.

[0068] Examples of thermoplastic resins include polyolefins such as polyethylene and polypropylene, chlorinated polyolefins, polystyrene, polyester, polyurethane, polyvinyl chloride, and (meth)acrylic resins, with polyolefins being preferred and polyethylene being more preferred.

[0069] Examples of polyethylene include ethylene homopolymers and copolymers of ethylene with other monomers. Examples of other monomers include α-olefins having 3 to 20 carbon atoms, vinyl acetate, (meth)acrylic acid, and (meth)acrylic acid esters. Examples of α-olefins having 3 to 20 carbon atoms include propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene, 3-methyl-1-butene, 4-methyl-1-pentene, and 6-methyl-1-heptene. Examples of (meth)acrylic acid esters include alkyl (meth)acrylates such as methyl (meth)acrylate and ethyl (meth)acrylate.

[0070] Examples of the copolymer include a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms, a copolymer of ethylene and at least one selected from vinyl acetate, (meth)acrylic acid, and (meth)acrylic acid esters, and a copolymer of ethylene, an α-olefin having 3 to 20 carbon atoms, and at least one selected from vinyl acetate, (meth)acrylic acid, and (meth)acrylic acid esters.

[0071] Examples of polyethylene include high-density polyethylene (HDPE), medium-density polyethylene (MDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), very low-density polyethylene (VLDPE), ethylene-vinyl acetate copolymer, ethylene-(meth)acrylic acid ester copolymer, and ethylene-(meth)acrylic acid copolymer.

[0072] Among polyethylenes, LLDPE is preferred. That is, the thermoplastic resin layer is preferably a layer containing linear low-density polyethylene (LLDPE). Since LLDPE has excellent stretchability, stretching treatment during resin film production can be carried out smoothly. Furthermore, a resin film having an LLDPE-containing layer is suitable as a heat-shrinkable film or a stretch film.

[0073] Among LLDPEs, LLDPEs having a structural unit derived from an α-olefin having 6 to 8 carbon atoms as a comonomer unit are preferred. By using LLDPE with long side chains in the thermoplastic resin layer, moderate partial breakage occurs in the white inorganic particle-containing layer during stretching, increasing the surface reflection roughness, while such breakage is suppressed in the thermoplastic resin layer, allowing it to be stretched well and maintaining the film shape.

[0074] The melt flow rate (MFR) of the polyolefin is preferably 0.1 g / 10 min to 100 g / 10 min, more preferably 0.5 g / 10 min to 30 g / 10 min, and even more preferably 1 g / 10 min to 10 g / 10 min. The MFR is measured by Method A according to JIS K7210-1995, for example, at a temperature of 190°C for polyethylene and at a temperature of 230°C for polypropylene under a load of 2.16 kg.

[0075] The polyolefin may be a polyolefin derived from a fossil fuel or a polyolefin derived from biomass. Specific and preferred examples of the biomass-derived polyolefin are as described above.

[0076] The thermoplastic resin layer can contain one or more types of thermoplastic resins. The content of the thermoplastic resin in the thermoplastic resin layer is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 72% by mass or more, and particularly preferably 75% by mass or more. In one embodiment, the content of the thermoplastic resin in the thermoplastic resin layer is 99% by mass or less, preferably 95% by mass or less, and more preferably 90% by mass or less.

[0077] The content of the white inorganic particles in the thermoplastic resin layer is preferably 50% by mass or less, more preferably 30% by mass or less, even more preferably 28% by mass or less, and particularly preferably 25% by mass or less. This allows the thermoplastic resin layer to maintain good extensibility that can withstand stretching. In one embodiment, the content of the white inorganic particles in the thermoplastic resin layer is 1% by mass or more, preferably 5% by mass or more, and more preferably 10% by mass or more.

[0078] The thermoplastic resin layer may further contain additives other than the white inorganic particles, such as a heat stabilizer, an ultraviolet absorber, an antioxidant, a coupling agent, a lubricant, a dispersant, and an antistatic agent. The thermoplastic resin layer may contain one or more additives.

[0079] The resin film may have one or more thermoplastic resin layers, and the number of thermoplastic resin layers is preferably 1 to 5, more preferably 1 to 3.

[0080] The average thickness of the thermoplastic resin layer is preferably 1 μm or more and 50 μm or less, more preferably 3 μm or more and 30 μm or less, and even more preferably 5 μm or more and 25 μm or less. When the resin film has two or more thermoplastic resin layers, it is preferable that the average total thickness of the thermoplastic resin layers is within the above range.

[0081] In one embodiment, the resin film includes a first white inorganic particle-containing layer, a second white inorganic particle-containing layer as an intermediate layer, and a thermoplastic resin layer, in this order in the thickness direction. The resin film may include a printed layer, as described below, on the first white inorganic particle-containing layer. In one embodiment, the first white inorganic particle-containing layer constitutes the outer layer of the packaging material, and the thermoplastic resin layer constitutes the inner layer of the packaging material and functions as a heat-seal layer.

[0082] (Printing layer) The resin film may further include a printed layer on the white inorganic particle-containing layer. The white inorganic particle-containing layer has excellent printability, so that the printed layer can be easily formed on the white inorganic particle-containing layer.

[0083] The printed layer is a layer formed by printing for decoration or to display the product name, contents, raw material names, expiration date, manufacturer and seller, etc. The printed layer includes a pattern layer having any desired pattern such as a picture, photograph, letter, number, figure, symbol, and pattern. The printed layer may further include a background color layer formed by printing to make the pattern of the pattern layer stand out.

[0084] In one embodiment, the printed layer contains a colorant and a binder resin. In one embodiment, the ink composition for forming the printed layer contains a colorant, a binder resin, and a solvent. The printed layer can be formed by printing the ink composition on the white inorganic particle-containing layer by a known printing method such as gravure printing, flexographic printing, or screen printing.

[0085] As the colorant, for example, conventionally known pigments and dyes can be used. As the binder resin, for example, conventionally known binder resins such as chlorinated polyolefin, vinyl chloride-vinyl acetate copolymer resin, (meth)acrylic resin, polyamide, and polyurethane can be used.

[0086] The print layer may be provided on the entire surface of the white inorganic particle-containing layer, or may be provided on a part of the surface. The average film thickness of the printed layer is preferably 0.1 μm or more and 10 μm or less, more preferably 1 μm or more and 5 μm or less, and even more preferably 1 μm or more and 3 μm or less.

[0087] (Anchor coat layer) The resin film may further include an anchor coat layer between the white inorganic particle-containing layer and the print layer. The anchor coat layer is a layer for improving adhesion between the white inorganic particle-containing layer and the print layer.

[0088] An example of a material for forming the anchor coat layer is polyethyleneimine. The anchor coat layer can be formed by applying a coating composition containing the above material and a solvent onto the white inorganic particle-containing layer.

[0089] (protective layer) The resin film may further include a protective layer on the printed layer to protect the printed layer, as long as the Japanese paper-like appearance is maintained. The protective layer can be provided to protect the printed layer from external impact, friction, etc.

[0090] The protective layer is preferably colorless and transparent in order to maintain the appearance of Japanese paper or to maintain the visibility of the printed layer. Examples of materials for forming the protective layer include ultraviolet-curable ink and electron beam-curable ink. The protective layer is preferably provided in the same area as the printed layer or in an area wider than the printed layer so as to encompass the printed layer. The average thickness of the protective layer is preferably 0.1 μm or more and 10 μm or less.

[0091] <Method of manufacturing resin film> The resin film can be produced by, for example, inflation extrusion or T-die extrusion. In one embodiment, a resin composition containing white inorganic particles and a resin material for forming the white inorganic particle-containing layer and a thermoplastic resin composition containing no white inorganic particles or containing a small amount of white inorganic particles for forming the thermoplastic resin layer are co-extruded using an inflation extrusion machine or a T-die extrusion machine, and the resulting laminate is stretched to produce a resin film. In one embodiment, the temperature of the molding machine is set to a temperature at least 10°C higher than the melting point of the resin used. However, if it is desired to increase the production speed, a higher temperature is set, but ultimately the temperature may be set to balance various factors including production stability. In one embodiment, the temperature of the molding machine is set to a range of 120°C or higher and 280°C or lower.

[0092] In one embodiment, a resin composition containing white inorganic particles and a resin material is produced using a masterbatch containing a high concentration of white inorganic particles, which can be produced using an extruder that combines a twin screw, multiple feed ports, a loss-in-weight feeder, a die that extrudes molten resin as strands, and a pelletizer.

[0093] The stretching treatment can improve the appearance of the resin film. Specifically, the stretching treatment can cause unevenness in film thickness, uneven surface reflection, and uneven voids, which results in an uneven surface of the layer formed from the resin composition containing white inorganic particles and a resin material, resulting in a resin film with a Japanese paper-like appearance. In one embodiment, the layer formed from the resin composition containing white inorganic particles and a resin material is moderately partially broken by the stretching treatment, becoming thinner and causing significant unevenness in film thickness, while the layer formed from the thermoplastic resin composition has excellent extensibility and therefore maintains its film shape.

[0094] The inflation molding machine can also stretch the laminate, which allows for the production of a stretched film, which is an embodiment of a resin film, and therefore further improves production efficiency.

[0095] The stretched film may be a uniaxially stretched film or a biaxially stretched film. From the viewpoint that a non-uniform appearance can be easily obtained, the uniaxially stretched film is preferred, and a uniaxially stretched film stretched in the machine direction (MD) of the film is more preferred.

[0096] The stretching ratio in the machine direction (MD) and / or transverse direction (TD) of the stretched film is preferably 1.1 to 10 times, more preferably 1.2 to 5 times, and even more preferably 1.2 to 2.5 times.

[0097] When the stretching ratio is 1.1 times or more, for example, a resin film with a better appearance can be obtained and the printability of the resin film can be improved.When the stretching ratio is 10 times or less, the laminate can be stretched well.

[0098] <Applications of resin film> Since the resin film of the present invention has an appearance similar to that of Japanese paper, it can be suitably used as a packaging material, preferably as a packaging material for products, and more preferably as a packaging material for gifts, i.e., a packaging material for wrapping gifts (products).

[0099] The resin film of the present invention is useful as a heat-sealable packaging material. For example, the resin film of the present invention can be heat-sealed using a heat-sealing method such as a side seal type, a two-sided seal type, a three-sided seal type, a four-sided seal type, an envelope seal type, a flared seal type (pillow seal type), a pleated seal type, a flat bottom seal type, a square bottom seal type, or a gusset seal type to produce packaging bags of various embodiments. Furthermore, for example, the packaging material can also be a self-standing packaging bag (standing pouch).

[0100] For example, in the case of a resin film having a white inorganic particle-containing layer and a thermoplastic resin layer, the resin film can be folded in half and overlapped so that the white inorganic particle-containing layer is located on the outside and the thermoplastic resin layer is located on the inside, and then heat-sealed at the edges, etc., to produce a packaging material, or by overlapping multiple resin films so that the thermoplastic resin layers face each other and heat-sealing at the edges, etc. Heat-sealing can be performed by known methods such as bar sealing, rotary roll sealing, belt sealing, impulse sealing, high-frequency sealing, and ultrasonic sealing.

[0101] In one embodiment, the resin film of the present invention has an appearance similar to that of Japanese paper and is excellent in tearability and therefore in openability, and is therefore useful as a pillow packaging material.

[0102] The resin film of the present invention can be suitably used as a printing substrate, which is an alternative material to conventional printing paper substrates (e.g., synthetic paper, recycled paper) used in the printing industry. Examples of printing substrates include business cards, booklets, pamphlets, leaflets, posters, stickers, seals, labels, tickets, tags, shipping tags, cards, and folding boxes.

[0103] The resin film of the present invention is also useful as a material for forming containers for storing food and beverages, flower pots, and other containers; food wrap; bags (e.g., carrier bags, garbage bags), drinking straws, and the like; and disposable cutlery. Containers can be produced, for example, by vacuum molding using the resin film.

[0104] As described above, the resin film of the present invention is useful as a heat-shrinkable film or a stretch film, specifically as a tight-pack packaging material, for example, to wrap or package products, and is also useful as a label for food containers or beverage bottles.

[0105] [Packaging] The packaging of the present invention comprises: A packaging material made of the resin film of the present invention; An item to be packaged that is at least partially packaged with the packaging material; Equipped with.

[0106] Examples of packaged items include boxes with cubic and rectangular shapes, cylindrical and polygonal cylindrical shapes, food products such as fresh food and prepared dishes, plants, agricultural products, books, and clothing. The boxes and cylindrical bodies contain goods or products such as food products, beverages, agricultural products, cosmetics, medicines, books, clothing, toys, and electronic devices.

[0107] In the package of the present invention, the entire surface of the packaged item may be wrapped with the resin film, or only a portion of the packaged item may be wrapped with the resin film.

[0108] Examples of the former include caramel wrapping, diagonal wrapping, and square wrapping. As described above, the packaging may be in various forms (packaging bags) heat-sealed by the heat-sealing method, and a specific example is pillow wrapping.

[0109] An example of the latter is strap packaging, which uses a resin film narrower than the width of the packaged item to partially wrap the packaged item so that both sides of the packaged item are exposed.

[0110] The present invention relates to, for example, the following [1] to

[15] . [1] A resin film having a surface reflection roughness of 2.0 or more, defined as the average value of the residual standard deviation σ of the surface reflection light intensity relative to the regression line. [2] A resin film having an average thickness of 25.0 μm or more and a thickness ratio defined as the ratio of the maximum thickness to the minimum thickness of 2.0 or more. [3] The resin film according to [1] or [2] above, which comprises a layer containing white inorganic particles and a resin material, the content of the white inorganic particles being more than 50% by mass. [4] The resin film according to [3] above, wherein the white inorganic particles are calcium carbonate. [5] The resin film according to the above [3] or [4], wherein in a cross-sectional image of the resin film, voids are present around at least some of the white inorganic particles. [6] The resin film according to any one of the above [3] to [5], wherein the resin material contains polyolefin. [7] The resin film according to [6] above, wherein the polyolefin comprises a biomass-derived polyolefin. [8] The resin film according to the above [6] or [7], wherein the polyolefin comprises at least one selected from polyethylene and polypropylene. [9] The resin film according to any one of the above [3] to [8], further comprising a thermoplastic resin layer having a white inorganic particle content of 50% by mass or less on at least one side of the layer containing white inorganic particles and a resin material, the white inorganic particle content exceeding 50% by mass.

[10] The resin film according to [9] above, wherein the thermoplastic resin layer contains linear low-density polyethylene.

[11] The resin film according to

[10] above, wherein the thermoplastic resin layer contains a linear low-density polyethylene having, as a comonomer unit, a structural unit derived from an α-olefin having 6 to 8 carbon atoms.

[12] The resin film according to any one of the above [1] to

[11] , which is uniaxially or biaxially stretched.

[13] The resin film according to any one of the above [1] to

[12] , which is a packaging material.

[14] The resin film according to

[13] above, wherein the packaging material is a pillow packaging material.

[15] A package comprising a packaging material made of the resin film according to any one of [1] to

[12] above, and an item to be packaged, at least a portion of which is packaged in the packaging material. [Example]

[0111] The resin film of the present invention will be described in more detail with reference to examples, but the resin film of the present invention is not limited to these examples.

[0112] [Example 1] A masterbatch was obtained by kneading 65 parts by mass of "Mamacalso (registered trademark)" (heavy calcium carbonate, manufactured by Nitto Funka Kogyo Co., Ltd.) and 35 parts by mass of "SLH118" (biomass polyethylene, manufactured by Braskem) in a twin-screw extruder.

[0113] 97 parts by mass of the masterbatch and 3 parts by mass of "L-MODU (registered trademark) S901" (manufactured by Idemitsu Kosan Co., Ltd., homopolypropylene) were dry-blended to obtain a resin composition (1).

[0114] 72 parts by mass of "Evolue (registered trademark) SP0510" (manufactured by Prime Polymer Co., Ltd., LLDPE) and 28 parts by mass of the masterbatch were dry blended to obtain a resin composition (2).

[0115] Next, resin composition (1) for the outer layer, resin composition (1) for the intermediate layer, and resin composition (2) for the inner layer were each fed into an inflation extrusion molding machine, and the three layers were co-extruded at an extrusion ratio (thickness ratio) of outer layer:intermediate layer:inner layer = 2:6:2 to form a laminate, which was then stretched in-line in the machine direction (MD) and then wound up. The stretching ratio was 1.7 times.

[0116] As a result, a stretched laminate with an average thickness of 52.4 μm was obtained, which had an outer layer (front side) containing calcium carbonate and biomass polyethylene, an intermediate layer containing calcium carbonate and biomass polyethylene, and an inner layer (back side) containing a layer with a high LLDPE ratio. The calcium carbonate content in the stretched laminate was 50% by mass or more. " / " indicates the boundary between layers.

[0117] [Examples 2 to 5] A stretched laminate was obtained in the same manner as in Example 1, except that the extrusion amount was changed to change the thickness of the laminate before stretching so that the thickness of the laminate after stretching would be approximately 40 to 70 μm, and the stretching ratio was changed as shown in Table 1.

[0118] [Example 6] Resin composition (3) was obtained by dry blending 98 parts by mass of a calcium carbonate masterbatch (product name UH-25, manufactured by Earth Create Co., Ltd., calcium carbonate 70% by mass / homopolypropylene 30% by mass) and 2 parts by mass of "L-MODU (registered trademark) S901" (manufactured by Idemitsu Kosan Co., Ltd., homopolypropylene).

[0119] A resin composition (4) was obtained by dry-blending 8 parts by mass of LLDPE (a product synthesized using a metallocene catalyst), 90 parts by mass of a calcium carbonate masterbatch (product name UH-25, manufactured by Earth Create Co., Ltd., calcium carbonate 70% by mass / homopolypropylene 30% by mass), and 2 parts by mass of "L-MODU (registered trademark) S901" (manufactured by Idemitsu Kosan Co., Ltd., homopolypropylene).

[0120] A resin composition (5) was obtained by dry blending 68 parts by mass of LLDPE (a product synthesized using a metallocene catalyst) and 32 parts by mass of calcium carbonate masterbatch (containing 80% by mass of calcium carbonate).

[0121] Next, resin composition (3) for the outer layer, resin composition (4) for the intermediate layer, and resin composition (5) for the inner layer were each fed into an inflation extrusion molding machine, and the three layers were co-extruded at an extrusion ratio (thickness ratio) of outer layer:intermediate layer:inner layer = 18:92:50 to form a laminate, which was then stretched in-line in the machine direction (MD) and then wound up. The stretching ratio was 2.3 times. As a result, a stretched laminate having an average thickness of 48.8 μm was obtained.

[0122] [Example 7] A stretched laminate with an average thickness of 32.5 μm was obtained in the same manner as in Example 6, except that the extrusion amount was changed to change the film thickness of the laminate before stretching, the extrusion ratio (thickness ratio) was outer layer:intermediate layer:inner layer = 8:44:24, and the stretching ratio was 1.5 times.

[0123] The products used in the examples are listed below. Mamacalso (registered trademark): Ground calcium carbonate, average particle size 2.2 μm, Manufactured by Nitto Funka Kogyo Co., Ltd. SLH118: Biomass polyethylene, LLDPE having 1-butene and 1-hexene units as comonomer units, MFR = 1.0 g / 10 min, manufactured by Braskem UH-25: Calcium carbonate masterbatch, calcium carbonate 70% by mass / homopolypropylene 30% by mass, manufactured by Earth Create Co., Ltd. L-MODU (registered trademark) S901: MFR = 50 g / 10 min, low stereoregularity homopolypropylene synthesized using a metallocene catalyst, manufactured by Idemitsu Kosan Co., Ltd. Evolue® SP0510: MFR = 1.2 g / 10 min, LLDPE synthesized using a metallocene catalyst and containing 1-hexene units as comonomer units, manufactured by Prime Polymer Co., Ltd.

[0124] [Comparative Example 1] Shoji paper (manufactured by Daiso Industries Co., Ltd.) was used as the shoji paper. Comparative Example 2 Biznet copy paper A4 (manufactured by Noesu Co., Ltd.) was used as the copy paper. Comparative Example 3 A resin film was prepared as stone paper using the following procedure. Earth Create Co., Ltd.'s UH-25 (a PP masterbatch containing 70% by mass of calcium carbonate) and Prime Polymer Co., Ltd.'s Hi-Zex 5000SR (HDPE) were blended at a mass ratio of 9:1 to obtain resin composition (6). Prime Polymer Co., Ltd.'s E-100GPL (PP), Prime Polymer Co., Ltd.'s Hi-Zex 5000SR (HDPE), a PP masterbatch containing 40% by mass of flaky boehmite, and a PP masterbatch containing 50% by mass of titanium oxide filler were dry-blended at a mass ratio of 1:4:2:3 to obtain resin composition (7). Resin composition (6) was used for the middle layer, and resin composition (7) was used for the outer and inner layers in a two-type, three-layer T-die extruder. The layer ratio (thickness ratio) of outer layer:middle layer:inner layer was 1:8:1 to obtain stone paper. The average thickness was 102.7 μm. Comparative Example 4 The laminate before stretching in Example 1 was used. However, the extrusion amount was changed to form a laminate so that the average film thickness was approximately the same as that of the laminate after stretching in Example 1. [Example 8] 90 parts by mass of "Evolue (registered trademark) SP0510" (Prime Polymer Co., Ltd., LLDPE) and 10 parts by mass of the same masterbatch as in Example 1 were dry-blended to obtain a resin composition (8). Subsequently, resin composition (1) for the outer layer, resin composition (1) for the intermediate layer, and resin composition (8) for the inner layer were each charged into an inflation extrusion molding machine, and three layers were co-extruded so that the extrusion ratio (thickness ratio) was outer layer:intermediate layer:inner layer = 33:34:33 to form a laminate. The laminate was stretched in-line in the machine direction (MD) and then wound up. The stretching ratio was 1.5 times. Here, by keeping the extrusion rate low, a resin film with an average thickness of 23.2 μm was obtained.

[0125] [Surface reflection roughness] The stretched laminates obtained in Examples 1 to 8, the papers of Comparative Examples 1 and 2, the stone paper of Comparative Example 3, and the laminate of Comparative Example 4 are hereinafter referred to as "samples." The surface reflective roughness of the samples was determined based on the method described above in the section (Method for measuring surface reflective roughness). As an example, Figure 1 shows a graph plotting the stretched laminate obtained in Example 1, with the horizontal axis representing pixels and the vertical axis representing brightness values ​​in 256 gradations.

[0126] Surface reflection roughness was measured for the X direction (TD direction) and the Y direction (MD direction) perpendicular to the X direction of the sample. Samples with a σ of 2.0 or more and samples with a film thickness ratio of 2.0 or more had an appearance similar to Japanese paper when visually observed. Figure 2 shows a photograph of the appearance of the sample of Example 1, and Figure 3 shows a photograph of the appearance of the sample of Comparative Example 3. The vertical direction in the figure corresponds to the MD direction.

[0127] [water resistance] The sample was cut into a size of 100 mm x 100 mm, its weight was measured, and then it was immersed in tap water at 25°C for 1 hour. After this, the sample was taken out of the water, water droplets on the surface were removed, and the weight was measured again. The water resistance was evaluated based on the weight increase rate according to the following criteria. · Yes: Weight increase was less than 10%. None: Weight increase was 10% or more.

[0128] [Cross-section analysis and void evaluation] The obtained sample was embedded in an ultraviolet (UV) curable resin and then irradiated with UV to produce an embedded sample. The embedded sample was cut using a microtome. The obtained cross section was observed using a scanning electron microscope "S-4800" (trade name, manufactured by Hitachi High-Technologies Corporation). As an example, an SEM image of a cross section parallel to the TD direction of the white portion of the surface SEM image of the stretched laminate obtained in Example 1 is shown in FIG. 4 (voids are, for example, the areas surrounded by ellipses), an SEM image of a cross section parallel to the MD direction of the white portion is shown in FIG. 5, an SEM image of a cross section parallel to the TD direction of the nearly transparent portion of the surface SEM image is shown in FIG. 6, and an SEM image of a cross section parallel to the MD direction of the nearly transparent portion is shown in FIG. 7.

[0129] [Maximum strength] A parallel clamping jaw JM-JFM-500N was set on an A&D Corporation "MCT-2150" with a chuck spacing of 40 mm. The above sample, 60 mm long and 15 mm wide, cut with the long side in the MD direction, was set and pulled at a speed of 300 mm / min. After yield or break, where the stress of the sample does not increase but elongation continues, the point at which the stress no longer increases on the graph of displacement and stress (SS curve) was taken as the yield point, and the stress at this point was taken as the maximum strength (N / 15 mm).

[0130] [Repeated 10% elongation strain] A parallel clamping jaw JM-JFM-500N was set on an A&D Corporation "MCT-2150" with a chuck spacing of 40 mm. The above sample, cut out with a test piece length of 60 mm and width of 15 mm with the long side in the MD direction, was set and pulled 4 mm at a speed of 100 mm / min, then returned to its original position, and pulled again 4 mm. After pulling twice, it was returned to its original position and checked to see if any sagging or deformation remained that could be seen visually.

[0131] None: No visible deformation or sagging occurs. - Yes: Visible deformation or sagging remains after the test. The shape before the test does not return to normal. Break: The sample broke after the test.

[0132] [Wrapping processability] Using the above samples, a packaging test was conducted using an automatic banding packaging machine "Tight Packer NTP-45" manufactured by Nippon Packaging Machinery Co., Ltd. The boxes to be packaged were not entirely wrapped, but rather banded as follows: First, one sample was wrapped around the box once, in the same way as wrapping the band around the box, to create a banded state. Next, both ends of one sample were heat-sealed while tension was applied to the banded sample, and then the tension was released, completing the banded packaging with the sample wrapped around the box once.

[0133] The wrapping processability was evaluated according to the following criteria. ◯: A good product was obtained in which the sample was wrapped without any damage in a banded state by the packaging machine. △: There was no significant damage to the sample when it was wrapped in a wrapping machine. A small crack was observed in the heat-welded area. ×: Tested with a packaging machine, The sample broke after packaging and no good products were obtained. XX: The sample is not heat-welded, so the test cannot be performed in principle.

[0134] [Hayes] The haze values ​​of the samples obtained in the examples and comparative examples were measured in accordance with JIS K7136 using a haze meter (HM-150N manufactured by Murakami Color Research Laboratory Co., Ltd.).

[0135] [Film thickness measurement] The film thickness of the samples obtained in the examples and comparative examples was measured on a surface plate using a Nikon Digimicro MF-501 and a counter MFC-101A, with an off-center probe PB-D attached to the sample contact area. Each measurement position was shifted approximately 3 mm in the TD direction, with 10 measurement points in each row. Measurements were repeated for five rows, with each row shifted approximately 5 mm in the MD direction, for a total of 50 actual measurements. The average film thickness of the 50 points was calculated as the average film thickness, and the ratio of the maximum film thickness to the minimum film thickness was calculated as the film thickness ratio.

[0136] [Table 1]

[0137] [Pillow packaging test] Using the stretched laminate obtained in Example 6, a test was conducted using a compact, high-speed, horizontal pillow automatic packaging machine, and pillow packaging bags were obtained that were free of tearing or deformation when filled with a 50 mm x 5 mm diameter rod-shaped resin molding.

[0138] The pillow packaging obtained here could be opened with light force even when there were no tears in either the MD or TD, and was effective as packaging that allowed for easy removal of the contents. For example, when opening in the MD, the bag could be torn with light force at the beginning, and then with even lighter force thereafter.

Claims

1. White inorganic particles (excluding white inorganic particles that have been surface-treated with a fatty acid-based dispersant). ) and a resin material, A resin film having a surface reflection roughness of 2.0 or more, which is defined as the average value of the residual standard deviation σ of the surface reflection light intensity relative to a regression line.

2. The resin film according to claim 1 , comprising a layer having a content ratio of the white inorganic particles exceeding 50% by mass.

3. The resin film according to claim 2 , wherein the white inorganic particles are calcium carbonate.

4. The resin film according to claim 2 or 3, wherein voids are present around at least some of the white inorganic particles in a cross-sectional image of the resin film.

5. The resin film according to any one of claims 2 to 4, wherein the resin material comprises a polyolefin.

6. The resin film according to claim 5 , wherein the polyolefin comprises a biomass-derived polyolefin.

7. The resin film according to claim 5 or 6, wherein the polyolefin comprises at least one selected from polyethylene and polypropylene.

8. on at least one surface of the layer containing white inorganic particles and a resin material, the content of the white inorganic particles being more than 50% by mass, The resin film according to any one of claims 2 to 7, further comprising a thermoplastic resin layer having a content of white inorganic particles of 50 mass% or less.

9. The resin film according to claim 8 , wherein the thermoplastic resin layer contains linear low-density polyethylene.

10. 10. The resin film according to claim 9, wherein the thermoplastic resin layer contains a linear low-density polyethylene having, as a comonomer unit, a structural unit derived from an α-olefin having 6 to 8 carbon atoms.

11. The resin film according to any one of claims 1 to 10, which is uniaxially or biaxially stretched.

12. The resin film according to any one of claims 1 to 11, which is a packaging material.

13. The resin film according to claim 12, wherein the packaging material is a pillow packaging material.

14. A packaging material made of the resin film according to any one of claims 1 to 11; A package comprising an item to be packaged, at least a portion of which is packaged in the packaging material.

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