WO2025041554A1 - Polyethylene-based resin film, laminate, and package - Google Patents

Abstract

Provided is a polyethylene-based resin film excellent in scratch resistance, heat sealability, blocking resistance and slipperiness, and in which wrinkles are not prone to occur even when a roll of the film is conveyed by rolling.　The present invention is a polyethylene-based resin film having a heat seal layer made of a polyethylene-based resin composition on a surface layer, and a laminate layer made of a polyethylene-based resin composition on the other surface layer, wherein at least one surface layer satisfies 1) and 2). 1) The surface layer has protrusions, and the protrusion density in a slice level at a height of 250 nm when slice levels is set at intervals of 250 nm from a reference surface is 160/mm² or more. 2) The amount of change in haze after 100 abrasions with a load of 200 g between surface layers is 3.0% or less.

Description

Polyethylene resin film, laminate, and packaging material

The present invention relates to a polyethylene resin film, a laminate containing the polyethylene resin film, and a package comprising the laminate.

Packaging is used to package and transport a variety of foods, including fresh produce, prepared foods, and confectionery. The use of packaging not only allows food to be delivered to consumers efficiently, but also delays food spoilage, extends the expiration date, and prevents dust and other debris from getting into the food during transport and storage. Packaging is manufactured by laminating multiple films. Sealant films are generally used by laminating them with a base film. If the sealant film is stored in roll form after lamination with the base film, blocking can occur between the sealant film and the base film, making it difficult to unwind the laminate film before bag making, or blocking can occur between the sealant films that form the inner surface of the bag during bag making, making it difficult to fill the food.

Therefore, a polyethylene resin film has been reported that uses inorganic fine powder or inorganic fine particles such as silica in a polyethylene resin (Patent Document 1). However, this technology has the problem that the scratch resistance of the film is insufficient, and when the film roll is processed by an automatic packaging machine, the film is scratched, reducing the visibility of the contents.

Also known is a polyethylene resin film that contains particles made of polyethylene resin as an antiblocking agent added to the polyethylene resin film (Patent Document 2, Patent Document 3).

Patent No. 6467825 International Publication No. 2020/217931 International Publication No. 2020/217932

When film rolls are transported from the manufacturing plant to the plant where they are to be used, they are packaged so that they are not damaged during transportation. This packaging work is sometimes done manually, but in an increasing number of cases, it is done partially or entirely automatically using automatic packaging machines, etc., in order to reduce costs. The inventors' research has revealed that wrinkles occur when film rolls are rolled and transported using automatic packaging machines, etc. Furthermore, the inventors' research has revealed that when a film roll wound up in the slitting process is moved horizontally to the packaging process, it is accompanied by movement back and forth and side to side, so the roll may be rolled, but when the roll is pushed or stopped, an external force is applied partially to the body of the roll, which causes the film to have poor slipperiness in the areas where force is applied, resulting in wrinkles.

The present invention aims to provide a polyethylene resin film that is excellent in scratch resistance, heat sealability, blocking resistance and slipperiness, and that is less likely to wrinkle even when transported by rolling a film roll.

The inventors conducted extensive research to achieve this objective and discovered that by controlling the particle size and content of the spherical particles made of polyethylene resin and the spherical inorganic particles, at least one of the surfaces can be given a special surface structure with the following characteristics, which improves slipperiness and suppresses wrinkles when the film roll is rolled and transported, while also improving scratch resistance, suppressing scratches caused by rubbing between the inner surfaces of the bag when used as a package, and suppressing fine scratches on the food contents, making it less likely for the food to lose its flavor.

[1] A polyethylene-based resin film having a heat seal layer made of a polyethylene-based resin composition on one surface layer and a laminate layer made of a polyethylene-based resin composition on the other surface layer, wherein at least one of the surface layers satisfies the following 1) and 2).
1) The surface layer has protrusions, and when slice levels are set at 250 nm intervals from a reference surface, the protrusion density at a slice level having a height of 250 nm is 160 pcs/ ^mm2 or more.
2) The change in haze after the surface layers are abraded together 100 times under a load of 200 g is 3.0% or less.
[2] The polyethylene-based resin film according to [1], wherein the weighted average density of the polyethylene-based resin composition constituting the heat seal layer is lower than the weighted average density of the polyethylene-based resin composition constituting the laminate layer.
[3] The polyethylene-based resin film according to [1] or [2], wherein the heat seal layer contains spherical particles made of a polyethylene-based resin, and the spherical particles made of a polyethylene-based resin have a viscosity average molecular weight of 1.5 million or more and 2.5 million or less.
[4] The polyethylene-based resin film according to any one of [1] to ^[3] , wherein the weighted average density of the polyethylene-based resin composition constituting the laminate layer is 910 kg/ ^m3 or more and 945 kg/m3 or less, and the weighted average density of the polyethylene-based resin composition constituting the heat seal layer is 900 kg/m3 ^or more and 930 kg/m3 or ^less .
[5] The polyethylene-based resin film according to any one of [1] to [ ^4] , wherein one or more core layers are present between the heat seal layer and the laminate layer, and the weighted average density of the polyethylene-based resin composition constituting the core layer is 910 kg/m3 or more and 930 kg/ ^m3 or less.
[6] The polyethylene-based resin film according to any one of [1] to [5], wherein the polyethylene-based resin contained in the polyethylene-based resin composition constituting the laminate layer, and the polyethylene-based resin contained in the polyethylene-based resin composition constituting the heat seal layer are linear low-density polyethylene.
[7] The polyethylene-based resin film according to any one of [1] to [6], wherein the arithmetic mean roughness SRa of at least one of the surfaces of the laminate layer and the heat seal layer is 60 nm or more and 200 nm or less, and the maximum height SRmax is 2 μm or more and 9 μm or less.
[8] The polyethylene resin film according to any one of [1] to [7], wherein the change in haze after the heat seal layers are abraded 100 times under a load of 200 g is 3.0% or less.
[9] A laminate comprising at least one film selected from the group consisting of a uniaxially oriented polyolefin-based resin film, a biaxially oriented polyolefin-based resin film, a uniaxially oriented polyamide-based resin film, a biaxially oriented polyamide-based resin film, a uniaxially oriented polyester-based resin film, and a biaxially oriented polyester-based resin film, and the polyethylene-based resin film according to any one of [1] to [8].
[10] A packaging material comprising the laminate described in [9].

The present invention is a polyethylene resin film that has excellent scratch resistance, heat sealability, blocking resistance, and slipperiness, and is suitable for use as a non-oriented polyethylene resin film that is less likely to wrinkle even when transported by rolling a film roll.

(Polyethylene resin film)
The present invention will be described in detail below.
The polyolefin resin film has a laminate layer on one surface layer and a heat seal layer on the other surface layer. The heat seal layer and the laminate layer are layers located on the surface side of the film, and the polyolefin resin film may have one or more core layers between them. The laminate layer is a layer suitable for bonding a base film such as a uniaxially oriented or biaxially oriented polyamide film, and is preferably laminated with the base film via an adhesive resin. The laminate layer can also be printed. The heat seal layer is a layer suitable for producing a package by overlapping two sheets of the laminate and heat sealing them so that the polyolefin resin film of the obtained laminate is on the inside.

(Thickness of polyethylene resin multi-layer film)
The lower limit of the thickness of the polyethylene resin film is preferably 15 μm, more preferably 20 μm, and even more preferably 25 μm. When it is 15 μm or more, heat seal strength is easily obtained. The upper limit of the thickness of the polyethylene resin film is preferably 100 μm, more preferably 80 μm, even more preferably 60 μm, and even more preferably 50 μm. When it is 100 μm or less, the film does not have too strong a stiffness and is easy to process, and a suitable package is easily produced, which is also preferable in terms of cost.

The weighted average density of the polyethylene resin composition that constitutes the heat seal of the polyethylene resin film is preferably smaller than the weighted average density of the polyethylene resin composition that constitutes the laminate layer. The organic lubricant contained therein does not easily migrate to layers with higher density, so it is effective in maintaining the slipperiness of the heat seal layer after lamination and in maintaining the laminate strength over time.

(Multi-layer structure)
The polyethylene resin film preferably has a multi-layer structure of two or more layers including a heat seal layer and a laminate layer. In the case of three or more layers, the polyethylene resin film may have one or more other layers such as a core layer in addition to the laminate layer and the heat seal layer.

(Heat seal layer)
The heat seal layer in the present invention is made of a polyethylene resin composition. The polyethylene resin composition mainly contains a polyethylene resin, and preferably also contains particles made of a polyethylene resin. The polyethylene resin composition preferably contains 50% by weight or more of a polyethylene resin, more preferably 70% by weight or more, and even more preferably 90% by weight or more. The upper limit of the content of the polyethylene resin contained in the polyethylene resin composition is not particularly limited, but for example, the polyethylene resin composition preferably contains 99.5% by weight or less of a polyethylene resin, and more preferably contains 99.0% by weight or less.
The lower limit of the thickness ratio of the heat seal layer of the polyethylene resin film is preferably 12%, more preferably 18%. By making it 12% or more, good heat seal strength can be exhibited.
The upper limit of the thickness ratio of the heat seal layer of the polyethylene resin film is preferably 50%, more preferably 40%, and further preferably 30%. By setting it to 50% or less, blocking resistance can be improved.

(Polyethylene Resin of Heat Seal Layer)
The polyethylene resin contained in the polyethylene resin composition constituting the heat seal layer in the present invention preferably contains a homopolymer of an ethylene monomer, a copolymer of an ethylene monomer and an α-olefin, or a mixture thereof, and more preferably contains a copolymer of an ethylene monomer and an α-olefin. The α-olefin preferably contains propylene, butene-1, hexene-1, 4-methylpentene-1, octene-1, decene-1, or the like, or a combination thereof, and more preferably contains hexene-1. The polyethylene resin is preferably a linear low density polyethylene. An example of the linear low density polyethylene is linear short-chain branched polyethylene. The density of the linear low density polyethylene is preferably 900 to 930 kg/m ³ .

The lower limit of the melt flow rate (hereinafter sometimes referred to as MFR) of the polyethylene resin contained in the polyethylene resin composition constituting the heat seal layer is preferably 1.5 g/10 min, more preferably 2.0 g/10 min, and even more preferably 2.3 g/10 min. If it is 1.5 g/10 min or more, it is easy to process into a film by extrusion molding, and the viscosity average molecular weight of the particles made of the polyethylene resin is unlikely to decrease.
The upper limit of the MFR of the polyethylene resin contained in the polyethylene resin composition constituting the heat seal layer is preferably 7.0 g/10 min, more preferably 6.0 g/10 min, further preferably 5.4 g/10 min, and particularly preferably 4.5 g/10 min. When it is 7.0 g/10 min or less, the thickness uniformity is good.

The lower limit of the melting point of the polyethylene resin contained in the polyethylene resin composition constituting the heat seal layer is preferably 85° C., more preferably 90° C., even more preferably 100° C., and particularly preferably 110° C. If it is 85° C. or higher, the surface protrusions do not sink and the anti-blocking function can be properly exhibited, resulting in good blocking resistance and slippage. In addition, the particles made of the polyethylene resin support the contact between the films, resulting in excellent scratch resistance.
The upper limit of the melting point of the polyethylene resin contained in the polyethylene resin composition constituting the heat seal layer is preferably 125° C., more preferably 120° C., and even more preferably 117° C. When it is 125° C. or lower, low-temperature sealability is good.

The polyethylene resin may be a single system, but two or more polyethylene resins with different densities can also be blended as long as they are within the density range described below. When two or more polyethylene resins with different densities are blended, the average density and blend ratio can be estimated by GPC measurement or density measurement.

The lower limit of the density range of the polyethylene resin contained in the polyethylene resin composition constituting the heat seal layer is preferably 900 kg/m ³ , more preferably 904 kg/m ³ , still more preferably 910 kg/m ³ , and particularly preferably 915 kg/m ^3. If it is 900 kg/m ³ or more, the bag has excellent firmness and is easy to process into bags.
The upper limit of the density range of the polyethylene resin contained in the polyethylene resin composition constituting the heat seal layer is preferably 930 kg/m ³ , more preferably 927 kg/m ³ , even more preferably 923 kg/m ³ , and particularly preferably 920 kg/m ^3. If it is 930 kg/m ³ or less, the heat seal initiation temperature is not high and the transparency is excellent. The density of the polyethylene resin contained in the polyethylene resin composition constituting the heat seal layer is preferably smaller than the density of the polyethylene resin contained in the polyethylene resin composition constituting the laminate layer described later. This makes it easier to achieve both transparency and stiffness of the polyethylene resin film.

When a polyethylene resin having a density of 900 kg/m3 or ^more is used, the particles made of the polyethylene resin can easily control the arithmetic mean roughness SRa of the surface of the heat seal layer to 200 nm or less and the maximum peak height SRmax to 9 μm or less, and can easily improve the transparency and stiffness.
In addition, when a polyethylene resin having a density of 930 kg/m3 or ^less is used, the particles made of polyethylene resin make it easy to make the arithmetic mean roughness SRa of the surface of the heat seal layer 60 nm or more and the maximum peak height SRmax 2 μm or more, and the polyethylene resin film is easy to obtain slipperiness, blocking resistance and scratch resistance, so that wrinkles and bumps are unlikely to occur during coating processing, printing processing and bag making processing, and transparency is also easy to maintain. In particular, the blocking resistance is unlikely to fluctuate between the measured values of each of the three measurements, and is stable. This is presumably because, when polyethylene having a density of 930 kg/m3 or ^less and particles made of polyethylene resin are melt-mixed, the viscosity average molecular weight of the particles made of polyethylene resin is unlikely to decrease, and the particle size is unlikely to change due to entanglement of molecular chains with polyethylene resin other than the particles made of polyethylene resin, and as a result, protrusions on the surface are likely to be formed.

As the above-mentioned polyethylene resin having a density of 900 to 930 kg/ ^m3 , a high-pressure low-density polyethylene (LDPE) that is transparent, highly flexible, and has excellent tear strength and tensile strength on average, a linear short-chain branched polyethylene (LLDPE) that is copolymerized with a small amount of butene-1, hexene-1, and/or octene-1, has many short molecular chains in the molecular chain, and has excellent sealing performance and physical strength, and a metallocene-catalyzed linear short-chain branched polyethylene (LLDPE) that shows a very sharp molecular weight distribution, has a uniform distribution of comonomers, and has excellent tear, tensile, puncture strength, and pinhole resistance properties can be selected according to the application. From the viewpoint of heat seal strength and sealability as a packaging material, it is preferable that the polyethylene resin is a linear low-density polyethylene. In addition, by introducing a plant-derived high-pressure low-density polyethylene or a plant-derived linear low-density polyethylene, the environmental load can be reduced.
As the polyethylene resin used in the heat seal layer, commercially available products can be used, and examples thereof include Umerit 2040FC, 0540FA, and 3540FC manufactured by Ube Maruzen Polyethylene Co., Ltd., Sumikathene E FV402 and FV405 manufactured by Sumitomo Chemical Co., Ltd., NC564A manufactured by Japan Polyethylene Co., Ltd., and SLH218 manufactured by Braskem.

The lower limit of the weighted average density of the polyethylene resin composition constituting the heat seal layer is preferably 900 kg/m ³ , more preferably 904 kg/m ³ , even more preferably 910 kg/m ³ , and particularly preferably 915 kg/m ^3. If it is 900 kg/m ³ or more, it is excellent in firmness and easy to process into bags. The upper limit of the weighted average density of the polyethylene resin constituting the heat seal layer is preferably 930 kg/m ³ , more preferably 927 kg/m ³ , even more preferably 923 kg/m ³ , and particularly preferably 920 kg/m ^3. If it is 930 kg/m ³ or less, the heat seal initiation temperature is not high and the transparency is also excellent.

(Particles with an average particle size of 9 μm or more)
The polyethylene resin composition constituting the heat seal layer preferably contains particles having an average particle diameter of 9 μm or more. By containing particles having an average particle diameter of 9 μm or more, large protrusions are easily formed on the surface of the heat seal layer. Indices of large protrusions include the ten-point average roughness SRz and the maximum height SRmax. When the three-dimensional surface roughness SRa and the maximum protrusion height SRmax are large, it is easy to obtain sufficient slip properties and blocking resistance for film processing.

The lower limit of the content of particles having an average particle size of 9 μm or more in the polyethylene resin composition constituting the heat seal layer is preferably 1900 ppm by weight, more preferably 3000 ppm, even more preferably 4000 ppm, and even more preferably 5000 ppm. If it is 1900 ppm or more, blocking resistance of the heat seal surface is easily obtained.
The upper limit of the content of the particles made of polyethylene resin in the polyethylene resin composition constituting the heat seal layer is preferably 16000 ppm by weight, more preferably 15000 ppm, even more preferably 11000 ppm, and even more preferably 7000 ppm. When it is 16000 ppm or less, the number of protrusions on the heat seal surface is not too large, and transparency and low-temperature sealability are also likely to be improved.

The upper limit of the average particle size of the particles having an average particle size of 9 μm or more contained in the polyethylene resin composition constituting the heat seal layer is preferably 20 μm, more preferably 17 μm, and even more preferably 15 μm. If it is 20 μm or less, the three-dimensional surface roughness SRa and the maximum projection height SRmax of the heat seal layer do not become too large, and compared with the case where the same weight of particles made of polyethylene resin is added, the number of projections increases, so that it is easy to obtain sufficient slip property and blocking resistance for film processing.
In addition, it is preferable that the film does not contain particles with an average particle size of 30 μm or more. Even if the average particle size is 20 μm or less, if the film contains a certain amount of 10% or more particles with an average particle size of 30 μm or more, the maximum peak height of the film surface is likely to exceed 15 μm, and if this occurs, flickering will occur when the film surface is visually observed. In addition, particles with a size of 30 μm or more are not preferable because they look similar to gel-like defects and the quality is reduced.

Particles having an average particle diameter of 9 μm or more are preferably spherical. Spherical particles are less likely to be scratched by friction between films. Here, "spherical" means that the sphericity is 0.9 or more, and sphericity can be defined as the minor axis/major axis of a particle. In other words, the sphericity of particles having an average particle diameter of 9 μm or more is preferably 0.9 or more and 1 or less. Sphericity can be obtained by measuring the minor axis/major axis of 10 particles of the same type and calculating the average of the ratio for the 10 particles. If the sphericity of the particles made of polyethylene resin obtained in this manner is 0.9 or more, the particles made of polyethylene resin are spherical.

The particles having an average particle size of 9 μm or more are preferably particles made of a polyethylene resin, which is less likely to cause scratches due to friction between films, and has a smaller specific gravity than inorganic particles, so that a larger number of large protrusions can be formed even when the same weight is added.
Spherical inorganic particles and crosslinked organic particles with an average particle size of 9 μm or more have no corners and are less likely to cause scratches due to friction between films than non-spherical inorganic particles. However, because of their large particle size, the particle surface area in contact with the film surface becomes very large when film surfaces are rubbed together, making them more susceptible to scratches.
There is also concern that the film may easily fall off the surface and may easily produce smears at the die.

The upper limit of the total content of spherical inorganic particles and crosslinked organic particles having an average particle size of more than 9 μm contained in the polyethylene resin composition constituting the heat seal layer is preferably 1000 ppm, more preferably 700 ppm, even more preferably 500 ppm, even more preferably 200 ppm, particularly preferably 100 ppm, and most preferably 0 ppm. If it exceeds 1000 ppm, scratch resistance may be impaired.

(Particles with an average particle size of less than 9 μm)
The polyethylene resin composition constituting the heat seal layer preferably contains particles having an average particle diameter of less than 9 μm. By containing particles having an average particle diameter of less than 9 μm, small protrusions are easily formed on the surface of the heat seal layer. An index of small protrusions is the protrusion density in a region with a small slice level, such as a height of 250 nm from the reference plane. If the protrusion density is large, the slipperiness can be improved. By improving the slipperiness, it is possible to suppress wrinkles even when a rolled film product is rolled and transported by an automatic packaging machine or the like.

The lower limit of the content of particles having an average particle size of less than 9 μm contained in the polyethylene resin composition constituting the heat seal layer is preferably 3100 ppm by weight, more preferably 4000 ppm, even more preferably 4500 ppm, and still more preferably 6000 ppm. If it is 3100 ppm or more, the slipperiness of the heat seal surface is good and wrinkles during transport are unlikely to occur.
The particles having an average particle size of less than 9 μm may be any of inorganic particles, particles made of a polyethylene resin, and crosslinked organic particles.
The upper limit of the content of particles having an average particle size of less than 9 μm contained in the polyethylene resin composition constituting the heat seal layer is preferably 15,000 ppm, more preferably 10,000 ppm, and even more preferably 8,000 ppm by weight. When it is 15,000 ppm or less, scratch resistance is good.

The lower limit of the particles having an average particle size of less than 9 μm contained in the polyethylene resin composition constituting the heat seal layer is preferably 3 μm, more preferably 4 μm, and even more preferably 5 μm. If the particle size is 3 μm or more, the particles are less likely to sink to the film surface and are more likely to form protrusions, so that wrinkles are less likely to occur when the film is transported with a roll.
Particles having an average particle size of less than 9 μm are preferably spherical. If the particles are spherical, scratches due to friction between films are unlikely to occur. Here, "spherical" means that the sphericity is 0.9 or more, and the sphericity can be defined as the minor axis/major axis of the particle.

(Non-spherical particles)
Since non-spherical particles are likely to cause scratches due to friction between films, it is preferable that the content of such particles is small. Here, "non-spherical" means that the sphericity is less than 0.9, and the sphericity can be defined as the average value of the ratio of the minor axis to the major axis for 10 particles as described above.
The upper limit of the content of non-spherical inorganic particles contained in the polyethylene resin composition constituting the heat seal layer is preferably 2500 ppm, more preferably 1000 ppm, even more preferably 500 ppm, still more preferably 200 ppm, and particularly preferably 0 ppm. If it exceeds 2500 ppm, transparency and scratch resistance are likely to be impaired.
The upper limit of the content of non-spherical particles having an average particle size of 9 μm or more is preferably 500 ppm, more preferably 300 ppm, even more preferably 200 ppm, still more preferably 100 ppm, and particularly preferably 100 ppm. If it exceeds 500 ppm, transparency and scratch resistance are likely to be impaired.
The upper limit of the content of non-spherical particles having an average particle size of less than 9 μm is preferably 2500 ppm, more preferably 1500 ppm, even more preferably 1000 ppm, still more preferably 500 ppm, particularly preferably 200 ppm, and particularly preferably 0 ppm. If it exceeds 2500 ppm, transparency and scratch resistance are likely to be impaired.

(Spherical particles made of polyethylene resin)
The polyethylene resin composition constituting the heat seal layer contains spherical particles made of polyethylene resin, and the spherical particles made of polyethylene resin preferably have a viscosity average molecular weight of 1.5 million or more, more preferably 1.6 million or more, and even more preferably 1.7 million or more. Also, it is preferably 2.5 million or less, more preferably 2.4 million or less, and even more preferably 2.3 million or less.
When the viscosity average molecular weight of the spherical particles made of a polyethylene-based resin is within this range, it becomes possible to control the average particle size of the spherical particles made of a polyethylene-based resin, and by using it in combination with a polyethylene-based resin of a specific density, it is possible to set the three-dimensional surface roughness SRa of at least one surface of the heat seal layer to 60 nm or more and 200 nm or less, and the maximum peak height SRmax to 2 μm or more and 9 μm or less.
The reason is that the difference in molecular weight between the spherical particles made of polyethylene resin and the polyethylene resin other than the particles made of polyethylene resin is very large, so the molecules do not mix sufficiently, and it is easy for the spherical particles made of polyethylene resin to maintain a shape close to a sphere even in the film obtained by melt mixing and extrusion, and aggregation due to fusion or adhesion between particles does not occur easily, so it is presumed that protrusions with a controlled shape can be formed on the film surface. The viscosity average molecular weight of the particles can be measured by the following method. 10 mg of particles are placed in 20 ml of decalin (decahydronaphthalene) and stirred at 150 ° C for 2 hours to dissolve the particles. The solution is placed in a thermostatic bath at 135 ° C. and the fall time (t _s ) between the marked lines is measured using an Ubbelohde type viscometer. Similarly, measurements are also made when 5 mg of particles are placed. As a blank, the fall time (t _b ) of only decalin without particles is measured. The specific viscosity (η _sp /C) of the particles calculated according to the following formula is plotted to derive a linear equation of the concentration (C) and the specific viscosity (η _sp /C) of the particles, and the limiting viscosity (η) extrapolated to a concentration of 0 is calculated.
η _sp /C=(t _s /t _b −1)/0.1
The viscosity average molecular weight can be calculated from this intrinsic viscosity (η) according to the following formula.
Viscosity average molecular weight = 5.34×10 ⁴ η ^1.49

When the viscosity average molecular weight of the spherical particles made of polyethylene resin is 1,500,000 or more, in the case where the temperature during melt mixing with a polyethylene resin other than the spherical particles made of polyethylene resin is higher than the melting point peak of the spherical particles made of polyethylene resin, even under film production conditions of high shear or high draft ratio using a large extruder, decomposition due to heat or shear, fusion and aggregation of particles made of polyethylene resin, and changes in particle size and shape of the particles made of polyethylene resin due to partial compatibility with polyethylene resin other than the spherical particles made of polyethylene resin are unlikely to occur, so that protrusions with a controlled shape like inorganic particles or organic crosslinked resin particles can be easily formed, and not only the function as an antiblocking agent is sufficient, but also the appearance such as transparency, the mechanical strength of the film, or the heat sealability are unlikely to be affected.
Furthermore, it has been found that spherical particles made of polyethylene resin with a viscosity average molecular weight of 1.5 million or more have the property of being difficult to aggregate in polyethylene resin, but are difficult to fall off from the polyethylene resin near the film surface, a feature that inorganic particles and organic crosslinked resin particles do not have. When the viscosity average molecular weight is 1.5 million or more and 2.5 million or less, it becomes easy to make the average particle size 5 μm or more and 20 μm or less, and when the heat seal layer raw material is melt-mixed and extruded to form a film, it tends to be easy to form suitable film surface protrusions.
Furthermore, when the viscosity average molecular weight of the particles made of polyethylene resin is 1.5 million or more, the particles themselves have lubricating properties, which contributes to improving blocking resistance and slippage, and since the particles made of polyethylene resin are soft, it is believed that scratch resistance is also improved.

The resin hardness of the spherical particles made of polyethylene resin is preferably D70 or less. When the hardness is D70 or less, defects are less likely to occur in the laminated layers of the film, for example, the vapor deposition layer, and the barrier properties are less likely to decrease. The hardness is more preferably D68 or less. Furthermore, when the hardness of the particles made of polyethylene resin is D60 or more, the slipperiness is improved and is less likely to deteriorate even when exposed to heat during film processing. The resin hardness is preferably Shore D hardness, and Shore D hardness can be measured using a Type D Shore hardness tester in accordance with ASTM D2240.

The spherical particles made of polyethylene resin are preferably a homopolymer of ethylene monomer, a copolymer of ethylene monomer and α-olefin, or a mixture of these. Examples of α-olefins include propylene, butene-1, hexene-1, 4-methylpentene-1, octene-1, decene-1, etc.

The lower limit of the density of the polyethylene resin forming the spherical particles made of polyethylene resin is preferably 930 kg/m ³ , more preferably 935 kg/m ³ , and even more preferably 937 kg/m ^3. If it is 930 kg/m ³ or more, the particles are not too soft and the shape of the particles is not easily maintained during melt extrusion, so that blocking resistance is not easily reduced.
The upper limit of the density of the polyethylene resin forming the spherical particles made of polyethylene resin is preferably 950 kg/m ³ , more preferably 945 kg/m ³ , and even more preferably 942 kg/m ^3. If the density exceeds 950 kg/m ³ , not only will the particles be hard and scratch resistance will be easily reduced, but the affinity with the base polyethylene resin will decrease, so that there is a possibility that the resistance to falling off will decrease.

An example of a spherical particle made of a polyethylene resin is Mipelon PM200 (average particle size 10 μm, melting point 136° C., viscosity average molecular weight 1.8 million, 0% particle size exceeding 30 μm, resin hardness D65, density 940 kg/m ³ , ultra-high molecular weight polyethylene particles) manufactured by Mitsui Chemicals, Inc.

(Spherical inorganic particles)
Inorganic particles include those having shapes such as spheres, cubes, and amorphous shapes, but particles with regular shapes such as spherical particles and cubic particles are synthetic particles that are artificially produced.
Spherical inorganic particles such as synthetic silica have a relatively narrow particle size distribution and are nearly spherical in shape, which makes them highly dispersible in films. In addition, they have no corners, which makes them highly scratch-resistant, making them ideal.
Examples of spherical inorganic particles include those made of inorganic substances such as silica, calcium carbonate, zeolite, etc. Examples of spherical inorganic particles include Shilton JC-50 (spherical zeolite particles, average particle size 5.0 μm) manufactured by Mizusawa Chemical Industry Co., Ltd. and KMP-130-10 (spherical silica particles, average particle size 10 μm) manufactured by Shin-Etsu Silicon Co., Ltd.

(Spherical cross-linked organic particles)
Examples of the spherical crosslinked organic particles include those produced by crosslinking polymethyl acrylate resins. Examples of the spherical crosslinked organic particles include MBX-8 (spherical polymethyl methacrylate particles, average particle size 8 μm) manufactured by Sekisui Chemical Industry Co., Ltd. and SX-500H (spherical styrene-based particles, average particle size 5 μm) manufactured by Soken Chemical & Engineering Co., Ltd.

(Non-spherical inorganic particles)
The non-spherical inorganic particles are preferably made of inorganic substances such as silica, talc, calcium carbonate, diatomaceous earth, zeolite, etc. Non-spherical inorganic particles are mainly produced by crushing naturally collected particles. These particles have a high hardness compared to polyethylene resin films, and also have many corners, which tend to deteriorate scratch resistance.
Examples of non-spherical inorganic particles include calcium carbonate particles manufactured by Maruo Calcium Co., Ltd. (CUBE-50KAS (Mohs hardness 3, average particle size 5 μm)), zeolite particles obtained by pulverizing natural zeolite with a pin mill, and diatomaceous earth particles obtained by pulverizing diatomaceous earth with a pin mill.

The content of crosslinked organic particles in the polyethylene resin composition constituting the heat seal layer is preferably equal to or less than the amount of particles made of polyethylene resin from the viewpoints of suppressing die buildup and cost. In the polyethylene resin composition constituting the heat seal layer, it is most preferable not to contain crosslinked organic particles in order to obtain the maximum effect of adding particles made of polyethylene resin, such as scratch resistance and prevention of particle dropout, as in the case of inorganic particles.
The crosslinked organic particles referred to here are organic crosslinked particles typified by polymethyl acrylate resin, etc. Particles made of polyethylene resin are not included in the organic crosslinked particles.

The polyethylene resin composition constituting the heat seal layer preferably contains an organic lubricant (organic slipper). The film's slipperiness and anti-blocking effect are improved, and the film becomes easier to handle. The reason for this is believed to be that the organic lubricant bleeds out and is present on the film surface, thereby exerting a slipperiness effect and a mold release effect. Furthermore, it is preferable to add an organic lubricant that has a melting point above room temperature. Examples of organic lubricants include fatty acid amides and fatty acid esters. Specific examples include oleic acid amide, erucic acid amide, behenic acid amide, ethylene bis oleic acid amide, hexamethylene bis oleic acid amide, and ethylene bis stearic acid amide. These may be used alone, but it is preferable to use two or more of them in combination, as this maintains the slipperiness and anti-blocking effect even in harsh environments.

The lower limit of the total content of the organic lubricant in the polyethylene resin composition constituting the heat seal layer is preferably 500 ppm by weight, more preferably 1000 ppm, further preferably 1200 ppm, and particularly preferably 1500 ppm. If it is 500 ppm or more, the slipperiness is likely to be stable immediately after film formation.
The upper limit of the total content of the organic lubricant in the polyethylene resin composition constituting the heat seal layer is preferably 3000 ppm by weight, more preferably 2500 ppm. If it is 3000 ppm or less, it is not too slippery and is unlikely to whiten over time.

The polyethylene resin composition constituting the heat seal layer may contain a heat stabilizer, which can suppress defects such as gelation that occur due to deterioration of the resin caused by heat or oxidation during melt extrusion.
As the heat stabilizer, commercially available heat stabilizers and antioxidants can be used. Specific examples include BASF's hindered phenol-based antioxidant (Irganox 1010), BASF's phosphite treatment stabilizer (Irgafos 168), and Sumitomo Chemical's phenol-phosphorus-based antioxidant (Sumilizer GP). The heat stabilizer may be used alone or in combination of two or more kinds. In addition, commercially available polyolefin resins are often added during production, but may be additionally added by master batch or the like.

The concentration of the heat stabilizer in the polyethylene resin composition is preferably 1600 ppm or more, more preferably 1800 ppm or more, and even more preferably 2000 ppm or more, in total, relative to the heat seal layer. If it is less than the above, defects such as gels are likely to occur. The upper limit is preferably 5000 ppm, more preferably 4000 ppm, and even more preferably 3500 ppm, in total, relative to the heat seal layer. If it exceeds the above, the edge of the film roll may turn red, impairing the appearance.

The polyethylene resin composition constituting the heat seal layer may contain an appropriate amount of an antistatic agent, an antifogging agent, a neutralizing agent, a nucleating agent, a colorant, other additives, inorganic fillers, etc., as necessary, within the scope of the object of the present invention. An example of a neutralizing agent is calcium stearate.

These polyethylene resin particles, inorganic particles, organic lubricants, etc. can be added by known methods, such as by adding them via master batches or by adding them directly during melt extrusion.

(Laminate layer)
The laminate layer in the present invention is made of a polyethylene-based resin composition. The polyethylene-based resin composition mainly contains a polyethylene-based resin, and preferably also contains particles made of a polyethylene-based resin. The polyethylene-based resin composition preferably contains 50% by weight or more of a polyethylene-based resin, more preferably 70% by weight or more, and even more preferably 90% by weight or more. The upper limit of the content of the polyethylene-based resin contained in the polyethylene-based resin composition is not particularly limited, but for example, the polyethylene-based resin composition preferably contains 100% by weight or less of a polyethylene-based resin.
The lower limit of the thickness ratio of the laminate layer of the polyethylene resin film is preferably 12%, more preferably 18%. By making it 12% or more, good laminate strength can be achieved.
The upper limit of the thickness ratio of the laminate layer of the polyethylene resin film is preferably 50%, more preferably 40%, and further preferably 30%. By keeping it at 50% or less, the heat seal strength can be improved.

(Polyethylene resin of laminate layer)
The polyethylene resin contained in the polyethylene resin composition constituting the laminate layer in the present invention preferably contains a homopolymer of an ethylene monomer, a copolymer of an ethylene monomer and an α-olefin, or a mixture thereof, and more preferably contains a copolymer of an ethylene monomer and an α-olefin. The α-olefin preferably contains propylene, butene-1, hexene-1, 4-methylpentene-1, octene-1, decene-1, or the like, or a combination thereof, and more preferably contains butene-1, hexene-1, or a combination thereof. The polyethylene resin is preferably a linear low density polyethylene. An example of the linear low density polyethylene is linear short-chain branched polyethylene. The density of the linear low density polyethylene is preferably 900 to 945 kg/m ³ , and more preferably 910 to 945 kg/m ³ .

The lower limit of the melt flow rate (hereinafter sometimes referred to as MFR) of the polyethylene resin contained in the polyethylene resin composition constituting the laminate layer is preferably 1.5 g/10 min, more preferably 2.0 g/10 min, and further preferably 2.3 g/10 min. If it is 1.5 g/10 min or more, it is easy to process into a film by extrusion molding, and the viscosity average molecular weight of the particles made of the polyethylene resin is unlikely to decrease.
The upper limit of the MFR of the polyethylene resin contained in the polyethylene resin composition constituting the laminate layer is preferably 7.0 g/10 min, more preferably 6.0 g/10 min, further preferably 5.4 g/10 min, and particularly preferably 4.5 g/10 min. When it is 7.0 g/10 min or less, the thickness uniformity is good.

The lower limit of the melting point of the polyethylene resin contained in the polyethylene resin composition constituting the laminate layer is preferably 110° C., more preferably 115° C., and particularly preferably 122° C. When it is 110° C. or higher, the bag has excellent firmness and is easy to process into bags.
The upper limit of the melting point of the polyethylene resin contained in the polyethylene resin composition constituting the laminate layer is preferably 135° C., more preferably 130° C., and further preferably 127° C. When it is 135° C. or lower, curling is small and transparency is excellent.

The polyethylene resin may be a single system, but two or more polyethylene resins with different densities may be blended as long as they are within the density range described below. When two or more polyethylene resins with different densities are blended, the average density and blending ratio can be estimated by GPC measurement or density measurement.
The lower limit of the weighted average density of the polyethylene resin composition constituting the laminate layer is 910 kg/m ³ , more preferably 915 kg/m ³ , and further preferably 920 kg/m ^3. When it is 910 kg/m ³ or more, the bag has excellent firmness and is easy to process into bags.
The upper limit of the weighted average density of the polyethylene resin composition constituting the laminate layer is 945 kg/m ³ , more preferably 935 kg/m ³ , and even more preferably 930 kg/m ^3. When it is 945 kg/m ³ or less, curling is small and transparency is excellent.

The density of the polyethylene resin contained in the polyethylene resin composition constituting the laminate layer is preferably 910 kg/m ³ , more preferably 915 kg/m ³ , and even more preferably 920 kg/m ^3. The upper limit of the density of the polyethylene resin contained in the polyethylene resin composition constituting the laminate layer is preferably 945 kg/m ³ , more preferably 935 kg/m ³ , and even more preferably 930 kg/m ³ . As the polyethylene resin having a density of 910 to 945 kg/ ^m3 , a high-pressure low-density polyethylene (LDPE), which is transparent, highly flexible, and has excellent tear strength and tensile strength on average, a linear short-chain branched polyethylene (LLDPE), which is copolymerized with a small amount of butene-1, hexene-1, and/or octene-1, has many short molecular chains in the molecular chain, and has excellent sealing performance and physical strength, and a metallocene-catalyzed linear short-chain branched polyethylene (LLDPE), which shows a very sharp molecular weight distribution, has a uniform distribution of comonomers, and has excellent tear, tensile, puncture strength, and pinhole resistance properties, can be selected according to the application. From the viewpoint of heat seal strength and sealing properties as a packaging material, linear low-density polyethylene is preferable. In addition, by introducing plant-derived high-pressure low-density polyethylene or plant-derived linear low-density polyethylene, the environmental load can be reduced.
As the polyethylene resin used in the laminate layer, commercially available products can be used, and examples thereof include Yumerit 2040FA, 825CA, 4040FC, and 846CC manufactured by Ube Maruzen Polyethylene Co., Ltd., Sumikathene FV402, FV405, and FV407 manufactured by Sumitomo Chemical Co., Ltd., and SLH218 manufactured by Braskem.

When the heat seal layer satisfies the following requirements 1) and 2), the laminate layer preferably does not contain particles, but may contain particles within a range that does not impair the effects of the present invention.
1) The surface has protrusions, and when slice levels are set at 250 nm intervals from a reference surface, the protrusion density at a slice level with a height of 250 nm is 160 pieces/ ^mm2 or more.
2) The change in haze after the surface layers are abraded together 100 times with a load of 200 g is 3.0% or less.
However, if the heat seal layer does not satisfy either 1) or 2) above, it is preferred that the laminate layer satisfies the following 1) and 2).
1) The surface has protrusions, and when slice levels are set at 250 nm intervals from a reference surface, the protrusion density at a slice level with a height of 250 nm is 160 pieces/ ^mm2 or more.
2) The change in haze after the surface layers are abraded together 100 times with a load of 200 g is 3.0% or less.

(Particles with an average particle size of 9 μm or more)
The polyethylene resin composition constituting the laminate layer preferably contains particles having an average particle size of 9 μm or more. By containing particles having an average particle size of 9 μm or more, large protrusions are easily formed on the surface of the laminate layer. Indices of large protrusions include the ten-point average roughness SRz and the maximum height SRmax. When the three-dimensional surface roughness SRa and the maximum protrusion height SRmax are large, it is easy to obtain sufficient slip properties and blocking resistance for film processing.

The lower limit of the content of particles having an average particle size of 9 μm or more in the polyethylene resin composition constituting the laminate layer is preferably 1900 ppm by weight, more preferably 3000 ppm, even more preferably 4000 ppm, and even more preferably 5000 ppm. If it is 1900 ppm or more, blocking resistance of the heat seal surface is easily obtained.
The upper limit of the content of the particles made of polyethylene resin in the polyethylene resin composition constituting the laminate layer is preferably 16000 ppm by weight, more preferably 15000 ppm, even more preferably 11000 ppm, and even more preferably 7000 ppm. When it is 16000 ppm or less, the number of protrusions on the heat seal surface is not too large, and transparency and low-temperature sealability are also likely to be improved.

The upper limit of the average particle size of the particles having an average particle size of 9 μm or more contained in the polyethylene resin composition constituting the laminate layer is preferably 20 μm, more preferably 17 μm, and even more preferably 15 μm. If it is 20 μm or less, the three-dimensional surface roughness SRa and the maximum projection height SRmax of the laminate layer do not become too large, and compared with the case where the same weight of particles made of polyethylene resin is added, the number of projections increases, so that it is easy to obtain sufficient slip properties and blocking resistance for film processing.
In addition, it is preferable that the film does not contain particles with an average particle size of 30 μm or more. Even if the average particle size is 20 μm or less, if the film contains a certain amount of 10% or more particles with an average particle size of 30 μm or more, the maximum peak height of the film surface is likely to exceed 15 μm, and if this occurs, flickering will occur when the film surface is visually observed. In addition, particles with a size of 30 μm or more are not preferable because they look similar to gel-like defects and the quality is reduced.

Particles having an average particle diameter of 9 μm or more are preferably spherical. Spherical particles are less likely to be scratched by friction between films. Here, "spherical" means that the sphericity is 0.9 or more, and sphericity can be defined as the minor axis/major axis of a particle. In other words, the sphericity of particles having an average particle diameter of 9 μm or more is preferably 0.9 or more and 1 or less. Sphericity can be obtained by measuring the minor axis/major axis of 10 particles of the same type and calculating the average of the ratio for the 10 particles. If the sphericity of the particles made of polyethylene resin obtained in this manner is 0.9 or more, the particles made of polyethylene resin are spherical.

The particles having an average particle size of 9 μm or more are preferably particles made of a polyethylene resin, which is less likely to cause scratches due to friction between films, and has a smaller specific gravity than inorganic particles, so that a larger number of protrusions can be formed even when the same weight is added.
Spherical inorganic particles and crosslinked organic particles with an average particle size of 9 μm or more have no corners and are less likely to cause scratches due to friction between films than non-spherical inorganic particles. However, because of their large particle size, the particle surface area in contact with the film surface becomes very large when film surfaces are rubbed together, making them more susceptible to scratches.
There is also concern that the film may easily fall off the surface and may easily produce smears at the die.
The upper limit of the total content of spherical inorganic particles and crosslinked organic particles having an average particle size exceeding 9 μm contained in the polyethylene resin composition constituting the laminate layer is preferably 1000 ppm, more preferably 700 ppm, even more preferably 500 ppm, still more preferably 200 ppm, particularly preferably 100 ppm, and most preferably 0 ppm. If it exceeds 1000 ppm, scratch resistance may be impaired.

(Particles with an average particle size of less than 9 μm)
The polyethylene resin composition constituting the laminate layer preferably contains particles having an average particle diameter of less than 9 μm. By containing particles having an average particle diameter of less than 9 μm, small protrusions are easily formed on the surface of the laminate layer. An index of small protrusions is the protrusion density in an area with a small slice level, such as a height of 250 nm from the reference plane. If the protrusion density is large, the slipperiness can be improved. By improving the slipperiness, it is possible to suppress wrinkles even when a rolled film product is rolled and transported by an automatic packaging machine or the like.

The lower limit of the content of particles having an average particle size of less than 9 μm contained in the polyethylene resin composition constituting the laminate layer is preferably 3100 ppm by weight, more preferably 4000 ppm, even more preferably 4500 ppm, and even more preferably 6000 ppm. If it is 3100 ppm or more, the slipperiness of the heat seal surface is good and wrinkles during transport are unlikely to occur.
The particles having an average particle size of less than 9 μm may be any of inorganic particles, particles made of a polyethylene resin, and crosslinked organic particles.
The upper limit of the content of particles having an average particle size of less than 9 μm contained in the polyethylene resin composition constituting the laminate layer is preferably 15,000 ppm, more preferably 10,000 ppm, and even more preferably 8,000 ppm by weight. If it is 15,000 ppm or less, scratch resistance is good.

The lower limit of the particles having an average particle size of less than 9 μm contained in the polyethylene resin composition constituting the laminate layer is preferably 3 μm, more preferably 4 μm, and even more preferably 5 μm. If the particle size is 3 μm or more, the particles are less likely to sink to the film surface, and the slipperiness is more likely to cause protrusions, so that wrinkles are less likely to occur when the roll is transported.
Particles having an average particle size of less than 9 μm are preferably spherical. If the particles are spherical, scratches due to friction between films are unlikely to occur. Here, "spherical" means that the sphericity is 0.9 or more, and the sphericity can be defined as the minor axis/major axis of the particle.

(Non-spherical particles)
Since non-spherical particles are prone to scratches due to friction between films, it is preferable to reduce the content of such particles. Here, "non-spherical" means that the sphericity is less than 0.9, and the sphericity can be defined as the average value of the ratio of the minor axis to the major axis of 10 particles as described above.
The upper limit of the content of non-spherical inorganic particles contained in the polyethylene resin composition constituting the laminate layer is preferably 2500 ppm, more preferably 1000 ppm, even more preferably 500 ppm, still more preferably 200 ppm, and particularly preferably 0 ppm. If the content exceeds 2500 ppm, transparency and scratch resistance are likely to be impaired.
The upper limit of the content of non-spherical particles having an average particle size of 9 μm or more is preferably 500 ppm, more preferably 300 ppm, even more preferably 200 ppm, still more preferably 100 ppm, and particularly preferably 100 ppm. If it exceeds 500 ppm, transparency and scratch resistance are likely to be impaired.
The upper limit of the content of non-spherical particles having an average particle size of less than 9 μm is preferably 2500 ppm, more preferably 1500 ppm, even more preferably 1000 ppm, still more preferably 500 ppm, particularly preferably 200 ppm, and particularly preferably 0 ppm. If it exceeds 2500 ppm, transparency and scratch resistance are likely to be impaired.

(Spherical particles made of polyethylene resin)
The polyethylene resin composition constituting the laminate layer contains spherical particles made of a polyethylene resin, and the spherical particles made of the polyethylene resin preferably have a viscosity average molecular weight of 1.5 million or more, more preferably 1.6 million or more, and even more preferably 1.7 million or more. Also, the viscosity average molecular weight is preferably 2.5 million or less, more preferably 2.4 million or less, and even more preferably 2.3 million or less.
When the viscosity average molecular weight of the spherical particles made of polyethylene-based resin is within this range, it becomes possible to control the average particle diameter of the spherical particles made of polyethylene-based resin, and by using it in combination with a polyethylene-based resin of a specific density, it is possible to set the three-dimensional surface roughness SRa of at least one surface of the laminate layer to 60 nm or more and 200 nm or less, and the maximum peak height SRmax to 2 μm or more and 9 μm or less.
The reason for this is believed to be that the difference in molecular weight between the spherical particles made of polyethylene-based resin and polyethylene-based resin other than the particles made of polyethylene-based resin is very large, so the molecules do not mix sufficiently, and even in the film obtained by melt mixing and extrusion, the spherical particles made of polyethylene-based resin easily maintain a shape close to spherical, and aggregation due to fusion or adhesion between particles is unlikely to occur, making it possible to form protrusions with controlled shape on the film surface.

When the viscosity average molecular weight of the spherical particles made of polyethylene resin is 1,500,000 or more, in the case where the temperature during melt mixing with a polyethylene resin other than the spherical particles made of polyethylene resin is higher than the melting point peak of the spherical particles made of polyethylene resin, even under film production conditions of high shear or high draft ratio using a large extruder, decomposition due to heat or shear, fusion and aggregation of particles made of polyethylene resin, and changes in particle size and shape of the particles made of polyethylene resin due to partial compatibility with polyethylene resin other than the spherical particles made of polyethylene resin are unlikely to occur, so that protrusions with a controlled shape like inorganic particles or organic crosslinked resin particles can be easily formed, and not only the function as an antiblocking agent is sufficient, but also the appearance such as transparency, the mechanical strength of the film, or the heat sealability are unlikely to be affected.
Furthermore, it has been found that spherical particles made of polyethylene resin with a viscosity average molecular weight of 1.5 million or more have the property of being difficult to aggregate in polyethylene resin, but are difficult to fall off from the polyethylene resin near the film surface, a feature that inorganic particles and organic crosslinked resin particles do not have. When the viscosity average molecular weight is 1.5 million or more and 2.5 million or less, it becomes easy to make the average particle size 5 μm or more and 20 μm or less, and when the laminate layer raw material is melt-mixed and extruded to form a film, it tends to be easy to form suitable film surface protrusions.
Furthermore, when the viscosity average molecular weight of the particles made of polyethylene resin is 1.5 million or more, the particles themselves have lubricating properties, which contributes to improving blocking resistance and slippage, and since the particles made of polyethylene resin are soft, it is believed that scratch resistance is also improved.

The resin hardness of the spherical particles made of polyethylene resin is preferably D70 or less. When the hardness is D70 or less, defects are less likely to occur in the laminated layers of the film, for example, the vapor deposition layer, and the barrier properties are less likely to decrease. The hardness is more preferably D68 or less. Furthermore, when the hardness of the particles made of polyethylene resin is D60 or more, the slipperiness is improved and is less likely to deteriorate even when exposed to heat during film processing. The resin hardness is preferably Shore D hardness, and Shore D hardness can be measured using a Type D Shore hardness tester in accordance with ASTM D2240.

The spherical particles made of polyethylene resin are preferably a homopolymer of ethylene monomer, a copolymer of ethylene monomer and α-olefin, or a mixture of these. Examples of α-olefins include propylene, butene-1, hexene-1, 4-methylpentene-1, octene-1, decene-1, etc.

The lower limit of the density of the polyethylene resin forming the spherical particles made of polyethylene resin is preferably 930 kg/m ³ , more preferably 935 kg/m ³ , and even more preferably 937 kg/m ^3. If it is 930 kg/m ³ or more, the particles are not too soft and the shape of the particles is not easily maintained during melt extrusion, so that blocking resistance is not easily reduced.
The upper limit of the density of the polyethylene resin particles forming the spheres made of polyethylene resin is preferably 950 kg/m ³ , more preferably 945 kg/m ³ , and even more preferably 942 kg/m ^3. If the density exceeds 950 kg/m ³ , not only will the particles be hard and scratch resistance will be easily reduced, but the affinity with the base polyethylene resin will decrease, so that there is a possibility that the resistance to falling off will decrease.

An example of a spherical particle made of a polyethylene resin is Mipelon PM200 (average particle size 10 μm, melting point 136° C., viscosity average molecular weight 1.8 million, proportion of particles with a particle size exceeding 30 μm is 0%, resin hardness D65, density 940 kg/m ³ , ultra-high molecular weight polyethylene particles) manufactured by Mitsui Chemicals, Inc.

(Spherical inorganic particles)
Inorganic particles include those having shapes such as spheres, cubes, and amorphous shapes, but particles with regular shapes such as spherical particles and cubic particles are synthetic particles that are artificially produced.
Spherical inorganic particles such as synthetic silica have a relatively narrow particle size distribution and are nearly spherical in shape, which makes them highly dispersible in films. In addition, they have no corners, which makes them suitable for improving scratch resistance.
Examples of spherical inorganic particles include those made of inorganic substances such as silica, calcium carbonate, zeolite, etc. Examples of spherical inorganic particles include Shilton JC-50 (spherical zeolite particles, average particle size 5.0 μm) manufactured by Mizusawa Chemical Industry Co., Ltd. and KMP-130-10 (spherical silica particles, average particle size 10 μm) manufactured by Shin-Etsu Silicon Co., Ltd.

(Spherical cross-linked organic particles)
Examples of the spherical crosslinked organic particles include those produced by crosslinking polymethyl acrylate resins. Examples of the spherical crosslinked organic particles include MBX-8 (spherical polymethyl methacrylate particles, average particle size 8 μm) manufactured by Sekisui Chemical Industry Co., Ltd. and SX-500H (spherical styrene-based particles, average particle size 5 μm) manufactured by Soken Chemical & Engineering Co., Ltd.

(Non-spherical inorganic particles)
The non-spherical inorganic particles are preferably made of inorganic substances such as silica, talc, calcium carbonate, diatomaceous earth, zeolite, etc. Non-spherical inorganic particles are mainly produced by crushing naturally collected particles. These particles have a high hardness compared to polyethylene resin films, and also have many corners, which tend to deteriorate scratch resistance.
Examples of non-spherical inorganic particles include calcium carbonate particles manufactured by Maruo Calcium Co., Ltd. (CUBE-50KAS (Mohs hardness 3, average particle size 5 μm)), zeolite particles obtained by pulverizing natural zeolite with a pin mill, and diatomaceous earth particles obtained by pulverizing diatomaceous earth with a pin mill.

The polyethylene resin composition that constitutes the laminate layer may or may not contain an organic lubricant, but it is preferable not to add one, as organic lubricants that bleed out onto the laminate surface can impair the adhesive strength of the laminate.

The polyethylene resin composition constituting the laminate layer may contain a heat stabilizer, which can suppress defects such as gelation that occur due to deterioration of the resin caused by heat or oxidation during melt extrusion.
Commercially available heat stabilizers and antioxidants can be used. Specific examples include BASF's hindered phenol-based antioxidant (Irganox 1010), BASF's phosphite treatment stabilizer (Irgafos 168), and Sumitomo Chemical's phenol-phosphorus-based antioxidant (Sumilizer GP). Heat stabilizers may be used alone or in combination of two or more. In addition, commercially available polyolefin resins are often added during production, but may also be added additionally using a master batch or the like.
The lower limit of the concentration of the heat stabilizer in the polyethylene resin composition is preferably 1600 ppm or more, more preferably 1800 ppm or more, and even more preferably 2000 ppm or more, in total, relative to the laminate layer. If it is less than the above, defects such as gels are likely to occur. The upper limit is preferably 5000 ppm, more preferably 4000 ppm, and even more preferably 3500 ppm, in total, relative to the laminate layer. If it exceeds the above, the end surface of the film roll may turn red, impairing the appearance.

The polyethylene resin composition constituting the laminate layer may contain an appropriate amount of antistatic agent, antifogging agent, neutralizing agent, nucleating agent, colorant, other additives, etc., as necessary, within the scope of the object of the present invention. An example of a neutralizing agent is calcium stearate.

These polyethylene resin particles, inorganic particles, organic lubricants, etc. can be added by known methods, such as by adding them via master batches or by adding them directly during melt extrusion.

It is preferable to activate the surface of the laminate layer of the polyethylene resin film by a method such as corona treatment. This improves the lamination strength with the base film.

(Core layer)
The polyethylene resin film preferably has a core layer between the laminate layer and the heat seal layer. The core layer is suitable for increasing the thickness of the film while suppressing costs and increasing the feeling of stiffness. The core layer is preferably made of a polyethylene resin composition. The polyethylene resin composition mainly contains a polyethylene resin and may contain particles made of a polyethylene resin. The polyethylene resin composition preferably contains 50% by weight or more of a polyethylene resin, more preferably 70% by weight or more, and even more preferably 90% by weight or more. On the other hand, the polyethylene resin composition preferably contains 100% by weight or less of a polyethylene resin.
The lower limit of the thickness ratio of the core layer of the polyethylene resin film is not particularly limited, but is preferably 30%, more preferably 40%. By making it 30% or more, good heat seal strength can be exhibited.
The upper limit of the thickness ratio of the core layer of the polyethylene resin film is preferably 80%, more preferably 70%, and further preferably 65%. By setting it to 80% or less, a good feeling of stiffness can be obtained.

(Polyethylene Resin of Core Layer)
The polyethylene resin constituting the core layer in the present invention preferably contains a homopolymer of an ethylene monomer, a copolymer of an ethylene monomer and an α-olefin, or a mixture thereof, and more preferably contains a copolymer of an ethylene monomer and an α-olefin. The α-olefin preferably contains propylene, butene-1, hexene-1, 4-methylpentene-1, octene-1, decene-1, or a combination thereof, and more preferably contains butene-1, hexene-1, or a combination thereof. The polyethylene resin is preferably a linear low density polyethylene. Examples of the linear low density polyethylene include linear short-chain branched polyethylene. The density of the linear low density polyethylene is preferably 900 to 945 kg/m ³ , and more preferably 910 to 930 kg/m ³ .

The lower limit of the melt flow rate (hereinafter sometimes referred to as MFR) of the polyethylene resin contained in the polyethylene resin composition constituting the core layer is preferably 1.5 g/10 min, more preferably 2.0 g/10 min, and further preferably 2.3 g/10 min. If it is 1.5 g/10 min or more, it is easy to process into a film by extrusion molding, and a decrease in the viscosity average molecular weight of the particles made of the polyethylene resin is unlikely to occur.
The upper limit of the MFR of the polyethylene resin contained in the polyethylene resin composition constituting the core layer is preferably 7.0 g/10 min, more preferably 6.0 g/10 min, further preferably 5.4 g/10 min, and particularly preferably 4.5 g/10 min. When it is 7.0 g/10 min or less, the thickness uniformity is good.

The lower limit of the melting point of the polyethylene resin contained in the polyethylene resin composition constituting the core layer is 100° C., more preferably 104° C., even more preferably 110° C., and particularly preferably 114° C. When the melting point is 100° C. or higher, the bag has excellent firmness and is easy to process into bags.
The upper limit of the melting point of the polyethylene resin contained in the polyethylene resin composition constituting the core layer is preferably 130° C., more preferably 127° C., and even more preferably 124° C. When it is 130° C. or lower, low-temperature sealability is good.

The polyethylene resin may be a single system, but two or more polyethylene resins with different densities may be blended as long as they are within the density range described below. When two or more polyethylene resins with different densities are blended, the average density and blending ratio can be estimated by GPC measurement or density measurement.
The lower limit of the weighted average density of the polyethylene resin composition constituting the core layer is preferably 910 kg/m ³ , more preferably 912 kg/m ³ , and even more preferably 915 kg/m ^3. When it is 910 kg/m ³ or more, the bag has excellent firmness and is easy to process into bags.
The upper limit of the weighted average density of the polyethylene resin composition constituting the core layer is preferably 930 kg/m ³ , more preferably 927 kg/m ³ , and further preferably 925 kg/m ^3. When it is 930 kg/m ³ or less, the heat seal initiation temperature is not high and the transparency is excellent.

The lower limit of the density of the polyethylene resin contained in the polyethylene resin composition constituting the core layer is preferably 910 kg/m ³ or less, more preferably 912 kg/m ³ or less, and even more preferably 915 kg/m ³ or less. If it is 910 kg/m ³ or more, the waist is excellent and bag manufacturing is easy. The upper limit of the density of the polyethylene resin contained in the polyethylene resin composition constituting the core layer is preferably 930 kg/m ³ or less, more preferably 927 kg/m ³ or less, and even more preferably 925 kg/m ³ or less. As the polyethylene resin having a density of 910 to 930 kg/ ^m3 , a high-pressure low-density polyethylene (LDPE), which is transparent, highly flexible, and has excellent tear strength and tensile strength on average, a linear short-chain branched polyethylene (LLDPE), which is copolymerized with a small amount of butene-1, hexene-1, and/or octene-1, has many short molecular chains in the molecular chain, and has excellent sealing performance and physical strength, and a metallocene-catalyzed linear short-chain branched polyethylene (LLDPE), which shows a very sharp molecular weight distribution, has a uniform distribution of comonomers, and has excellent tear, tensile, puncture strength, and pinhole resistance properties, can be selected according to the application, but linear low-density polyethylene is preferable from the viewpoint of heat seal strength and sealability as a package. In addition, by introducing plant-derived high-pressure low-density polyethylene or plant-derived linear low-density polyethylene, the environmental load can be reduced.

The plant-derived polyethylene resin can be produced by, for example, a high-pressure method, a solution method, a gas-phase method, or the like, using ethanol derived from sugarcane or corn as a raw material. Examples of the α-olefin include a copolymer of plant-derived ethylene and at least one α-olefin having 3 or more carbon atoms. The α-olefin may be derived from a fossil fuel as long as it is generally called an α-olefin, and is preferably an α-olefin having 3 to 12 carbon atoms, such as propylene, butene-1, hexene-1, octene-1, or 4-methyl-1-pentene. Examples of the copolymer of ethylene and an α-olefin include an ethylene-hexene-1 copolymer, an ethylene-butene-1 copolymer, and an ethylene-octene-1 copolymer, and from the viewpoint of bending pinhole resistance, an ethylene-hexene copolymer is preferred. The lower limit of the plant-derived carbon content in the plant-derived polyethylene resin is preferably 50% by weight, more preferably 80% by weight. If it is 50% by weight or more, the carbon dioxide reduction effect is good. The upper limit is preferably 100% by weight.
As the polyethylene resin used in the core layer, commercially available products can be used, and examples thereof include Yumerit 2040FA and 825CA manufactured by Ube Maruzen Polyethylene Co., Ltd., Sumikathene E FV402 and FV405 manufactured by Sumitomo Chemical Co., Ltd., NC564A manufactured by Japan Polyethylene Co., Ltd., and SLH218 manufactured by Braskem.

In this case, particles made of the above-mentioned polyethylene resin, inorganic particles, or crosslinked organic particles may or may not be added to the core layer, but since the presence of large particles such as coarse particles makes lamination prone to occur, it is preferable not to intentionally add them, except for particles contained in the raw materials from which the product is recycled.

The polyethylene resin composition constituting the core layer may or may not contain an organic lubricant. Examples of organic lubricants include fatty acid amides and fatty acid esters. Specific examples include oleic acid amide, erucic acid amide, behenic acid amide, ethylene bis oleic acid amide, hexamethylene bis oleic acid amide, and ethylene bis stearic acid amide. These may be used alone, but it is preferable to use two or more types in combination, as this can maintain lubricity and anti-blocking effects even in harsh environments.

The lower limit of the total content of the organic lubricant in the polyethylene resin composition constituting the core layer is not particularly limited, but is preferably 100 ppm or more.
The upper limit of the total content of the organic lubricant in the polyethylene resin composition constituting the core layer is preferably 3000 ppm, more preferably 2500 ppm. If it is 3000 ppm or less, the surface is not too slippery and is not easily whitened over time.

By adding pellets made from recycled semi-finished products generated during the manufacturing process and finished film products to the core layer, the resin can be reused without compromising heat seal strength, reducing the environmental impact. In addition, the organic lubricant contained in the pellets can supplement the organic lubricant in the core layer.

The polyethylene resin composition constituting the core layer may contain a heat stabilizer, which can suppress defects such as gelation that occur due to deterioration of the resin caused by heat or oxidation during melt extrusion.
Commercially available heat stabilizers and antioxidants can be used. Specific examples include BASF's hindered phenol-based antioxidant (Irganox 1010), BASF's phosphite treatment stabilizer (Irgafos 168), and Sumitomo Chemical's phenol-phosphorus-based antioxidant (Sumilizer GP). Heat stabilizers may be used alone or in combination of two or more. In addition, commercially available polyolefin resins are often added during production, but may also be added additionally using a master batch or the like.
The lower limit of the concentration of the heat stabilizer in the polyethylene resin composition is preferably 1600 ppm or more, more preferably 1800 ppm or more, and even more preferably 2000 ppm or more, in total, relative to the core layer. If it is less than the above, defects such as gels are likely to occur. The upper limit is preferably 5000 ppm, more preferably 4000 ppm, and even more preferably 3500 ppm, in total, relative to the core layer. If it exceeds the above, the end surface of the film roll may turn red, impairing the appearance.

The polyethylene resin composition constituting the core layer may contain an appropriate amount of an antistatic agent, an antifogging agent, a neutralizing agent, a nucleating agent, a colorant, other additives, inorganic fillers, etc. in any layer as necessary, within the scope of the object of the present invention. An example of a neutralizing agent is calcium stearate.

These polyethylene resin particles, inorganic particles, organic lubricants, etc. can be added by known methods, such as by adding them via master batches or by adding them directly during melt extrusion.

(Method for producing polyethylene resin film)
As a specific method for forming the layers in this way, a general multi-layering device (such as a multi-layer feed block, a static mixer, or a multi-layer multi-manifold) can be used. For example, a method can be used in which thermoplastic resins discharged from different flow paths using two or more extruders are laminated in multiple layers using a field block, a static mixer, a multi-manifold die, or the like. It is also possible to use only one extruder and introduce the above-mentioned multi-layering device into the melt line from the extruder to the T-die.

The polyethylene resin film can be formed by, for example, inflation or T-die, but the T-die is preferred for increasing transparency and thickness variation. The inflation method uses air as a cooling medium, whereas the T-die method uses a cooling roll, making it an advantageous manufacturing method for increasing the cooling rate of the unstretched sheet. By increasing the cooling rate, crystallization of the unstretched sheet can be suppressed, resulting in high transparency.
In addition, since the molding can be performed stably, the thickness variation rate in the longitudinal direction and the width direction is good. For these reasons, the molding using the T-die method is more preferable.
As a lamination method by T-die coextrusion, a general multi-layering device (such as a multi-layer feed block, a static mixer, or a multi-layer multi-manifold) can be used. For example, a method in which thermoplastic resins discharged from different flow paths using two or more extruders are laminated into multiple layers using a field block, a static mixer, a multi-manifold die, or the like can be used.
It is also possible to use only one extruder and install the above-mentioned multi-layering device in the melt line from the extruder to the T-die.
The screw of the extruder may be a single screw or a twin screw, but from the viewpoint of production speed, a single screw is preferred.
The upper limit of the outlet temperature of the metering section of the extruder, the melt line, and the die is preferably 280° C., more preferably 270° C. If the temperature exceeds 280° C., the deterioration of the resin will progress faster, and foreign matter such as gels will tend to increase. The lower limit of the outlet temperature of the metering section of the extruder, the melt line, and the die is preferably 160° C., more preferably 180° C. If the temperature is 160° C. or lower, unmelted resin may be discharged, or the filter in the melt line may become clogged.

The lower limit of the cooling roll temperature when casting the molten raw resin to obtain a sheet is preferably 15°C, and more preferably 20°C. If it is less than the above, condensation will occur on the cooling roll, causing insufficient adhesion between the unstretched sheet and the cooling roll, which may cause thickness defects. The upper limit of the cooling roll is preferably 80°C, more preferably 60°C, and even more preferably 50°C. If it is 80°C or less, the transparency of the polyethylene resin film is less likely to deteriorate.

Because both ends of the polyethylene resin sheet become thicker due to necking, it is preferable to use a cutter or similar tool to trim them. This allows the corona treatment to be applied evenly and also stabilizes the winding process.

The lower limit of the power density of the corona treatment applied to the laminate surface is preferably 15 W·min/ ^m2 , more preferably 17 W·min/ ^m2 . If it is 15 W·min/m2 or ^less , the laminate strength and printability may decrease. The upper limit is preferably 30 W·min/ ^m2 , more preferably 25 W·min/ ^m2 . If it is ³⁰ W·min/m2 or more, strike-through may occur, causing roll blocking.

The lower limit of the film-forming speed is preferably 8 m/min, and more preferably 15 m/min. If it is less than 8 m/min, the rotation speed of the cooling roll and the like will not be stable, and thickness variations will tend to be large. The upper limit of the film-forming speed is preferably 300 m/min, and more preferably 250 m/min. If it exceeds 300 m/min, the sheet transport will be unstable and wrinkles will tend to occur.

The wound sheet can be cut by a slitting machine. This allows efficient production of product rolls of any width. The lower limit of the winding speed of the slitting machine is preferably 30 m/min, and more preferably 50 m/min. If it is less than 30 m/min, cutting may not be able to keep up with the film production speed. The upper limit of the film production speed is preferably 300 m/min, and more preferably 250 m/min. If it exceeds 300 m/min, the sheet transport becomes unstable and wrinkles are likely to occur.

(Characteristics of polyethylene resin film)
The "longitudinal direction" of a polyethylene resin film is the direction corresponding to the flow direction in the film production process, and the "width direction" is the direction perpendicular to the flow direction in the film production process.
For polypropylene film whose flow direction in the film manufacturing process is unknown, wide-angle X-rays are incident perpendicularly to the film surface, and the scattering peak originating from the (110) plane of the α-type crystal is scanned in the circumferential direction. The direction with the greatest diffraction intensity in the obtained diffraction intensity distribution is defined as the "longitudinal direction," and the direction perpendicular to this is defined as the "width direction."

(Protrusion density at a height of 250 nm from the reference surface of surface roughness)
The protrusion density at a height of 250 nm from the reference plane of the surface roughness of a polyethylene resin film is the number of protrusions per ^mm2 (pieces/mm2) when slice levels are set at 250 nm intervals from the reference plane in a roughness curve obtained by measuring the three-dimensional roughness with a three-dimensional surface roughness meter. The reference plane is a reference position (height ⁰ nm) determined when the entire measurement area is leveled after the three-dimensional surface roughness measurement, and then a cutoff is performed using a specified filter to remove components such as noise, waviness, and shape. The reference plane preferably corresponds to the center position of the movable range of the stylus in the thickness direction of the polyethylene resin film.
The protrusion density at each slice level is a parameter derived from particle analysis (multiple levels) described in the measurement method described later. The protrusion density is a value calculated from the number of cut ends of the protrusions when the film surface is cut horizontally on the convex side at a slice level of a specified height. The measurement method is performed as described in the examples, and when slice levels are set at 250 nm intervals from the reference plane, a slice level of 250 nm in height refers to a surface 250 nm from the reference plane toward the outside of the film in the thickness direction.
The lower limit of the protrusion density at a height of 250 nm from the reference plane of the surface roughness of at least one surface of the polyethylene resin film is 160 protrusions/ ^mm2 , preferably 200 protrusions/ ^mm2 , and more preferably 250 protrusions/ ^mm2 . If it is less than 160 protrusions/ ^mm2 , the slipperiness of the laminate surface and the heat seal surface of the film is poor, and wrinkles are likely to occur when the film is rolled and transported.
The upper limit of the protrusion density at a height of 250 nm from the reference plane of the surface roughness of at least one surface of the polyethylene resin film is not particularly limited, but is preferably 1000 pieces/ ^mm2 , more preferably 700 pieces/ ^mm2 , and even more preferably 600 pieces/ ^mm2 . By making it 1000 pieces/ ^mm2 or less, transparency and scratch resistance are improved.

(Arithmetic mean roughness SRa)
The arithmetic mean roughness SRa of a polyethylene-based resin film is calculated by dividing the volume of the area surrounded by the roughness curved surface and the central plane by the measurement range, with the X-axis and Y-axis being orthogonal coordinate axes placed on the central plane of the roughness curved surface and the Z-axis being perpendicular to the central plane, and expressing the unevenness of that section as an average value.
The lower limit of the arithmetic mean roughness SRa of at least one surface of the polyethylene resin film is preferably 60 nm, more preferably 65 nm, and even more preferably 70 nm. When it is 60 nm or more, the film has excellent slip properties and blocking resistance.
The upper limit of the arithmetic mean roughness SRa of at least one surface of the polyethylene resin film is preferably 200 nm, more preferably 180 nm, and even more preferably 150 nm. If it is 200 nm or less, the transparency is not easily reduced and the scratch resistance is excellent. The measurement method is the method described in the examples.

(Maximum height SRmax)
The maximum height SRmax of the polyethylene resin film is the distance between two planes parallel to the average plane of the curved surface.
The lower limit of the maximum surface height SRmax of at least one side of the polyethylene resin film is preferably 2.0 μm, more preferably 4.0 μm, and further preferably 5.0 μm. When it is 2.0 μm or more, the film has excellent slip properties and blocking resistance.
The upper limit of the maximum surface height SRmax of at least one side of the present polyethylene resin film is preferably 9.0 μm, more preferably 8.0 μm. If it exceeds 9.0 μm, it is not preferable because it causes poor appearance. The measurement method is the method described in the examples.

(Ten-point average roughness SRz)
The ten-point average roughness SRz is the distance between the average height of the fifth highest peak and the average depth of the fifth deepest peak with respect to the average surface of the curved surface.
The lower limit of the ten-point average roughness SRz of at least one surface of the polyethylene resin film is preferably 3000 nm, more preferably 3900 nm, and further preferably 4500 nm. When it is 3000 nm or more, the film has excellent slip properties and blocking resistance.
The upper limit of the ten-point average roughness SRz of at least one surface of the polyethylene resin film is preferably 15000 nm, more preferably 10000 nm, and even more preferably 7000 nm. If it is 15000 nm or less, the transparency is not easily reduced and the scratch resistance is excellent. The measurement method is the method described in the examples.

(Static friction coefficient)
The lower limit of the static friction coefficient between the heat-sealed surfaces of the polyethylene resin film is preferably 0.05, more preferably 0.08, and even more preferably 0.13. If it is 0.05 or more, the film is less likely to meander when processed into a roll.
The upper limit of the static friction coefficient between the heat-sealed surfaces of the polyethylene resin film is preferably 0.70, more preferably 0.50, even more preferably 0.40, and particularly preferably 0.30. If it is 0.70 or less, the inner surfaces tend to slide easily against each other when filling the package with food or when opening the package, making it easy to open.
The lower limit of the static friction coefficient between the heat seal surface and the laminate surface of the polyethylene resin film is preferably 0.10, more preferably 0.20, and even more preferably 0.30. If it is 0.10 or more, the film roll is unlikely to collapse during transportation.
The upper limit of the static friction coefficient between the heat seal surface and the laminate surface of the polyethylene resin film is preferably 0.70, more preferably 0.60, and even more preferably 0.50. If it is 0.70 or less, the product film in a roll shape is less likely to wrinkle even when it is rolled and transported.

(Accelerated Blocking Strength)
The smaller the accelerated blocking strength between the heat-sealed surfaces of the polyethylene-based resin film, the more preferable. The upper limit of the accelerated blocking strength between the heat-sealed surfaces of the polyethylene-based resin film is preferably 300 mN/70 mm, more preferably 200 mN/70 mm or less, and even more preferably 150 mN/70 mm. If it exceeds 300 mN/70 mm, the powder-free property, the opening property of the bag, etc. may not be sufficiently obtained.

(Scratch resistance)
The scratch resistance refers to the amount of change in haze after rubbing the polyethylene resin film surfaces of a laminate of a biaxially oriented nylon film (15 μm) and a polyethylene resin film together. When the polyethylene resin film surfaces are overlapped, it is preferable to overlap the heat seal layer and the heat seal layer. Alternatively, when the polyethylene resin film surfaces are overlapped, the heat seal layer and the laminate layer may be overlapped, or the laminate layer and the laminate layer may be overlapped.
The scratch resistance is evaluated as the change in haze after 100 times of abrasion with a load of 200g applied to the polyethylene resin film surfaces stacked together as described in the examples below. Specifically, cut out two samples with a length of 180mm and a width of 50mm, and measure the haze before abrasion. Next, stack the polyethylene resin film surfaces of the two samples facing each other, set them in a Gakushin abrasion tester manufactured by Yasuda Seiki, and after 100 times of abrasion with a load of 200g, measure the haze at the same position as that before abrasion, and obtain the change in haze before and after abrasion.
The increase in haze of the polyethylene resin film of the present invention before and after scratching is preferably 3.0% or less, more preferably 2.0% or less, even more preferably 1.0% or less, and particularly preferably 0.5% or less. The increase in haze before and after scratching is ideally 0%, but may be 0.01% or more, 0.05% or more, 0.1% or more, etc. in practice.

(Hayes)
The lower limit of the haze of the polyethylene resin film is preferably 1.0%, more preferably 2.0%, further preferably 3.0%, and particularly preferably 4.0%. If the haze is 1.0% or more, the film surface is not extremely uneven, and therefore blocking of the inner surface of the package is unlikely to occur.
The upper limit of the haze of the polyethylene resin film is preferably 15.0%, more preferably 13.0%, even more preferably 10.0%, and still more preferably 8.0%. When it is 15.0% or less, visibility of the package is easily obtained.

(Wrinkles during transportation)
The manufactured film is generally wound into a roll before being transported, stored, and used. The rolled-up product may be transported by machine or by hand. In particular, when packaging is performed using an automatic packaging machine, the film is rotated or rolled by the machine more frequently. In such a process, if the machine applies a local force to the body of the roll, the force may cause wrinkles in the film roll (transport wrinkles). If transport wrinkles occur, wrinkle marks will appear in the laminate or package, deteriorating the appearance. For this reason, it is preferable that transport wrinkles do not occur.
As a result of intensive research into this phenomenon, it was surprisingly found that the occurrence of conveyance wrinkles can be reduced by having fine protrusions on at least one side of the film. It is presumed that the presence of fine protrusions on the film improves the slipperiness of the front and back sides of the film, and makes it possible to disperse the force applied by the machine during conveyance. The fine protrusions can be expressed as the protrusion density at a height of 250 μm from the reference plane as mentioned above, and can be achieved by appropriately selecting the particle shape and amount of the antiblocking agent added.

(Young's Modulus)
The lower limit of the Young's modulus (in the longitudinal direction) of the polyethylene resin film is preferably 60 MPa, more preferably 70 MPa. If it is less than this, the film may be too weak and difficult to process.
The upper limit of the Young's modulus (longitudinal direction) of the polyethylene resin film is preferably 600 MPa, more preferably 500 MPa, and further preferably 400 MPa.
The lower limit of the Young's modulus (width direction) of the polyethylene resin film is preferably 60 MPa, more preferably 70 MPa. If it is less than the above, the film may be too weak and difficult to process.
The upper limit of the Young's modulus (width direction) of the polyethylene resin film is preferably 600 MPa, more preferably 500 MPa, and further preferably 400 MPa.
The longitudinal direction refers to the flow direction (MD direction) of the equipment when the film is manufactured, and the width direction refers to the direction perpendicular to the longitudinal direction (TD direction).

(Thermal shrinkage rate)
The lower limit of the thermal shrinkage rate in the longitudinal direction of the polyethylene resin film is preferably 0.2%, more preferably 0.3%, and further preferably 0.5%. If it is 0.2% or more, the heat resistance is sufficient.
The upper limit of the thermal shrinkage rate of the polyethylene resin in the longitudinal direction is preferably 2.5%, more preferably 1.5%. If it is 2.5% or less, pitch deviation during printing is unlikely to occur.
The lower limit of the heat shrinkage rate in the width direction of the polyethylene resin film is preferably 0.0%, more preferably 0.1%, and further preferably 0.2%. If it is 0.0% or more, the film is less likely to elongate when heated.
The upper limit of the heat shrinkage rate of the polyethylene resin film in the width direction is preferably 1.5%, more preferably 1.0%. If it is 1.5% or less, pitch deviation during printing is unlikely to occur.

(Tear strength)
The lower limit of the tear strength (longitudinal direction) of the polyethylene resin film is preferably 1.0 N, more preferably 2.0 N. If it is less than the above, the package may be easily torn.
The upper limit of the tear strength (longitudinal direction) of the polyethylene resin film is preferably 8.0 N, more preferably 6.0 N, and further preferably 5.0 N. If it is 8.0 N or less, the package is easy to open.
The lower limit of the tear strength (width direction) of the polyethylene resin film is preferably 1.0 N, more preferably 2.0 N. If it is less than the above, the package may be easily torn.
The upper limit of the tear strength (width direction) of the polyethylene resin film is preferably 8.0 N, more preferably 6.0 N, and further preferably 5.0 N. If it is 8.0 N or less, the package is easy to open.

(Wet tension)
The lower limit of the wetting tension of the corona-treated surface (lamination surface) of the polyethylene resin film is preferably 30 mN/m, more preferably 35 mN/m. If it is 30 mN/m or more, the laminate strength is unlikely to decrease.
The upper limit of the wet tension of the polyethylene resin film is preferably 55 mN/m, more preferably 50 mN/m. If it is 55 mN/m or less, blocking between films is unlikely to occur when the polyethylene resin film is wound on a roll.

(Heat seal initiation temperature for film alone)
The lower limit of the heat seal initiation temperature of the polyethylene resin film alone is preferably 80° C., more preferably 90° C. When it is 80° C. or higher, the film has a high stiffness and is easy to handle.
The upper limit of the heat seal initiation temperature of the polyethylene resin film is preferably 140° C., more preferably 130° C., and further preferably 120° C. If the temperature is 140° C. or less, the package can be produced at high speed, which is economically advantageous. The heat seal initiation temperature is greatly affected by the melting point of the heat seal layer.

(Biomass ratio)
The biomass degree indicates the ratio of carbon atoms derived from plants to the total carbon atoms in the film. The higher the ratio of carbon atoms derived from plants, the greater the carbon dioxide reduction effect based on the idea of carbon neutrality. The lower limit of the biomass degree of the polyethylene resin film may be 0%, but is preferably 10%, and more preferably 15%. If it is 10% or more, the carbon dioxide reduction effect is large. The upper limit of the biomass degree of the polyethylene resin film is not particularly limited, but is preferably 70%, more preferably 55% or less, and even more preferably 40%. If it is 70% or less, foreign matter due to plant-derived raw materials is unlikely to increase, the appearance is good, and the filter in the extrusion process is unlikely to increase in pressure.

(Structure of laminate and manufacturing method)
In an embodiment, the laminate includes at least one film selected from the group consisting of a uniaxially oriented polyolefin resin film, a biaxially oriented polyolefin resin film, a uniaxially oriented polyamide resin film, a biaxially oriented polyamide resin film, a uniaxially oriented polyester resin film, and a biaxially oriented polyester resin film, and the polyethylene resin film. The laminate preferably includes the polyethylene resin film as a sealant, and includes at least one film selected from the group consisting of a polyamide resin film, a polyester resin film, and a polyolefin resin film as a base film. In addition, as a known technique, a coating or deposition process may be applied to these base films or sealants for the purpose of imparting adhesiveness or barrier properties, or an aluminum foil may be further laminated. The base film is preferably selected from biaxially oriented films such as a biaxially oriented polyolefin resin film, a biaxially oriented polyamide resin film, and a biaxially oriented polyester resin film, but may also be a uniaxially oriented film.
Specific examples include biaxially oriented PET (polyethylene terephthalate) film/aluminum foil/sealant, biaxially oriented PET (polyethylene terephthalate) film/sealant, biaxially oriented nylon film/sealant, biaxially oriented polypropylene film/sealant, biaxially oriented polyethylene terephthalate (PET) film/biaxially oriented nylon film/sealant, uniaxially oriented polyethylene film/sealant, etc. As a lamination method, a known method such as a dry lamination method or an extrusion lamination method can be used, and any lamination method may be used.

The properties of the laminate according to the embodiment will be described below.
(Heat seal strength)
The lower limit of the heat seal strength of the laminate containing the polyethylene resin film at 160°C, 0.2 MPa, 1 sec is preferably 40 N/15 mm, more preferably 50 N/15 mm, and even more preferably 55 N/15 mm. If it is 40 N/15 mm or more, it is easy to obtain bag breakage resistance. If the heat seal strength is 60 N/15 mm, it is very excellent, and if it is 70 N/15 mm, it is sufficient.

(Package)
The polyethylene resin film or the laminate arranged to wrap around the contents, such as foodstuffs, for the purpose of protecting the contents from dust, gas, etc. in the natural world, is called a package. The package is preferably made of the laminate described above. The package is manufactured by cutting out the polyethylene resin film or the laminate, bonding the inner surfaces together with a heated heat seal bar or ultrasonic waves, and forming it into a bag shape. For example, a four-sided sealed bag in which two rectangular sheets are stacked with the heat seal layer side on the inside and the four sides are heat sealed, or a back-sealed packaging bag is widely used. The contents may be foodstuffs, but may also be other products such as daily necessities, and the shape of the package may be a shape other than a rectangle, such as a standing pouch or a pillow package.

This application claims the benefit of priority based on Japanese Patent Application No. 2023-135022, filed on August 22, 2023. The entire contents of the specification of Japanese Patent Application No. 2023-135022, filed on August 22, 2023, are incorporated by reference into this application.

The present invention will be described in detail below with reference to examples, but is not limited to these. The properties obtained in each example were measured and evaluated by the following methods. In the evaluation, the flow direction of the film in the film production process was defined as the longitudinal direction (MD direction), and the direction perpendicular to the flow direction was defined as the width direction (TD direction).

(1) Resin density, weighted average density Density was evaluated according to JIS K7112: 1999 D method (density gradient pipe). Measurements were performed with N=3, and the average value was calculated. The weighted average density of the resin composition in each layer was determined by averaging the densities of the resins constituting the resin composition, with the weight of each resin as the weight.

(2) Melt flow rate (MFR)
The measurement was carried out in accordance with JIS K-7210-1 at 190° C. and a load of 2.16 kg. N=3 was measured, and the average value was calculated.

(3) Melting point The melting point was determined as the temperature of the maximum melting peak in the DSC curve of the resin obtained using a Shimadzu Differential Scanning Calorimeter DSC-60 manufactured by Shimadzu Corporation. The starting temperature was 30° C., the heating rate was 5° C./min, and the end temperature was 180° C. Measurements were performed with N=3, and the average value was calculated.

(4) Sphericity of particles The surface of the film was observed with a 3D laser microscope (LEXT OLS4100) manufactured by OLYMPAS Corporation, and the short diameter and long diameter of the particles were measured. The objective lens was selected at 50x. The ratio of short diameter/long diameter was calculated. The same measurement was performed for 10 particles of the same type, and the average of the ratios for the 10 particles was calculated, which was taken as the sphericity. In addition, the average of the long diameters for the 10 particles of the same type was calculated, which was taken as the average particle size.

(5) Hardness of Particles The hardness of particles made of polyethylene resin was measured using a resin sheet prepared by melting particles made of polyethylene resin, using a Shore hardness tester type D in accordance with ASTM D2240.
The hardness of the inorganic particles was determined by calculating the Mohs hardness of the mineral before crushing from the Mohs hardness table. Specifically, the mineral before crushing was rubbed against standard substances in order of hardness from the lowest to the highest, and the hardness of the measured object was judged by visually checking whether the measured object was scratched or not.

(6) Protrusion density at a height of 250 nm from the reference plane of surface roughness For the measurement data under the conditions of the three-dimensional high-precision fine shape measuring instrument detailed in (7) below, a three-dimensional surface roughness analysis system (type iFace model TDA-31) was used, and "Particle analysis (multiple levels)" was selected in the analysis tab of the menu bar, and the "Output content setting" was set to "Mountain particles: numerical output," the "Hysteresis width" item was set to 0.005 μm, and the "Slice level equal interval" item was set to 0.25 μm (250 nm) to calculate the mountain particle distribution, and the protrusion number density (pieces/mm ² ) for each protrusion height (level 0.25 μm (250 nm) increments) was obtained. That is, the protrusion number density (pieces/mm ² ) at each of the protrusion heights 0 nm, 250 nm, 500 nm, 750 nm, ... was obtained.

(7) Arithmetic mean roughness SRa, maximum height SRmax, ten-point mean roughness SR
The three-dimensional roughness of the heat seal surface of a polyethylene resin film was measured under the following measurement conditions based on JIS-B0601 (1994). After processing under the following analysis conditions, the arithmetic mean roughness SRa, maximum height SRmax, and ten-point mean roughness SRz were selected from the "3D roughness parameters" in the analysis tab of the menu bar, and the values were determined by outputting them in list format.

(Measurement conditions)
Measurement device: Three-dimensional high-precision micro-shape measuring instrument (model ET-4000A) manufactured by Kosaka Laboratory Co., Ltd. Stylus: Tip radius 0.5 μmR, diameter 2 μm, made of diamond Stylus pressure: 100 μN
Measurement direction: Longitudinal direction of film Measurement length on X-axis (longitudinal direction of film): 1.0 mm
- Y-axis (film width direction) measurement length: 0.20 mm
・X-axis feed speed: 0.1 mm/s (measurement speed)
- Y-axis feed pitch: 2 μm (measurement interval)
- Number of Y-axis lines: 101 (number of measurements)
・Z-axis measurement magnification: 20,000 times (vertical magnification)
(Analysis conditions)
・Analysis software: 3D surface roughness analysis system (model TDA-31)
Leveling: Yes, all areas Low cutoff: 0.200 mm (waviness cutoff value)
Low frequency spare length: λc x 0
High cutoff: 0.000 mm
- High frequency reserve length: None

(8) Static friction coefficient A sample was cut out from the polyethylene resin film with a size of 200 mm in the longitudinal direction and 80 mm in the width direction, and fixed on the table of the testing machine with the measurement surface facing up. Next, a sample was cut out from the polyethylene resin film with a size of 90 mm in the longitudinal direction and 70 mm in the width direction, and fixed to a sliding piece weighing 1.0 kg and with a bottom surface of 70 mm in length and 50 mm in width so that the measurement surface was on the outside. The measurement surfaces of the two samples were placed face to face and overlapped, and measurements were performed. A universal tensile tester STM-T-50BP (manufactured by Toyo Baldwin) was used to measure in accordance with JIS K7125. As the measurement surfaces, the heat-sealed surfaces were placed face to face, or the heat-sealed surface and the laminated surface were placed face to face, and each was evaluated.

(9) Accelerated blocking strength A polyethylene resin film was cut into a length of 148 mm and a width of 105 mm. The heat seal surface and the laminate surface were placed face to face and overlapped. After preheating for 30 minutes in a 50°C environment, the sample was sandwiched between 7.0 cm square aluminum plates held at 50°C. Using a mini test press MP-SCH manufactured by Toyo Seiki Seisakusho Co., Ltd., the aluminum plate and the sample were pressed under conditions of 50°C and 100 kN and held for 15 minutes. The removed sample was cut into a width of 70 mm. The overlapped sample was opened by 30 mm, and a metal rod with a diameter of 3 mm was inserted so as to be parallel to the width direction. The sample was mounted on an autograph AG-I manufactured by Shimadzu Corporation, and the load was measured when the metal rod was moved in the length direction at a condition of 200 mm/min. Measurements were performed with N=3, and the average value was calculated.

(10) Scratch resistance Two samples measuring 180 mm in the longitudinal direction and 50 mm in the transverse direction were cut out from each laminate obtained in the Examples and Comparative Examples, and were stacked with the heat seal layer surfaces facing each other, and were set in a Gakushin abrasion tester manufactured by Yasuda Seiki, and the haze change after 100 abrasions was evaluated with a load of 200 g. The haze was measured at the center of the film (a point was drawn at the edge, and points were drawn at both ends that do not affect the haze measurement from the opposite side of the abraded surface) before setting it on the abrasion table, and the haze was measured at the same position after abrasion to obtain the difference.

(11) Haze Haze was measured using NDH8000 manufactured by Nippon Denshoku Co., Ltd. in accordance with JIS K7136. Measurements were made on the polyolefin resin film before lamination (N=3), and the average value was calculated.

(12) Wrinkles during transport A polyethylene resin film was wound up to a width of 1000 mm and a length of 4000 m, and the end of the film at the unwound portion of the roll was taped in three places. A K-liner paper was wrapped around the surface of the obtained film roll. The film roll was rolled and transported onto a roller conveyor where rolls were arranged at 20 cm intervals, and the film roll was rotated once on the roller conveyor. The K-liner paper was removed from the roller conveyor, and the surface of the film roll was visually confirmed. Ten film rolls were evaluated. Based on the following index, those marked with ○ were deemed to have passed.
◯: No wrinkles were generated in any of the 10 film rolls, and the film was not deformed.
Δ: Some film rolls had wrinkles, but the deformation marks disappeared when 10 m of the surface film was unwound.
x: The film roll was wrinkled, deformed beyond 10 m from the surface, and some of the film rolls had marks.

(13) Young's modulus The tensile strength in the longitudinal direction and the transverse direction was measured at 23° C. in accordance with JIS-K7127. The test piece had a length of 150 mm and a width of 15 mm, and the test speed was 200 mm/min. N=3 was measured, and the average value was calculated.

(14) Heat shrinkage rate Measured according to JIS Z1712 by the following method. The film was cut into pieces of 20 mm x 200 mm along the longitudinal direction or the transverse direction of the film, and was hung in a hot air oven at 90°C for 30 minutes. The length after heating was measured, and the heat shrinkage rate in the longitudinal direction and the transverse direction was calculated as the ratio of the shrunken length to the original length.

(15) Tear strength Tear strength was measured according to JIS K7128-1:1998. The tear strength of the polyethylene resin film was evaluated. The test speed was 200 mm/min. Measurements were performed in the longitudinal direction and the width direction with N=3, and the average value was calculated.

(16) Wet Tension The wet tension of the laminate layer surface was measured according to JIS K6768 Plastics - Films and Sheets - Wet Tension Test Method.

(17) Heat seal initiation temperature The heat seal initiation temperature of the polyethylene resin film was measured in accordance with JIS Z 1713 (2009). At this time, the film was cut into a rectangular test piece (for heat seal) of 50 mm x 250 mm (width direction x length direction of the film). The heat seal layer parts of two test pieces were overlapped, and a heat gradient tester (heat seal tester) manufactured by Toyo Seiki Seisakusho Co., Ltd. was used, and the heat seal pressure was 0.2 MPa and the heat seal time was 1.0 sec. In the measurement of the film alone, the film was protected with a biaxially oriented polyester resin film so that the resin would not adhere to the heat seal bar, and then heat sealed. The heat seal temperature was increased from 80 ° C. in order to obtain multiple test pieces. After heat sealing, a sample with a width of 15 mm was cut out from each test piece. Each sample fused by heat sealing was opened at 180 °, and the unsealed part was sandwiched with a zipper and the sealed part was peeled off. The test machine used was a universal material testing machine 5965 manufactured by Instron Instruments. The test speed was 200 mm/min. The values were plotted on a graph paper with the heat seal temperature on the horizontal axis and the peel load on the vertical axis, and the plots were connected with straight lines. Then, the average value (N=5) of the heat seal temperatures of the samples at which the peel load reached 4.9 N on the straight line was calculated, and the average value was taken as the heat seal start temperature. Five measurements were taken, and the average value (N=5) was calculated.

(18) Heat seal strength The heat seal conditions and strength measurement conditions are as follows. That is, two samples were cut out from each laminate obtained in the examples and comparative examples, the polyethylene resin film sides were overlapped, and heat sealed at a pressure of 0.2 MPa for 1 second with a seal bar width of 10 mm and a heat seal temperature of 160°C, and then allowed to cool. A test piece of 80 mm in the longitudinal direction and 15 mm in the transverse direction was cut out from the heat-sealed film, and the peel strength of the test piece was measured when the heat-sealed part was peeled off at a crosshead speed of 200 mm/min. The test machine used was a universal material testing machine 5965 manufactured by Instron Instruments. Measurements were performed with N=3 for each, and the average value was calculated.

(19) Biomass Degree Based on the ASTM D6866 Biobased Test, the biomass degree was calculated from the C14 (carbon atom having a mass number of 14) concentration in the film.

Example 1
(Raw resin used)
LL-1: Umerit (registered trademark) 0540F manufactured by Ube Maruzen Polyethylene Co., Ltd. (metallocene-based 1-hexene copolymer linear low-density polyethylene, density 904 kg/m ³ , MFR 4.0 g/10 min, melting point 111° C.)
LL-2: Sumikathene (registered trademark) E FV402 manufactured by Sumitomo Chemical Co., Ltd. (metallocene catalyst-based 1-hexene copolymer LLDPE, density: 913 kg/m ³ , MFR: 3.8 g/10 min, melting point: 115° C.)
LL-3: Ube Maruzen Polyethylene Co., Ltd.'s Yumerit (registered trademark) 2040FA (metallocene-based 1-hexene copolymer linear low-density polyethylene, density 918 kg/m ³ , MFR 4.0 g/10 min, melting point 116° C.)
LL-4: Sumikathene (registered trademark) E FV405 manufactured by Sumitomo Chemical Co., Ltd. (metallocene catalyst-based 1-hexene copolymer LLDPE, density: 923 kg/m ³ , MFR: 3.8 g/10 min, melting point: 118° C.)
LL-5: SLH218 manufactured by Braskem (plant-derived linear low-density polyethylene, 1-hexene-1-butene copolymer, density 916 kg/m ³ , melting point 126° C., biomass content 90%)
LL-6: Ube Maruzen Polyethylene Co., Ltd.'s Yumerit (registered trademark) 846CC (metallocene-based 1-hexene copolymer linear low-density polyethylene, density 937 kg/m ³ , MFR 4.5 g/10 min, melting point 126° C.)
LL-7: Ube Maruzen Polyethylene Co., Ltd.'s Yumerit (registered trademark) 4040FC (metallocene-based 1-hexene copolymer linear low-density polyethylene, density 938 kg/m ³ , MFR 3.5 g/10 min, melting point 126° C.)
(Particle master batch)
MB-1: Sumikathene (registered trademark) E FV402 manufactured by Sumitomo Chemical was mixed with Mipelon PM200 (average particle size 10 μm, sphericity 0.91, melting point 136° C., density 940 kg/m ³ , viscosity average molecular weight 1.8 million, ratio of particles with a particle size exceeding 30 μm 0%, resin hardness D65, ultra-high molecular weight polyethylene particles) manufactured by Mitsui Chemicals, Inc. to prepare a master batch containing 15% by weight of PM200.
MB-2: Sumikathene (registered trademark) E FV402 manufactured by Sumitomo Chemical was mixed with Shilton JC-50 (spherical zeolite particles, average particle size 5.0 μm, sphericity 0.96) manufactured by Mizusawa Industrial Chemicals, Ltd. to prepare a master batch containing 15% by weight of JC-50.
MB-3: Sumikathene (registered trademark) E FV402 manufactured by Sumitomo Chemical was mixed with KMP-130-10 (spherical silica particles, average particle size 10 μm, sphericity 0.98) manufactured by Shin-Etsu Silicon Co., Ltd. to prepare a master batch containing 15% by weight of KMP-130-10.
MB-4: Sumikathene (registered trademark) E FV402 manufactured by Sumitomo Chemical was mixed with Dicalite WF manufactured by Grefco. Inc. (irregular diatomaceous earth, processed to an average particle size of 5 μm using a pin mill pulverizer, sphericity of 0.75) to prepare a master batch containing 15% by weight of Dicalite WF.
(Organic lubricant masterbatch)
MB-5: Erucamide was mixed with Sumikathene (registered trademark) E FV402 manufactured by Sumitomo Chemical to prepare a master batch containing 4% by weight of erucamide.
MB-6: Ethylene bis oleamide was mixed with Sumikathene (registered trademark) E FV402 manufactured by Sumitomo Chemical to prepare a master batch containing 2% by weight of ethylene bis oleamide.
MB-7: Sumikathene (registered trademark) E FV402 manufactured by Sumitomo Chemical was mixed with CUBE-50KAS (cubic calcium carbonate particles, Mohs hardness 3, average particle size 5 μm, sphericity 0.71) manufactured by Maruo Calcium Co., Ltd. to prepare a master batch containing 15% by weight of cubic calcium carbonate.

(Non-oriented polyethylene resin film)
Example 1
For the polyethylene resin film, the raw materials were adjusted based on the resin composition and ratio of each layer shown in Table 1 below. The raw materials were transported in fixed amounts by a screw feeder and weighed. One weighing batch was 14 kg for the laminate layer, 40 kg for the core layer, and 14 kg for the heat seal layer. Table 1 shows the evaluation results.

(Melt Extrusion)
The mixed raw materials for the core layer were introduced into a three-stage single-screw extruder with a screw diameter of 90 mm, and the mixed raw materials for the heat seal layer and the laminate layer were introduced into a three-stage single-screw extruder with a diameter of 65 mm and a three-stage single-screw extruder with a diameter of 45 mm, respectively, in the order of heat seal layer/core layer/laminate layer. In detail, the mixed raw materials were introduced into a T-slot die designed to have a width of 1400 mm, a two-stage preland, and a curved step portion so that the flow of the molten resin in the die was uniform, and the die outlet temperature was 230° C. The thickness ratios of the heat seal layer/core layer/laminate layer were 20%/60%/20%, respectively.

(cooling)
The molten resin sheet coming out of the die was cooled with a cooling roll at 40°C to obtain an unstretched polyethylene resin film having a thickness of 50 μm. When cooling with the cooling roll, both ends of the film on the cooling roll were fixed with an air nozzle, the entire width of the molten resin sheet was pressed against the cooling roll with an air knife, and at the same time, a vacuum chamber was operated to prevent air from being entrained between the molten resin sheet and the cooling roll. The air nozzles were installed in series in the film traveling direction at both ends. The die was surrounded by a sheet to prevent the molten resin sheet from being exposed to wind.
The direction of the suction port of the vacuum chamber was aligned with the traveling direction of the extruded sheet.
(trimming)
The edges of both ends of the cooled and solidified polyolefin resin film were cut off with a slit blade and introduced into a separate line.
(Corona treatment)
The surface of the laminate layer of the film was subjected to corona treatment (power density: 20 W·min/m ² ).

(Winding)
The film was formed at a speed of 40 m/min. The film was wound up while being pressed with a contact roll under tension to prevent wrinkles. After aging at 40° C. for 24 hours, both ends were cut again with a slitting machine, and the film was wound up to a length of 4000 m in a roll having a width of 1000 mm to obtain a film roll.

(Creation of Laminate)
The polyethylene resin film obtained in the examples and comparative examples and a biaxially oriented nylon film (manufactured by Toyobo Co., Ltd., N1102, thickness 15 μm) as a base film were coated with an ester adhesive obtained by mixing 33.6 parts by mass of a base agent (manufactured by Toyo Morton Co., Ltd., TM569), 4.0 parts by mass of a curing agent (manufactured by Toyo Morton Co., Ltd., CAT10L), and 62.4 parts by mass of ethyl acetate, so that the coating amount was 3.0 g/m ² , and dry laminated. This was wound up and kept at 40 ° C., and aged for 3 days to obtain a laminate.

(Examples 2 to 10)
A 50 μm polyethylene-based resin film was obtained in the same manner as in Example 1, except that the raw materials used for the heat seal layer, core layer, and laminate layer were changed to the ratios shown in Table 1. A laminate was obtained in the same manner as in Example 1. Table 1 shows the evaluation results.

(Example 11)
A polyethylene-based resin film having a thickness of 30 μm was obtained in the same manner as in Example 2, except that the total thickness of the film was 30 μm. The thickness ratios of the heat seal layer/core layer/laminate layer were 20%/60%/20%, respectively. A laminate was obtained in the same manner as in Example 1. The evaluation results are shown in Table 1.

(Comparative Examples 1 to 8)
In Example 1, the raw materials used for the heat seal layer, core layer, and laminate layer were changed to the ratios shown in Table 2, and a 30 μm polyethylene resin film was obtained in the same manner as in Example 1. A laminate was obtained in the same manner as in Example 1. Table 2 shows the evaluation results.

In Comparative Examples 1 and 2, since there were few fine protrusions, wrinkles were likely to occur during transport.
In Comparative Example 3, the amount of inorganic particles having an average particle size of 5 μm or less added was large, and therefore the scratch resistance was poor.
In Comparative Example 4, the amount of particles made of polyethylene resin and having an average particle size of 5 to 20 μm was too small, so that conveyance wrinkles were likely to occur.
In Comparative Example 5, the amount of particles made of polyethylene resin and having an average particle size of 5 to 20 μm was too large, and therefore the scratch resistance was poor.
In Comparative Example 6, the amount of particles having an average particle size exceeding 9 μm was too large, and therefore the scratch resistance was poor.
In Comparative Example 7, non-spherical inorganic particles were used, and therefore the scratch resistance was poor.
In Comparative Example 8, non-spherical inorganic particles were used, and therefore the scratch resistance was poor.

The above results are shown in Tables 1 and 2. In Tables 1 and 2, "spherical inorganic and crosslinked organic particles less than 9 μm" indicates the total amount of spherical inorganic particles less than 9 μm and spherical crosslinked organic particles less than 9 μm. In Tables 1 and 2, "spherical inorganic and crosslinked organic particles 9 μm or more" indicates the total amount of spherical inorganic particles 9 μm or more and spherical crosslinked organic particles 9 μm or more.

The present invention provides a polyethylene resin film that is excellent in scratch resistance, heat sealability, blocking resistance, and slipperiness. Such a polyethylene resin film can be used as a non-oriented polyethylene resin film that is less likely to wrinkle even when transported by rolling a film roll, making a significant contribution to industry.

Claims (10)

A polyethylene-based resin film having a heat seal layer made of a polyethylene-based resin composition on one surface layer and a laminate layer made of a polyethylene-based resin composition on the other surface layer, wherein at least one of the surface layers satisfies the following 1) and 2).
1) The surface layer has protrusions, and when slice levels are set at 250 nm intervals from a reference surface, the protrusion density at a slice level having a height of 250 nm is 160 pcs/ ^mm2 or more.
2) The change in haze after the surface layers are abraded together 100 times under a load of 200 g is 3.0% or less. The polyethylene resin film according to claim 1, wherein the weighted average density of the polyethylene resin composition constituting the heat seal layer is smaller than the weighted average density of the polyethylene resin composition constituting the laminate layer. The polyethylene resin film according to claim 1, wherein the heat seal layer contains spherical particles made of polyethylene resin, and the spherical particles made of polyethylene resin have a viscosity average molecular weight of 1.5 million or more and 2.5 million or less. 2. The polyethylene-based resin film according to claim ¹ , wherein the weighted average density of the polyethylene-based resin composition constituting the laminate layer is 910 kg/ ^m3 or more and 945 kg/m3 or less, and the weighted average density of the polyethylene-based resin composition constituting the heat seal layer is 900 kg/ ^m3 or more and 930 kg/ ^m3 or less. 2. The polyethylene-based resin film according to claim 1, wherein one or more core layers are present between the heat seal layer and the laminate layer, and the weighted average density of the polyethylene-based resin composition constituting the core layer is 910 kg/m3 or ^more and 930 kg/ ^m3 or less. The polyethylene resin film according to claim 1, wherein the polyethylene resin contained in the polyethylene resin composition constituting the laminate layer and the polyethylene resin contained in the polyethylene resin composition constituting the heat seal layer are linear low-density polyethylene. The polyethylene resin film according to claim 1, wherein the arithmetic mean roughness SRa of at least one of the surfaces of the laminate layer and the heat seal layer is 60 nm or more and 200 nm or less, and the maximum height SRmax is 2 μm or more and 9 μm or less. The polyethylene resin film according to claim 1, in which the change in haze after the heat seal layers are abraded 100 times with a load of 200 g is 3.0% or less. A laminate comprising at least one film selected from the group consisting of uniaxially oriented polyolefin resin films, biaxially oriented polyolefin resin films, uniaxially oriented polyamide resin films, biaxially oriented polyamide resin films, uniaxially oriented polyester resin films, and biaxially oriented polyester resin films, and the polyethylene resin film according to any one of claims 1 to 8. A package comprising the laminate according to claim 9.