Polyethylene film, packaging material, and package

Abstract

To provide a polyethylene film having enhanced barrier properties.SOLUTION: A polyethylene film comprises a film layer containing an ethylene polymer, and an inorganic material layer containing an inorganic material on the film layer, wherein, in accordance with JIS C2151:2019, the thermal shrinkage XMD100 in the MD direction when heated at 100°C for 15 minutes is less than 5.0%.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a polyethylene film, a packaging material, and a package. [Background technology]

[0002] Polyethylene film is known as an environmentally friendly packaging material.

[0003] Patent Document 1 describes a laminate that has an objective of providing a laminate that can realize packaging materials and the like that have strength and barrier properties that are applicable as packaging materials and also have excellent recyclability, and is characterized by comprising a substrate, an intermediate layer, and a heat-seal layer, the intermediate layer comprising a vapor-deposited film and a substrate main body, the substrate being a stretched resin film, the substrate main body being a stretched resin film, and the substrate, the substrate main body, and the heat-seal layer all being made of polyethylene. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2020-055158 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention provides a polyethylene film with improved barrier properties. [Means for solving the problem]

[0006] The present inventors have conducted extensive studies to solve the above-mentioned problems. As a result, they have found that there is a correlation between the heat shrinkage rate in the MD direction and the barrier properties of a polyethylene film comprising a film layer containing an ethylene-based polymer and an inorganic layer containing an inorganic material. Based on the above findings, the present inventors have conducted further extensive studies and found that the barrier properties of a polyethylene film can be improved by setting the heat shrinkage rate within a predetermined range, thereby completing the present invention.

[0007] That is, according to the present invention, there are provided the following polyethylene film, packaging material, and packaging body.

[0008] [1] a film layer containing an ethylene-based polymer; an inorganic layer containing an inorganic material on the film layer; Equipped with According to JIS C2151:2019, the heat shrinkage rate X in the MD direction when heated at 100°C for 15 minutes MD100 is less than 5.0%. [2] According to JIS C2151:2019, the thermal shrinkage rate X in the TD direction when heated at 100°C for 15 minutes TD100 and the heat shrinkage rate X MD100 The polyethylene film according to [1], wherein the absolute value of the difference between [3] The heat shrinkage rate X MD100 to the heat shrinkage rate X TD100 The polyethylene film according to [2], wherein the value obtained by subtracting [4] According to JIS C2151:2019, the thermal shrinkage rate X in the TD direction when heated at 100°C for 15 minutes TD100 The polyethylene film according to any one of [1] to [3], wherein the content of hydroxybenzoates is 0.0% or more. [5] According to JIS C2151:2019, the heat shrinkage rate X in the MD direction when heated at 120°C for 15 minutes MD120The polyethylene film according to any one of [1] to [4], wherein the modulus of elasticity is less than 26.0%. [6] According to JIS C2151:2019, the thermal shrinkage rate X in the TD direction when heated at 120°C for 15 minutes TD120 and the heat shrinkage rate X in the MD direction when heated at 120°C for 15 minutes in accordance with JIS C2151:2019. MD120 The polyethylene film according to any one of [1] to [5], wherein the absolute value of the difference between [7] According to JIS C2151:2019, the heat shrinkage rate X in the MD direction when heated at 120°C for 15 minutes MD120 According to JIS C2151:2019, the thermal shrinkage rate X in the TD direction when heated at 120°C for 15 minutes TD120 The polyethylene film according to any one of [1] to [6], wherein the value obtained by subtracting [8] According to JIS C2151:2019, the thermal shrinkage rate X in the TD direction when heated at 120°C for 15 minutes TD120 The polyethylene film according to any one of [1] to [7], wherein the content of hydroxybenzoates is 0.0% or more. [9] The polyethylene film according to any one of [1] to [8], wherein the total value of the tensile modulus of elasticity in the MD direction (T1) and the tensile modulus of elasticity in the TD direction (T2) measured in accordance with JIS K7127:1999 using a tensile tester under conditions of a measurement temperature of 23±2°C, 50±5% RH, and a tensile speed of 5 mm / min is 500 MPa or more and 9000 MPa or less.

[10] The moisture permeability measured by the following method is 3.2 g / (m 2 The polyethylene film according to any one of [1] to [9], wherein the temperature is 100°C (days) or less. (Measurement method) An adhesive is applied to one side of a 50 μm thick LLDPE film. The polyethylene film and the LLDPE film are then laminated together so that the inorganic layer side of the polyethylene film is in contact with the adhesive-coated side of the LLDPE film, yielding a multilayer film. The resulting multilayer film is then folded back so that the LLDPE film faces inward, and the two sides are heat-sealed to form a bag. Calcium chloride is then placed inside the resulting bag. The other side of the bag is then heat-sealed to reduce the surface area to 0.01 m. 2 The resulting bag is then stored at 40°C and 90% RH for 300 hours. The weight of the calcium chloride is measured before and after storage, and the moisture permeability is calculated from the difference.

[11] The oxygen permeability measured by the following method is 800mL / (m 2 The polyethylene film according to any one of [1] to

[10] , wherein the saturation temperature is 100°C / 240°F / day·MPa or less. (Measurement method) An adhesive is applied to one side of a 50 μm thick LLDPE film. Next, the polyethylene film and the LLDPE film are laminated together so that the inorganic layer side of the polyethylene film is in contact with the adhesive-coated side of the LLDPE film, thereby obtaining a multilayer film. The oxygen permeability (mL / (m 2 ·day·MPa)) is measured in accordance with JIS K7126:2006 under conditions of 20°C and 90% RH.

[12] The polyethylene film according to any one of [1] to

[11] , wherein the film layer includes a uniaxially stretched film layer or a biaxially stretched film layer.

[13] The polyethylene film according to any one of [1] to

[12] , wherein the content of the ethylene polymer in the film layer is 75% by mass or more and 100% by mass or less, when the entire film layer is taken as 100% by mass.

[14] The polyethylene film according to any one of [1] to

[13] , wherein the ethylene polymer contains polyethylene.

[15] The polyethylene film according to

[14] , wherein the polyethylene comprises one or more selected from the group consisting of low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), and high-density polyethylene (HDPE).

[16] The density of the ethylene polymer is 0.910 g / cm 3 More than 0.970g / cm 3 The polyethylene film according to any one of [1] to

[15] below.

[17] The polyethylene film according to any one of [1] to

[16] , further comprising a surface resin layer on at least one surface of the film layer.

[18] The polyethylene film according to

[17] , wherein the surface resin layer contains an ethylene-based polymer.

[19]

[18] The polyethylene film according to

[18] , wherein the content of the ethylene polymer in the surface resin layer is 75% by mass or more and 100% by mass or less, when the entire surface resin layer is taken as 100% by mass.

[20] The polyethylene film according to any one of

[17] to

[19] , wherein the thickness of the surface resin layer is 0.1 μm or more and 10 μm or less. [twenty one] The polyethylene film according to any one of [1] to

[20] , wherein the thickness of the film layer is 5 μm or more and 100 μm or less. [twenty two] The polyethylene film according to any one of [1] to

[21] , wherein the ratio of the thickness of the film layer to the total thickness of the polyethylene film is 20% or more and less than 100%. [twenty three] The polyethylene film according to any one of [1] to

[22] , wherein the arithmetic mean height Sa of the surface of the film layer, measured in accordance with ISO 25178, is less than 0.50 μm. [twenty four] The polyethylene film according to any one of [1] to

[23] , wherein the inorganic layer has an arithmetic mean height Sa of less than 0.50 μm on the surface, as measured in accordance with ISO 25178. [twenty five] The polyethylene film according to any one of [1] to

[24] , wherein the developed area ratio Sdr of the surface of the film layer, measured in accordance with ISO 25178, is less than 4.90%.

[26] The polyethylene film according to any one of [1] to

[25] , wherein the inorganic layer has a developed surface area ratio Sdr of less than 5.20% as measured in accordance with ISO 25178.

[27] The polyethylene film according to any one of [1] to

[26] , which is a packaging film.

[28] A packaging material comprising the polyethylene film according to any one of [1] to

[27] .

[29]

[28] The packaging material according to

[28] , further comprising a coating layer on at least one surface of the polyethylene film.

[30]

[28] or

[29] , and a packaging material according to and an item within the packaging material. [Effects of the Invention]

[0009] According to the present invention, a polyethylene film having improved barrier properties can be provided. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view schematically illustrating an example of the structure of a polyethylene film according to the present embodiment. [Figure 2] FIG. 1 is a cross-sectional view schematically illustrating an example of the structure of a polyethylene film according to the present embodiment. [Figure 3] FIG. 1 is a cross-sectional view schematically illustrating an example of the structure of a polyethylene film according to the present embodiment. [Figure 4] FIG. 1 is a cross-sectional view schematically illustrating an example of the structure of a polyethylene film according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the drawings are schematic diagrams and do not correspond to actual dimensional proportions. In this specification, "A to B" indicating a numerical range means A or more and B or less unless otherwise specified.

[0012] 1 and 2 are cross-sectional views schematically illustrating an example of the structure of a polyethylene film according to this embodiment. As shown in Fig. 1 and Fig. 2, a polyethylene film 100 according to this embodiment includes a film layer 101 containing an ethylene polymer (A), an inorganic layer 103 containing an inorganic material (B) on the film layer 101, and In accordance with JIS C2151:2019, the thermal shrinkage rate in the MD direction X when heated at 100°C for 15 minutes MD100 However, it is less than 5.0%.

[0013] The present inventors have found that in a polyethylene film 100 comprising a film layer 101 containing an ethylene polymer (A) and an inorganic layer 103 containing an inorganic material (B), there is a correlation between the heat shrinkage rate in the MD direction and the barrier properties. Based on this finding, the present inventors have conducted further intensive studies and found that the barrier properties of the polyethylene film can be improved by setting the heat shrinkage rate within a predetermined range, thereby completing the present invention. More specifically, they have found that the balance between the water vapor barrier property and the oxygen barrier property of the polyethylene film 100 can be improved by setting the heat shrinkage rate within a predetermined range.

[0014] According to JIS C2151:2019, the heat shrinkage rate X in the MD direction of polyethylene film 100 when heated at 100°C for 15 minutes MD100 The thermal shrinkage rate X is less than 5.0%. MD100is preferably 4.5% or less, more preferably 4.0% or less, even more preferably 3.5% or less, even more preferably 3.0% or less, even more preferably 2.5% or less, even more preferably 2.0% or less, even more preferably 1.5% or less. MD100 By setting the heat shrinkage rate X in the above range, the barrier property of the polyethylene film 100 can be further improved. MD100 By setting the temperature within the above range, the balance of thermal dimensional stability and bag formability can be improved. Heat shrinkage rate X MD100 The lower limit of is not particularly limited, but may be, for example, 0% or more, 0.01% or more, 0.1% or more, or 0.5% or more.

[0015] According to JIS C2151:2019, the heat shrinkage rate X in the TD direction of polyethylene film 100 when heated at 100°C for 15 minutes TD100 is preferably 0.0% or more and 7.5% or less, more preferably 0.1% or more and 5.0% or less, even more preferably 0.1% or more and 3.0% or less, and even more preferably 0.2% or more and 2.0% or less. TD100 By setting the heat shrinkage rate X in the above range, the barrier property of the polyethylene film 100 can be further improved. TD100 By setting the temperature within the above range, the balance of thermal dimensional stability and bag formability can be improved.

[0016] In addition, the heat shrinkage rate X MD100 [%] and X TD100 [%] is calculated using the following method. First, a 10 cm x 10 cm test piece is cut out from polyethylene film 100, and this test piece is heat-treated at 100 ° C for 15 minutes. Then, the length in the MD direction of the test piece after heat treatment is measured. 100 The length of the test piece in the TD direction after heat treatment is defined as TD [cm]. 100 When expressed in [cm], X MD100 [%] is 100 × (10-MD 100 ) / 10, and X TD100 [%] is 100×(10-TD 100) / 10.

[0017] According to JIS C2151:2019, the heat shrinkage rate X in the TD direction of polyethylene film 100 when heated at 100°C for 15 minutes TD100 and the thermal shrinkage rate in the MD direction X MD100 The absolute value of the difference between the thermal shrinkage rate X and the thermal shrinkage rate X is preferably 5.0% or less, more preferably 4.5% or less, even more preferably 4.0% or less, even more preferably 3.5% or less, even more preferably 3.0% or less, even more preferably 2.5% or less, even more preferably 2.0% or less, and even more preferably 1.5% or less. TD100 and the heat shrinkage rate X MD100 By setting the absolute value of the difference between the heat shrinkage rate X and the heat shrinkage rate X to fall within the above range, the barrier properties of the polyethylene film 100 can be further improved. TD100 and the heat shrinkage rate X MD100 By setting the absolute value of the difference between these values within the above range, the balance of thermal dimensional stability and bag formability can be improved. Heat shrinkage rate X TD100 and the heat shrinkage rate X MD100 The lower limit of the absolute value of the difference from is not particularly limited, and may be, for example, 0% or more, 0.01% or more, 0.1% or more, or 0.5% or more.

[0018] Heat shrinkage rate X MD100 to heat shrinkage rate X TD100 The value obtained by subtracting the above is preferably 0.0% or more and 5.0% or less, more preferably 0.1% or more and 4.5% or less, even more preferably 0.2% or more and 4.0% or less, even more preferably 0.5% or more and 3.5% or less, even more preferably 0.75% or more and 3.0% or less, and even more preferably 1.0% or more and 2.5% or less. MD100 to heat shrinkage rate X TD100 By setting the value obtained by subtracting X from the above range, the barrier properties of the polyethylene film 100 can be further improved. MD100 to heat shrinkage rate X TD100 By setting the value obtained by subtracting 1 from 2 in the above range, the performance balance between thermal dimensional stability and bag formability can be improved.

[0019] According to JIS C2151:2019, the heat shrinkage rate X in the MD direction of polyethylene film 100 when heated at 120°C for 15 minutes MD120 is preferably less than 26.0%, more preferably 25.0% or less, even more preferably 20.0% or less, even more preferably 15.0% or less, even more preferably 13.0% or less, and even more preferably 12.0% or less. MD120 By setting the heat shrinkage rate X in the above range, the barrier property of the polyethylene film 100 can be further improved. MD120 By setting the temperature within the above range, the balance of thermal dimensional stability and bag formability can be improved. Heat shrinkage rate X MD120 The lower limit of is not particularly limited, but may be, for example, 0% or more, 0.01% or more, 0.1% or more, or 0.5% or more.

[0020] According to JIS C2151:2019, the heat shrinkage rate X in the TD direction of polyethylene film 100 when heated at 120°C for 15 minutes TD120 is preferably 0.0% or more and 50.0% or less, more preferably 0.1% or more and 40.0% or less, even more preferably 0.2% or more and 30.0% or less, even more preferably 0.4% or more and 20.0% or less, even more preferably 0.5% or more and 15.0% or less, even more preferably 0.5% or more and 10.0% or less, even more preferably 0.5% or more and 5.0% or less, even more preferably 0.5% or more and 3.0% or less, and even more preferably 0.5% or more and 1.0% or less. TD120 By setting the heat shrinkage rate X in the above range, the barrier property of the polyethylene film 100 can be further improved. TD120 By setting the temperature within the above range, the balance of thermal dimensional stability and bag formability can be improved.

[0021] In addition, the heat shrinkage rate X MD120 [%] and X TD120 [%] is the heat shrinkage rate X of the above-mentioned polyethylene film 100 when heated at 100°C for 15 minutes. MD100 [%] and X TD100The measurement of [%] can be carried out in the same manner except that the heating temperature is 120°C.

[0022] According to JIS C2151:2019, the thermal shrinkage rate X in the TD direction when heated at 120°C for 15 minutes TD120 and the heat shrinkage rate X in the MD direction when heated at 120°C for 15 minutes in accordance with JIS C2151:2019. MD120 The absolute value of the difference between the thermal shrinkage rate X and the thermal shrinkage rate X is preferably 28.0% or less, more preferably 25.0% or less, even more preferably 20.0% or less, even more preferably 15.0% or less, and even more preferably 12.0% or less. TD120 and the heat shrinkage rate X MD120 By setting the absolute value of the difference between the heat shrinkage rate X and the heat shrinkage rate X to fall within the above range, the barrier properties of the polyethylene film 100 can be further improved. TD120 and the heat shrinkage rate X MD120 By setting the absolute value of the difference between these values within the above range, the balance of thermal dimensional stability and bag formability can be improved. Heat shrinkage rate X TD120 and the heat shrinkage rate X MD120 The lower limit of the absolute value of the difference from is not particularly limited, and may be, for example, 0% or more, 0.01% or more, 0.1% or more, or 0.5% or more.

[0023] According to JIS C2151:2019, the heat shrinkage rate X in the MD direction when heated at 120°C for 15 minutes MD120 According to JIS C2151:2019, the thermal shrinkage rate X in the TD direction when heated at 120°C for 15 minutes TD120 The value obtained by subtracting the above is preferably 0.0% or more and 28.0% or less, more preferably 0.5% or more and 27.5% or less, even more preferably 1.0% or more and 25.0% or less, even more preferably 2.0% or more and 22.5% or less, and even more preferably 5.0% or more and 20.0% or less. MD120 to heat shrinkage rate X TD120 By setting the value obtained by subtracting X from the above range, the barrier properties of the polyethylene film 100 can be further improved. MD120 to heat shrinkage rate X TD120By setting the value obtained by subtracting 1 from 2 in the above range, the performance balance between thermal dimensional stability and bag formability can be improved.

[0024] The density of the polyethylene film 100, measured in accordance with JIS K 7112:1999, is preferably 0.910 g / cm 3 More than 0.970g / cm 3 or less, more preferably 0.915 g / cm 3 More than 0.965g / cm 3 or less, more preferably 0.920 g / cm 3 More than 0.960g / cm 3 or less, more preferably 0.925 g / cm 3 More than 0.955g / cm 3 or less, more preferably 0.930 g / cm 3 More than 0.950g / cm 3 or less, more preferably 0.935 g / cm 3 More than 0.945g / cm 3 By setting the density of the polyethylene film 100 to the above lower limit or more, it is possible to achieve a better balance among various performances such as thermal dimensional stability, film-forming ability, heat resistance, mechanical properties, and rigidity. Furthermore, by setting the density of the polyethylene film 100 to the above upper limit or less, it is possible to improve the film-forming ability.

[0025] The melt mass flow rate (MFR) of the polyethylene film 100, measured in accordance with JIS K 7210:1999 at 190°C under a load of 2160 g, is preferably 0.1 g / 10 min to 5.0 g / 10 min, more preferably 0.1 g / 10 min to 4.5 g / 10 min, even more preferably 0.2 g / 10 min to 4.0 g / 10 min, even more preferably 0.2 g / 10 min to 3.5 g / 10 min, even more preferably 0.3 g / 10 min to 3.0 g / 10 min, even more preferably 0.5 g / 10 min to 2.5 g / 10 min, and even more preferably 0.8 g / 10 min to 2.0 g / 10 min. By adjusting the melt mass flow rate (MFR) of the polyethylene film 100 to be equal to or greater than the lower limit, the balance of fluidity, film formability, and thermal dimensional stability can be improved. Furthermore, by setting the melt mass flow rate (MFR) of the polyethylene film 100 to the above upper limit or less, the stiffness of the polyethylene film 100 can be improved while improving the balance of film-forming properties and thermal dimensional stability.

[0026] The thickness of the polyethylene film 100 is preferably 5 μm to 100 μm, more preferably 5 μm to 50 μm, even more preferably 10 μm to 40 μm, even more preferably 12 μm to 30 μm, and even more preferably 15 μm to 30 μm. By setting the thickness of the polyethylene film 100 within the above range, it is possible to further improve the balance of performance such as thermal dimensional stability, film-forming properties, water vapor barrier properties, cost, mechanical properties, transparency, bag-forming properties, handleability, appearance, and light weight.

[0027] The total value (T1+T2) of the tensile modulus of elasticity in the MD direction T1 and the tensile modulus of elasticity in the TD direction T2 of the polyethylene film 100 measured in accordance with JIS K7127:1999 using a tensile tester under conditions of a measurement temperature of 23±2°C, 50±5% RH, and a tensile speed of 5 mm / min is preferably 500 MPa or more and 9000 MPa or less, more preferably 750 MPa or more and 8000 MPa or less, even more preferably 1000 MPa or more and 7000 MPa or less, and still more preferably 1250 MPa or more and 6000 MPa or less. When the sum (T1+T2) of the tensile modulus of elasticity T1 in the MD direction and the tensile modulus of elasticity T2 in the TD direction of the polyethylene film 100 is equal to or greater than the above-mentioned lower limit, the performance balance of the polyethylene film 100, such as thermal dimensional stability, film-forming properties, water vapor barrier properties, mechanical properties, transparency, bag-forming properties, and handleability, can be improved, and the stiffness of the polyethylene film 100 can be improved. Furthermore, when the sum (T1+T2) of the tensile modulus of elasticity T1 in the MD direction and the tensile modulus of elasticity T2 in the TD direction of the polyethylene film 100 is equal to or less than the above upper limit, problems such as breakage during film formation of the polyethylene film 100 are less likely to occur, thereby improving industrial continuous productivity. Such a tensile modulus is a substitute value for quantitatively measuring the stiffness of the film, and can be adjusted, for example, by adjusting the type and content ratio of the ethylene polymer (A) contained in the film layer 101, the thickness and stretching ratio of the film layer 101, the constituent material and thickness of the surface resin layer 103, etc.

[0028] The tensile modulus T1 in the MD direction of the polyethylene film 100 is preferably 200 MPa or more and 4000 MPa or less, more preferably 300 MPa or more and 3000 MPa or less, even more preferably 350 MPa or more and 2500 MPa or less, and still more preferably 400 MPa or more and 2300 MPa or less. When the tensile modulus T1 in the MD direction of the polyethylene film 100 is equal to or greater than the above lower limit, the performance balance of the polyethylene film 100 can be improved, including thermal dimensional stability, film-forming properties, water vapor barrier properties, mechanical properties, transparency, bag-forming properties, handleability, and packaging suitability. When the tensile modulus T1 in the MD of the polyethylene film 100 is equal to or less than the upper limit, the polyethylene film 100 can have an improved balance of thermal dimensional stability, antistatic properties, bag-forming properties, and packaging suitability.

[0029] The tensile modulus T2 of the polyethylene film 100 in the TD direction is preferably 200 MPa or more and 5000 MPa or less, more preferably 300 MPa or more and 4500 MPa or less, even more preferably 400 MPa or more and 4000 MPa or less, even more preferably 450 MPa or more and 3500 MPa or less, and even more preferably 500 MPa or more and 3000 MPa or less. When the tensile modulus T2 in the TD direction of the polyethylene film 100 is equal to or greater than the above lower limit, the performance balance of the polyethylene film 100 can be improved, including thermal dimensional stability, film-forming properties, water vapor barrier properties, mechanical properties, transparency, bag-forming properties, handleability, and packaging suitability. When the tensile modulus T2 in the TD of the polyethylene film 100 is equal to or less than the upper limit, the polyethylene film 100 can have an improved balance of thermal dimensional stability, antistatic properties, bag-forming properties, and packaging suitability.

[0030] The moisture permeability (water vapor permeability) measured by the following method is preferably 3.2 g / (m 2 ·day) or less, more preferably 2.6g / (m 2 ·day) or less, more preferably 2.0 g / (m 2 ·day) or less, more preferably 1.6g / (m 2 ·day) or less, more preferably 1.2 g / (m 2 ·day) or less, more preferably 0.8g / (m 2 ·day) or less, more preferably 0.4g / (m 2 ·day) or less, more preferably 0.3g / (m 2 By setting the moisture permeability of the polyethylene film 100 within the above range, the water vapor barrier property can be further improved. The lower the moisture permeability of the polyethylene film 100, the better. Therefore, the lower limit is not particularly limited. For example, 2 ·day) or more, and 0.01g / (m 2 ·day) or more, and 2 ·day) or more. (Measurement method) An adhesive is applied to one side of a 50 μm thick LLDPE film. The polyethylene film and the LLDPE film are then laminated together so that the inorganic layer side of the polyethylene film is in contact with the adhesive-coated side of the LLDPE film, yielding a multilayer film. The resulting multilayer film is then folded back so that the LLDPE film faces inward, and the two sides are heat-sealed to form a bag. Calcium chloride is then placed inside the resulting bag. The other side of the bag is then heat-sealed to reduce the surface area to 0.01 m. 2 The resulting bag is then stored at 40°C and 90% RH for 300 hours. The weight of the calcium chloride is measured before and after storage, and the moisture permeability is calculated from the difference.

[0031] The oxygen permeability measured by the following method is preferably 800 mL / (m 2 ·day·MPa) or less, more preferably 600mL / (m 2 ·day·MPa) or less, more preferably 400mL / (m 2 ·day·MPa) or less, more preferably 200mL / (m 2 ·day·MPa) or less, more preferably 100mL / (m 2 ·day·MPa) or less, more preferably 70mL / (m 2 ·day·MPa) or less, more preferably 50mL / (m 2 ·day·MPa) or less, more preferably 40mL / (m 2 By setting the oxygen permeability of the polyethylene film 100 within the above range, the oxygen barrier properties can be further improved. The lower the oxygen permeability of the polyethylene film 100, the better. Therefore, the lower limit is not particularly limited. For example, 2 ·day·MPa) or more, and 0.1mL / (m 2 ·day·MPa) or more, and 1mL / (m 2 ·day·MPa) or more, and 5mL / (m 2 ·day·MPa) or more. (Measurement method) An adhesive is applied to one side of a 50 μm thick LLDPE film. Next, the polyethylene film and the LLDPE film are laminated together so that the inorganic layer side of the polyethylene film is in contact with the adhesive-coated side of the LLDPE film, thereby obtaining a multilayer film. The oxygen permeability (mL / (m 2 ·day·MPa)) is measured in accordance with JIS K7126:2006 under conditions of 20°C and 90% RH.

[0032] Each layer constituting the polyethylene film 100 will be described below.

[0033] [Film layer] The film layer 101 contains an ethylene polymer (A).

[0034] The ethylene polymer (A) preferably contains polyethylene. The polyethylene contained in the ethylene polymer (A) preferably contains one or more types selected from the group consisting of low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), and high-density polyethylene (HDPE). The polyethylene contained in the ethylene polymer (A) more preferably contains one or more types selected from the group consisting of low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and high-density polyethylene (HDPE), and even more preferably contains one or more types selected from the group consisting of linear low-density polyethylene (LLDPE) and high-density polyethylene (HDPE). This allows for a good balance of various properties such as thermal dimensional stability, film-forming ability, heat resistance, water vapor barrier property, mechanical properties, and rigidity. Here, low-density polyethylene (LDPE) is 0.910 g / cm 3 More than 0.930g / cm 3 Medium density polyethylene (MDPE) refers to polyethylene having a density less than 0.930 g / cm 3 More than 0.942g / cm 3High density polyethylene (HDPE) refers to polyethylene having a density less than 0.942 g / cm 3 It refers to polyethylene with a density of 100% or more. Low-density polyethylene with little branching is called linear low-density polyethylene (LLDPE).

[0035] The content of the ethylene polymer (A) in the film layer 101 is preferably 75% by mass or more and 100% by mass or less, more preferably 80% by mass or more and 100% by mass or less, and even more preferably 85% by mass or more and 100% by mass or less, when the entire film layer 101 is taken as 100% by mass. By setting the content of the ethylene polymer (A) in the film layer 101 to the above-mentioned lower limit or more, it is possible to achieve a good balance of various performance properties such as thermal dimensional stability, film-forming ability, heat resistance, mechanical properties, and rigidity. Furthermore, by setting the content of the ethylene polymer (A) in the film layer 101 to the above-mentioned upper limit or less, it is possible to improve the balance of performance properties such as processability and continuous productivity.

[0036] The density of the ethylene polymer (A), measured in accordance with JIS K 7112:1999, is preferably 0.910 g / cm 3 More than 0.970g / cm 3 or less, more preferably 0.915 g / cm 3 More than 0.965g / cm 3 or less, more preferably 0.920 g / cm 3 More than 0.960g / cm 3 or less, more preferably 0.925 g / cm 3 More than 0.955g / cm 3 or less, more preferably 0.930 g / cm 3 More than 0.950g / cm 3 or less, more preferably 0.935 g / cm 3 More than 0.945g / cm 3 By adjusting the density of the ethylene polymer (A) to the above lower limit or more, it is possible to achieve a good balance among various properties such as thermal dimensional stability, film-forming ability, heat resistance, mechanical properties, rigidity, etc. Furthermore, by adjusting the density of the ethylene polymer (A) to the above upper limit or less, it is possible to improve the film-forming ability. When two or more types of polymers are used as the ethylene polymer (A), the density of a mixture obtained by melt blending two or more types of ethylene polymers by a known method can be used.

[0037] The melt mass flow rate (MFR) of the ethylene polymer (A), measured in accordance with JIS K 7210:1999 under conditions of 190°C and a load of 2160 g, is preferably 0.1 g / 10 min to 5.0 g / 10 min, more preferably 0.2 g / 10 min to 4.5 g / 10 min, even more preferably 0.4 g / 10 min to 4.0 g / 10 min, even more preferably 0.6 g / 10 min to 3.5 g / 10 min, and even more preferably 0.8 g / 10 min to 3.0 g / 10 min. By adjusting the melt mass flow rate (MFR) of the ethylene polymer (A) to be equal to or greater than the above lower limit, the balance of performance among fluidity, film-forming ability, and thermal dimensional stability can be improved. Furthermore, by setting the melt mass flow rate (MFR) of the ethylene polymer (A) to the above upper limit or less, the stiffness of the polyethylene film 100 can be improved while improving the balance of film-forming properties and thermal dimensional stability. When two or more types of polymers are used as the ethylene polymer (A), the MFR of a mixture obtained by melt blending two or more types of polymers by a known method can be used.

[0038] The melting point of the ethylene polymer (A) measured by differential scanning calorimetry (DSC) is preferably 90° C. or higher and 150° C. or lower, more preferably 100° C. or higher and 150° C. or lower, even more preferably 110° C. or higher and 140° C. or lower, even more preferably 120° C. or higher and 140° C. or lower, and still more preferably 125° C. or higher and 135° C. By adjusting the melting point of the ethylene polymer (A) to fall within the above range, the balance of properties such as film-forming ability, thermal dimensional stability, heat resistance, water vapor barrier property, mechanical properties, rigidity, bag-forming ability, and flowability can be improved. When two or more types of polymers are used as the ethylene polymer (A), the melting point of the ethylene polymer (A) is the peak temperature of the maximum melting peak.

[0039] The ethylene polymer (A) may contain an ethylene-α-olefin copolymer, which may be a random copolymer or a block copolymer. The ethylene-α-olefin copolymer preferably contains an ethylene-α-olefin random copolymer, more preferably contains one or more copolymers selected from the group consisting of an ethylene-1-butene random copolymer and an ethylene-propylene random copolymer, and even more preferably contains an ethylene-1-butene random copolymer, which can improve the balance of thermal dimensional stability, film-forming ability, and flexibility.

[0040] The film layer 101 is composed of, for example, an ethylene-based resin composition containing an ethylene-based polymer (A). The ethylene-based resin composition may contain one or more resins selected from the group consisting of homopolymers or copolymers of α-olefins other than ethylene, such as propylene, 1-butene, hexene-1, 4-methyl-pentene-1, and 1-octene; homopolypropylene; random copolymers of propylene and α-olefins having from 2 to 10 carbon atoms; and ionomer resins.

[0041] (Other ingredients) The film layer 101 may contain various additives, such as tackifiers, heat stabilizers, weather stabilizers, antioxidants, ultraviolet absorbers, lubricants, slip agents, nucleating agents, antiblocking agents, antistatic agents, antifogging agents, pigments, dyes, and inorganic or organic fillers, as needed, within the scope of the present embodiment.

[0042] (Film layer manufacturing method) The film layer 101 can be produced, for example, by mixing or melt-kneading the components using a dry blend, a tumbler mixer, a Banbury mixer, a single-screw extruder, a twin-screw extruder, a high-speed twin-screw extruder, a heat roll, or the like.

[0043] The film layer 101 may be a single layer or may be a multi-layer structure.

[0044] The film layer 101 preferably includes a stretched film layer, more preferably a uniaxially stretched film layer or a biaxially stretched film layer, which allows the polyethylene film 100 to have a good balance of various properties such as thermal dimensional stability, film-forming properties, heat resistance, barrier properties, mechanical properties, and rigidity.

[0045] The thickness of the film layer 101 is preferably 5 μm to 100 μm, more preferably 5 μm to 50 μm, even more preferably 10 μm to 40 μm, even more preferably 12 μm to 30 μm, and even more preferably 15 μm to 25 μm. By setting the thickness of the film layer 101 within the above range, it is possible to improve the balance of performance such as thermal dimensional stability, film-forming properties, water vapor barrier properties, cost, mechanical properties, transparency, bag-forming properties, handleability, appearance, and lightness.

[0046] In the polyethylene film 100, the ratio of the thickness of the film layer 101 to the overall thickness of the polyethylene film 100 is preferably 20% or more and less than 100%, more preferably 25% or more and less than 100%, even more preferably 30% or more and less than 100%, even more preferably 35% or more and less than 100%, even more preferably 50% or more and less than 100%, even more preferably 60% or more and 99% or less, even more preferably 70% or more and 95% or less, and even more preferably 75% or more and 90% or less. By setting the ratio of the thickness of the film layer 101 to the overall thickness of the polyethylene film 100 within the above range, it is possible to improve the balance of performance such as thermal dimensional stability, film-forming ability, water vapor barrier property, cost, mechanical properties, transparency, bag-forming ability, handleability, appearance, and light weight.

[0047] The arithmetic mean height Sa of the surface of the film layer 101 or the surface resin layer 105 described below, measured in accordance with ISO 25178, is preferably less than 0.50 μm, more preferably 0.30 μm or less, even more preferably 0.20 μm or less, even more preferably 0.15 μm or less, and even more preferably 0.10 μm or less. By setting the arithmetic mean height Sa of the surface of the film layer 101 or the surface resin layer 105 described below within the above range, good bonding can be achieved between the film layer 101 or the surface resin layer 105 described below and another layer (e.g., the inorganic layer 103) provided on the surface of the film layer 101 or the surface resin layer 105 described below, and the barrier properties of the polyethylene film 100 can be further improved. The lower limit of the arithmetic mean height Sa on the surface of the film layer 101 or the surface resin layer 105 described below is not particularly limited, but may be, for example, 0.001 μm or more, 0.005 μm or more, 0.01 μm or more, or 0.03 μm or more.

[0048] The developed area ratio Sdr on the surface of the film layer 101 or the surface resin layer 105 described below, measured in accordance with ISO 25178, is preferably less than 4.90%, more preferably less than 4.50%, even more preferably less than 3.50%, even more preferably less than 2.50%, even more preferably less than 1.50%, and even more preferably less than 1.00%. By setting the developed area ratio Sdr on the surface of the film layer 101 or the surface resin layer 105 described below within the above range, good bonding can be achieved between the film layer 101 or the surface resin layer 105 described below and another layer (e.g., the inorganic layer 103) provided on the surface of the film layer 101 or the surface resin layer 105 described below, and the barrier properties of the polyethylene film 100 can be further improved. The lower limit of the developed area ratio Sdr on the surface of the film layer 101 or the surface resin layer 105 described below is not particularly limited, but may be, for example, 0.01% or more, 0.05% or more, 0.10% or more, or 0.50% or more.

[0049] [Inorganic layer] The inorganic layer 103 is provided on the film layer 101 and contains an inorganic material (B).

[0050] The inorganic material (B) includes, for example, one or more metals and metal oxides capable of forming a thin film having barrier properties. More specifically, the inorganic material (B) includes one or more elements selected from the group consisting of elements from Group 2A of the periodic table, such as beryllium, magnesium, calcium, strontium, and barium; elements from the periodic table, such as titanium, zirconium, ruthenium, hafnium, and tantalum; elements from Group 2B of the periodic table, such as zinc; elements from Group 3A of the periodic table, such as aluminum, gallium, indium, and thallium; elements from Group 4A of the periodic table, such as silicon, germanium, and tin; and elements from Group 6A of the periodic table, such as selenium and tellurium (the names of the groups in the periodic table are shown in the old CAS format).

[0051] The inorganic material (B) preferably contains one or more inorganic substances selected from the group consisting of silicon oxide, silicon oxynitride, silicon nitride, aluminum oxide, and aluminum, because it provides an excellent balance between barrier properties, cost, etc. The silicon oxide may contain silicon dioxide, silicon monoxide, or silicon suboxide. In particular, the inorganic material (B) more preferably contains aluminum, because it provides an excellent balance between barrier properties, cost, etc.

[0052] The inorganic layer 103 may be a single layer or may have a structure in which multiple layers are laminated. When the inorganic layer 103 has a structure in which multiple layers are laminated, the layers may be the same type of inorganic layer or different types of inorganic layers.

[0053] The thickness of the inorganic layer 103 is preferably more than 0 nm and not more than 500 nm, more preferably 5 nm to 200 nm, even more preferably 10 nm to 100 nm, even more preferably 20 nm to 80 nm, and even more preferably 30 nm to 60 nm. By setting the thickness of the inorganic layer 103 within the above range, it is possible to improve the balance of performance such as thermal dimensional stability, film-forming properties, water vapor barrier properties, cost, mechanical properties, transparency, bag-forming properties, handleability, appearance, and lightness.

[0054] The arithmetic mean height Sa of the surface of the inorganic layer 103, measured in accordance with ISO 25178, is preferably less than 0.50 μm, more preferably 0.30 μm or less, even more preferably 0.20 μm or less, even more preferably 0.15 μm or less, even more preferably 0.12 μm or less, and even more preferably 0.10 μm or less. By setting the arithmetic mean height Sa of the surface of the inorganic layer 103 within the above range, good bonding can be achieved between the inorganic layer 103 and another layer (e.g., film layer 101) provided on the surface of the inorganic layer 103, and the barrier properties of the polyethylene film 100 can be further improved. The lower limit of the arithmetic mean height Sa on the surface of the inorganic layer 103 is not particularly limited, but may be, for example, 0.001 μm or more, 0.005 μm or more, 0.01 μm or more, or 0.03 μm or more.

[0055] The developed area ratio Sdr on the surface of the inorganic layer 103, measured in accordance with ISO 25178, is preferably less than 5.20%, more preferably less than 4.00%, even more preferably less than 3.50%, even more preferably less than 3.00%, even more preferably less than 2.50%, and even more preferably less than 2.00%. By setting the developed area ratio Sdr on the surface of the inorganic layer 103 within the above range, good bonding can be achieved between the inorganic layer 103 and another layer (e.g., the film layer 101) provided on the surface of the inorganic layer 103, and the barrier properties of the polyethylene film 100 can be further improved. The lower limit of the developed area ratio Sdr on the surface of the inorganic layer 103 is not particularly limited, but may be, for example, 0.01% or more, 0.05% or more, 0.10% or more, or 0.50% or more.

[0056] The method for forming the inorganic layer 103 is not particularly limited, and the inorganic layer 103 can be formed on one or both sides of the film layer 101 by, for example, a vacuum process such as vacuum deposition, sputtering, or plasma vapor deposition (CVD), or a sol-gel process.

[0057] [Surface resin layer] 3 and 4 are cross-sectional views schematically illustrating an example of the structure of a polyethylene film according to this embodiment. As shown in FIGS. 3 and 4, the polyethylene film 100 preferably further comprises a surface resin layer 105 on at least one surface of the film layer 101. More specifically, the polyethylene film 100 preferably further comprises a surface resin layer 105 on at least one surface of the film layer 101, the surface resin layer 105 being made of a polyolefin resin composition different from the polyolefin resin composition constituting the film layer 101. This provides the polyethylene film 100 with properties such as heat fusion resistance, heat sealability, antistatic properties, blocking resistance, printability, and slip properties. The surface resin layer 105 may be provided between the film layer 101 and the inorganic layer 103. The surface resin layer 105 may be provided on both sides of the film layer 101. By providing the surface resin layer 105 on both sides of the film layer 101, it is possible to impart a function to each surface of the film layer 101. When the surface resin layer 105 is provided on both sides of the film layer 101, the surface resin layer 105 provided on one side preferably has heat-sealing properties. The polyethylene film 100 can be folded with this side facing inward and the edges heat-sealed to form a bag. In this case, the surface resin layer 105 provided on the other side preferably has blocking resistance, antistatic properties, printability, etc.

[0058] The surface resin layer 105 is preferably provided as the outermost layer of the polyethylene film 100. This can improve the functions of the polyethylene film 100, such as heat fusion resistance, heat sealing properties, antistatic properties, blocking resistance, printability, and slip properties.

[0059] The surface resin layer 105 is preferably provided so as to be in direct contact with the surface of the film layer 101. This simplifies the manufacturing process of the polyethylene film 100.

[0060] The surface resin layer 105 is made of, for example, a polyolefin-based resin composition containing polyolefin. The polyolefin-based resin composition may contain one or more materials selected from the group consisting of homopolymers or copolymers of α-olefins such as ethylene, propylene, 1-butene, hexene-1, 4-methyl-pentene-1, and 1-octene; high-pressure low-density polyethylene; linear low-density polyethylene (LLDPE); high-density polyethylene; homopolypropylene; random copolymers of propylene and α-olefins having from 2 to 10 carbon atoms; ethylene-vinyl acetate copolymers (EVA); and ionomer resins.

[0061] The surface resin layer 105 preferably contains an ethylene-based polymer (C). This improves the balance of various properties, such as thermal dimensional stability, film-forming properties, heat resistance, water vapor barrier properties, mechanical properties, and rigidity. The polyethylene contained in the ethylene-based polymer (C) preferably contains one or more polyethylenes selected from the group consisting of low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), and high-density polyethylene (HDPE), more preferably one or more polyethylenes selected from the group consisting of low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and high-density polyethylene (HDPE), and even more preferably one or more polyethylenes selected from the group consisting of linear low-density polyethylene (LLDPE) and high-density polyethylene (HDPE). This improves the balance of various properties, such as thermal dimensional stability, film-forming properties, heat resistance, water vapor barrier properties, mechanical properties, and rigidity.

[0062] The surface resin layer 105 may contain the ethylene polymer (A) contained in the film layer 101. That is, the film layer 101 and the surface resin layer 105 may contain the same ethylene polymer. For example, the film layer 101 and the surface resin layer 105 may both contain linear low-density polyethylene (LLDPE). Furthermore, the polyolefin resin composition constituting the surface resin layer 105 may be the same as the polyolefin resin composition constituting the film layer 101.

[0063] Furthermore, when the surface resin layer 105 is provided on both sides of the polyethylene film 100, the polyolefin resin compositions constituting the respective surface resin layers 105 may be the same or different.

[0064] The content of the ethylene polymer (C) in the surface resin layer 105 is preferably 75% by mass or more and 100% by mass or less, more preferably 80% by mass or more and 100% by mass or less, and even more preferably 85% by mass or more and 100% by mass or less, when the entire surface resin layer 105 is taken as 100% by mass. By setting the content of the ethylene polymer (C) in the surface resin layer 105 to be equal to or greater than the above-mentioned lower limit, it is possible to achieve a good balance between various performance properties such as thermal dimensional stability, film-forming ability, heat resistance, mechanical properties, and rigidity. Furthermore, by setting the content of the ethylene polymer (C) in the surface resin layer 105 to be equal to or less than the above-mentioned upper limit, it is possible to improve the balance of performance properties such as processability and continuous productivity.

[0065] The ethylene polymer (C) may contain an ethylene-α-olefin copolymer. The ethylene-α-olefin copolymer may be a random copolymer or a block copolymer. From the viewpoint of improving the balance of thermal dimensional stability, film-forming ability, and flexibility, the ethylene-α-olefin copolymer preferably contains an ethylene-α-olefin random copolymer, more preferably contains one or more copolymers selected from the group consisting of an ethylene-1-butene random copolymer and an ethylene-propylene random copolymer, and even more preferably contains an ethylene-1-butene random copolymer.

[0066] (Other ingredients) The surface resin layer 105 may contain various additives such as tackifiers, heat stabilizers, weather stabilizers, antioxidants, ultraviolet absorbers, lubricants, slip agents, nucleating agents, antiblocking agents, antistatic agents, antifogging agents, pigments, dyes, inorganic or organic fillers, etc., as needed, within the scope that does not impair the purpose of this embodiment.

[0067] (Method of manufacturing surface resin layer) The surface resin layer 105 can be produced, for example, by mixing or melt-kneading the components using a dry blend, tumbler mixer, Banbury mixer, single-screw extruder, twin-screw extruder, high-speed twin-screw extruder, heat roll, or the like.

[0068] The surface resin layer 105 may be a single layer or may be a multi-layer structure.

[0069] The surface resin layer 105 preferably includes a stretched film layer, more preferably a uniaxially stretched film layer or a biaxially stretched film layer, which allows the polyethylene film 100 to have a good balance of various properties such as thermal dimensional stability, film-forming properties, heat resistance, barrier properties, mechanical properties, and rigidity.

[0070] The thickness of the surface resin layer 105 is preferably 0.1 μm to 10 μm, more preferably 0.5 μm to 10 μm, even more preferably 1 μm to 7.5 μm, and even more preferably 2 μm to 5 μm. By setting the thickness of the surface resin layer 105 within the above range, it is possible to improve the balance of performance such as thermal dimensional stability, film-forming properties, water vapor barrier properties, cost, mechanical properties, transparency, bag-forming properties, handleability, appearance, and lightness.

[0071] In the polyethylene film 100, the ratio of the thickness of the surface resin layer 105 to the total thickness of the polyethylene film 100 is preferably more than 0% and not more than 50%, more preferably 1% to 40%, even more preferably 5% to 30%, and even more preferably 10% to 25%. By setting the ratio of the thickness of the surface resin layer 105 to the total thickness of the polyethylene film 100 within the above range, it is possible to improve the balance of performance such as thermal dimensional stability, film-forming properties, water vapor barrier properties, cost, mechanical properties, transparency, bag-forming properties, handleability, appearance, and light weight.

[0072] When the surface resin layer 105 is provided on both sides of the polyethylene film 100, the "thickness of the surface resin layer 105" refers to the thickness of each surface resin layer 105.

[0073] Furthermore, in the polyethylene film 100, the ratio of the "total thickness of the film layer 101 and the surface resin layer 105" to the "total thickness of the polyethylene film 100" is preferably 50% or more and less than 100%, more preferably 60% or more and less than 100%, even more preferably 70% or more and less than 100%, even more preferably 80% or more and less than 100%, even more preferably 90% or more and less than 100%, even more preferably 95% or more and less than 100%, and even more preferably 98% or more and less than 100%. By setting the ratio of the "total thickness of the film layer 101 and the surface resin layer 105" to the "total thickness of the polyethylene film 100" within the above range, it is possible to improve the balance of performance such as thermal dimensional stability, film-forming ability, water vapor barrier property, cost, mechanical properties, transparency, bag-forming ability, handleability, appearance, and light weight. In addition, when the surface resin layer 105 is provided on both sides of the polyethylene film 100, the "total thickness of the film layer 101 and the surface resin layer 105" refers to the total thickness of the film layer 101 and the thickness of each surface resin layer 105.

[0074] <Polyethylene film manufacturing method> The polyethylene film 100 can be obtained, for example, by the following procedure. First, the ethylene-based resin composition for forming the film layer 101 is co-extruded into a film, and the resulting film is biaxially stretched using a known biaxially stretched film production method such as simultaneous biaxial stretching, sequential biaxial stretching, or inflation biaxial stretching. The molding apparatus and molding conditions are not particularly limited, and conventionally known molding apparatus and molding conditions can be used. Examples of molding apparatus that can be used include a T-die extruder, a multilayer T-die extruder, an inflation molding machine, and a multilayer inflation molding machine. For biaxial stretching conditions, for example, known polyethylene film production conditions can be used. For example, in the sequential biaxial stretching method, the MD stretching temperature is preferably in the range of 100°C to 145°C, more preferably 110°C to 140°C, and even more preferably 120°C to 135°C, and the TD stretching temperature is preferably in the range of 110°C to 190°C, more preferably 120°C to 170°C. Furthermore, the MD stretch ratio is preferably in the range of 4.5 to 7 times, and the TD stretch ratio is preferably in the range of 9 to 11 times. Specifically, the stretching temperature must be set at three stages: preheating temperature (temperature at which the raw film is heated before stretching), stretching temperature (temperature during stretching), and heat setting temperature (temperature during heat setting (annealing) after stretching). The temperatures can be within the above ranges from preheating to heat setting. That is, the temperatures can be set to approximately the same as those for stretching and heat setting from the preheating stage onwards. The polyethylene film 100 of this embodiment contains an ethylene polymer (A), and therefore can be processed at higher temperatures, which can further improve the heat resistance of the resulting polyethylene film 100 and, in turn, further improve the thermal dimensional stability. When the polyethylene film 100 has a surface resin layer 105, the surface resin layer 105 can be formed in the same manner as the above-mentioned method for forming the film layer 101. The surface resin layer 105 may be formed simultaneously with the film layer 101. Alternatively, the surface resin layer 105 may be formed separately from the film layer 101, and then these may be laminated and heat-formed. Next, an inorganic layer 103 is formed on one or both sides of the obtained film layer 101 (or a laminate of the film layer 101 and the surface resin layer 105). The method for forming the inorganic layer 103 is not particularly limited, and it can be formed by, for example, a vacuum process such as a vacuum deposition method, a sputtering method, or a plasma vapor deposition method (CVD method), or a sol-gel process.

[0075] <Polyethylene film applications / packaging materials / packaging bodies> Specifically, the polyethylene film 100 of this embodiment can be suitably used as a packaging film. The polyethylene film 100 of this embodiment can be suitably used as a packaging material. That is, the packaging material of this embodiment includes the polyethylene film 100. When used as a packaging material, the polyethylene film 100 of this embodiment may be used alone, or other layers may be laminated on at least one surface of the polyethylene film 100 to form the packaging material. The other layers preferably further include one or more selected from the group consisting of an inorganic layer, a substrate layer, a coating layer, an adhesive layer, and a heat-sealing layer, more preferably one or more selected from the group consisting of an inorganic layer and a coating layer, and even more preferably a coating layer. From the viewpoint of ease of recycling, when these layers are laminated, they are preferably formed from a polyethylene-based resin. Furthermore, the packaging material of this embodiment can be suitably used for a package. The package is used, for example, for packaging an item, and specifically includes the packaging material of this embodiment and an item inside the packaging material. In particular, the packaging of this embodiment can be suitably used as a food package, and is used for packaging food, and specifically includes the packaging material of this embodiment and food inside the packaging material. There are no limitations on the foods that can be packaged in the food packaging, but examples include baked goods, rice crackers, snacks, sprinkles, grain powders, and the like. Depending on the application, only a portion of the package may be made of the packaging material of this embodiment, or substantially the entire package may be made of the packaging material of this embodiment.

[0076] From the viewpoint of improving heat sealing properties, the packaging material of the present embodiment preferably further comprises a heat-sealable layer on at least one outermost surface. The heat-sealable layer may be one or more layers selected from the group consisting of a homopolymer or copolymer of an α-olefin such as ethylene, propylene, butene-1, hexene-1, 4-methyl-pentene-1, or octene-1, a layer formed from a resin composition containing one or more polyolefins selected from the group consisting of low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), polypropylene, a polypropylene random copolymer, a low-crystalline or amorphous ethylene-propylene random copolymer, an ethylene-butene-1 random copolymer, and a propylene-butene-1 random copolymer, a layer formed from a resin composition containing ethylene-vinyl acetate copolymer (EVA), and a layer formed from a resin composition containing EVA and a polyolefin. Among these, the heat-sealable layer preferably includes a layer formed from a resin composition containing polyolefin, and more preferably includes a layer formed from a resin composition containing one or more polyethylenes selected from the group consisting of low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), and high-density polyethylene (HDPE). This makes the packaging material composed of almost a single material (monomaterial), reducing the work of separating the materials that make up the packaging material and improving the recyclability of the packaging material. The thickness of the heat-sealing layer is, for example, 10 μm or more and 300 μm or less, preferably 30 μm or more and 200 μm or less, and more preferably 50 μm or more and 150 μm or less.

[0077] From the viewpoint of improving recyclability, the content of the ethylene polymer in the packaging material of the present embodiment is preferably 50% by mass or more and less than 100% by mass, more preferably 70% by mass or more and less than 100% by mass, even more preferably 80% by mass or more and 99.9% by mass or less, even more preferably 90% by mass or more and 99.9% by mass or less, even more preferably 95% by mass or more and 99.5% by mass or less, and even more preferably 99.0% by mass or more and 99.5% by mass or less, when the entire packaging material is taken as 100% by mass. Furthermore, from the viewpoint of ease of recycling, the content of polyethylene in the packaging material of the present embodiment, when the entire packaging material is taken as 100% by mass, is preferably 50% by mass or more and less than 100% by mass, more preferably 70% by mass or more and less than 100% by mass, even more preferably 80% by mass or more and 99.9% by mass or less, even more preferably 90% by mass or more and 99.9% by mass or less, even more preferably 95% by mass or more and 99.8% by mass or less, and even more preferably 99.0% by mass or more and 99.8% by mass or less. This means that the packaging material is made up of almost a single material (monomaterial), which reduces the work required to separate the materials that make up the packaging material and improves the recyclability of the packaging material.

[0078] There is no particular limitation on the method for producing a package from the polyethylene film 100 or packaging material, and any method known in the field of packaging materials / packages, such as heat sealing or fusing, can be used as appropriate.

[0079] The polyethylene film 100 according to this embodiment is preferably used for packaging that requires good barrier properties. The packaging may be in the form of, for example, a two-sided bag or a standing pouch (pouch packaging).

[0080] Furthermore, when a package (such as a food packaging bag) is made using the polyethylene film 100 of this embodiment or a packaging material, it is preferable that the corona-treated surface is the inner surface and the non-corona-treated surface is the outer surface. Furthermore, as described above, when another layer is laminated on the polyethylene film 100, it is preferable that the layer be laminated on the corona-treated surface side. That is, when a laminate using the polyethylene film 100 of the present embodiment is used for a package (such as a food packaging bag), it is preferable that the polyethylene film 100 of the present embodiment side be the outermost layer of the package.

[0081] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various other configurations may be adopted. Furthermore, the present invention is not limited to the above-described embodiments, and modifications and improvements within the scope of achieving the object of the present invention are included in the present invention. [Example]

[0082] The present embodiment will be described in detail below with reference to examples and comparative examples, but the present embodiment is not limited to the descriptions of these examples.

[0083] <Raw materials> The raw materials used in the examples and comparative examples are shown below. The density was measured in accordance with JIS K 7112:1999. The MFR was measured in accordance with JIS K 7210:1999 under conditions of 190°C and a load of 2160g. The melting point was measured using a differential scanning calorimeter (DSC). Specifically, using a differential scanning calorimeter (product name: Q200DSC manufactured by TA Instruments), the first differential scanning calorimeter measurement consisted of a process of increasing the temperature from −50° C. to 230° C. at a rate of 10° C. / min and a process of decreasing the temperature from 230° C. to −50° C. at a rate of 10° C. / min under a nitrogen gas flow, and the second differential scanning calorimeter measurement consisted of a process of increasing the temperature from −50° C. to 230° C. at a rate of 10° C. / min. The peak temperature of the maximum endothermic peak in the second DSC curve was taken as the melting point (°C).

[0084] Linear low-density polyethylene 1 (LLDPE1), density: 0.918 g / cm 3, MFR: 3.8g / 10min, Melting point: 116℃ Linear low-density polyethylene 2 (LLDPE2), density: 0.928 g / cm 3 , MFR: 1.9g / 10min, Melting point: 126℃ Linear low-density polyethylene 3 (LLDPE3), density: 0.931 g / cm 3 , MFR: 3.2g / 10min, Melting point: 123℃ Linear low-density polyethylene 4 (LLDPE4), density: 0.937 g / cm 3 , MFR: 1.8g / 10min, Melting point: 127℃ High-density polyethylene 1 (HDPE1), density: 0.958 g / cm 3 , MFR: 1.0g / 10min, Melting point: 133℃ High-density polyethylene 2 (HDPE2), density: 0.949 g / cm 3 , MFR: 1.1g / 10min, Melting point: 130℃

[0085] <Production of polyethylene film> For Examples 1 to 5 and Comparative Example 1, polyethylene films were extruded to have the compositions and layer structures shown in Table 1, and then stretched under the conditions shown in Table 1 to produce the polyethylene films. Next, the surface on the surface resin layer 2 side in Table 1 was subjected to a corona treatment, and then aluminum was vapor-deposited on the corona-treated surface by heating and evaporating the aluminum using a high-frequency induction heating method, forming an aluminum film with a thickness of 40 nm. In this way, aluminum-vapor-deposited polyethylene films were produced. The obtained polyethylene films and aluminum-vapor-deposited polyethylene films were evaluated. The extrusion molding conditions and stretching conditions were as follows. Extrusion molding machine: 60 mmφ multi-layer T-die extrusion molding machine (screw: L / D=27, manufactured by Screw Seiki Co., Ltd.) Extrusion temperature setting: 230-250°C, Processing speed: 15m / min (winding speed) Stretching temperature in MD direction [°C]: See Table 1 Stretching ratio in MD direction [times]: See Table 1 Stretching temperature in TD direction [°C]: See Table 1 Stretching ratio in TD direction [times]: See Table 1 Relaxation rate [%]: See Table 1 Here, the relaxation rate refers to the maximum stretching width in the device settings divided by the tenter outlet width. In addition, the notation "A / B / C" for the stretching temperature in Table 1 means "preheating temperature (temperature at which the raw film is heated before stretching) / stretching temperature (temperature at which stretching is performed) / heat setting temperature (temperature at which heat setting (annealing) is performed after stretching)."

[0086] <Tensile modulus> A 15 mm x 15 cm test piece was cut from each aluminum-deposited polyethylene film. The MD and TD tensile moduli (T1, T2) of the test pieces were measured using an Orientec tensile tester in accordance with JIS K7127:1999 at a temperature of 23±2°C, 50±5% RH, and a pulling rate of 5 mm / min. The sum of T1 and T2 was calculated from the obtained values.

[0087] <Heat shrinkage rate of aluminum-coated polyethylene film at 100°C> The heat shrinkage rates of the aluminum-deposited polyethylene film in the MD and TD directions at 100°C were measured in accordance with JIS C2151:2019. A 10cm x 10cm test piece was cut out from the aluminum vapor-deposited polyethylene film of each example. Then, the test piece was heat-treated at 100°C for 15 minutes. At this time, the test piece was heated while hanging without applying force in a hot air circulation type thermostatic chamber (manufactured by ADVANTEC, product name: DRM620DE). Then, after cooling the test piece to room temperature, the length of the test piece was measured. The length in the MD direction of the test piece after heat treatment was measured as MD. 100 [cm], and the thermal shrinkage rate in the MD direction X MD100 [%] = 100 × (10 − MD 100 The length of the test piece in the TD direction after heat treatment was calculated as TD 100 [cm], and the thermal shrinkage rate in the TD direction X TD100 [%] = 100 × (10-TD 100) / 10. Each of the above measurements was carried out three times, and the average value of the obtained measurements was used as the heat shrinkage rate of the aluminum vapor-deposited polyethylene film at 100°C.

[0088] <Heat shrinkage rate of aluminum-coated polyethylene film at 120°C> The heat shrinkage rates of the aluminum-deposited polyethylene film in the MD and TD directions at 120°C were measured in accordance with JIS C2151:2019. A 10cm x 10cm test piece was cut out from the aluminum vapor-deposited polyethylene film of each example. Then, the test piece was heat-treated at 120°C for 15 minutes. At this time, the test piece was heated while hanging without applying force in a hot air circulation type thermostatic chamber (manufactured by ADVANTEC, product name: DRM620DE). Then, after cooling the test piece to room temperature, the length of the test piece was measured. The length in the MD direction of the test piece after heat treatment was measured as MD. 120 [cm], and the thermal shrinkage rate in the MD direction X MD120 [%] = 100 × (10 − MD 120 The length of the test piece in the TD direction after heat treatment was calculated as TD 120 [cm], and the thermal shrinkage rate in the TD direction X TD120 [%] = 100 × (10-TD 120 ) / 10. Each of the above measurements was carried out three times, and the average value of the obtained measurements was used as the heat shrinkage rate of the aluminum vapor-deposited polyethylene film at 120°C.

[0089] <Moisture permeability (water vapor permeability)> An adhesive (12 parts by mass of a polyester adhesive (Mitsui Chemicals, Inc., product name: Takelac A-310), 1 part by mass of an isocyanate curing agent (Mitsui Chemicals, Inc., product name: Takenate A-3), and 7 parts by mass of ethyl acetate) was applied to one side of a 50 μm-thick unstretched LLDPE film (manufactured by Mitsui Chemicals Tohcello, Inc.). The aluminum-vapor-deposited polyethylene film and the LLDPE film were then laminated (dry laminated) so that the inorganic layer side of the aluminum-vapor-deposited polyethylene film and the adhesive-coated surface of the LLDPE film were in contact with each other, yielding a multilayer film. The resulting multilayer film was then folded over so that the LLDPE film was on the inside, and the two sides were heat-sealed to form a bag. Calcium chloride was then placed inside the resulting bag. The other side of the bag was then heat-sealed to form a bag with a surface area of 0.01 m. 2 The bags were then stored at 40°C and 90% RH for 300 hours. The weight of the calcium chloride was measured before and after storage, and the moisture permeability was calculated from the difference.

[0090] <Oxygen permeability> In the same manner as in the moisture permeability measurement method, an aluminum-deposited polyethylene film and an LLDPE film were laminated to obtain a multilayer film. The oxygen permeability (mL / (m 2 The compressive strength (MPa) was measured using a Mocon OX-TRAN2 / 21 in accordance with JIS K7126:2006 at a temperature of 20°C and a humidity of 90%.

[0091] <Surface roughness> The arithmetic mean height Sa and developed area ratio Sdr of the corona-treated surface of the polyethylene film and the aluminum film surface of the aluminum-deposited polyethylene film were measured in accordance with ISO 25178 using a laser microscope (OLS5000) manufactured by Olympus Corporation. The polyethylene film and aluminum-deposited polyethylene film of each example were placed on an electrostatic suction stage with the surface to be measured facing up. Five samples were used, and the values in Table 1 were the average values. Measurement was performed under the following conditions. Objective lens: 50x Digital zoom: 1x Height range: 5 μm up and down Brightness: Automatic setting The measured images were analyzed under the following conditions. Evaluation area: All areas De-skew: Automatic Filter conditions: Shape removal settings, multidimensional surfaces, 2D Roughness parameters: surface area

[0092] [Table 1] [Explanation of symbols]

[0093] 100 Polyethylene film 101 film layer 103 Inorganic layer 105 Surface resin layer

Claims

1. a film layer containing an ethylene-based polymer; an inorganic layer containing an inorganic material on the film layer; Equipped with Heat shrinkage rate X in the MD direction when heat treated at 100°C for 15 minutes in accordance with JIS C2151:2019 ＭＤ１００ A polyethylene film having a modulus of elasticity of less than 5.0%.

2. Heat shrinkage rate X in the TD direction when heat treated at 100°C for 15 minutes in accordance with JIS C2151:2019 ＴＤ１００ and the heat shrinkage rate X ＭＤ１００ The polyethylene film according to claim 1, wherein the absolute value of the difference between the values is 5.0% or less.

3. The heat shrinkage rate X ＭＤ１００ to the heat shrinkage rate X ＴＤ１００ The polyethylene film according to claim 2, wherein the value obtained by subtracting

4. Heat shrinkage rate X in the TD direction when heat treated at 100°C for 15 minutes in accordance with JIS C2151:2019 ＴＤ１００ The polyethylene film according to any one of claims 1 to 3, wherein the tensile strength of the polyethylene film is 0.0% or more.

5. Heat shrinkage rate X in the MD direction when heat treated at 120°C for 15 minutes in accordance with JIS C2151:2019 ＭＤ１２０ The polyethylene film according to any one of claims 1 to 4, wherein the modulus of elasticity is less than 26.0%.

6. Heat shrinkage rate X in the TD direction when heat treated at 120°C for 15 minutes in accordance with JIS C2151:2019 ＴＤ１２０ and the heat shrinkage rate X in the MD direction when heat treated at 120°C for 15 minutes in accordance with JIS C2151:2019. ＭＤ１２０ The polyethylene film according to any one of claims 1 to 5, wherein the absolute value of the difference between

7. Heat shrinkage rate X in the MD direction when heat treated at 120°C for 15 minutes in accordance with JIS C2151:2019 ＭＤ１２０ The thermal shrinkage rate X in the TD direction when heat-treated at 120°C for 15 minutes in accordance with JIS C2151:2019 ＴＤ１２０ The polyethylene film according to any one of claims 1 to 6, wherein the value obtained by subtracting

8. Heat shrinkage rate X in the TD direction when heat treated at 120°C for 15 minutes in accordance with JIS C2151:2019 ＴＤ１２０ The polyethylene film according to any one of claims 1 to 7, wherein the content of hydroxybenzoates in the polyethylene film is 0.0% or more.

9. The tensile modulus T in the MD direction is measured in accordance with JIS K7127:1999 using a tensile tester under the conditions of a measurement temperature of 23±2°C, 50±5% RH, and a tensile speed of 5 mm / min. １ and the tensile modulus in the TD direction T ２ The polyethylene film according to any one of claims 1 to 8, wherein the total value of is 500 MPa or more and 9000 MPa or less.

10. The moisture permeability measured by the following method is 3.2 g / (m ２ The polyethylene film according to any one of claims 1 to 9, wherein the film thickness is 100 μm or less. (Measurement method) An adhesive is applied to one side of a 50 μm thick LLDPE film. The polyethylene film and the LLDPE film are then laminated together so that the inorganic layer side of the polyethylene film is in contact with the adhesive-coated side of the LLDPE film, yielding a multilayer film. The resulting multilayer film is then folded back so that the LLDPE film faces inward, and the two sides are heat-sealed to form a bag. Calcium chloride is then placed inside the resulting bag. The other side of the bag is then heat-sealed to reduce the surface area to 0.01 m. ２ The resulting bag is then stored for 300 hours under conditions of 40°C and 90% RH. The weight of the calcium chloride is measured before and after storage, and the moisture permeability is calculated from the difference.

11. The oxygen permeability measured by the following method is 800 mL / (m ２ The polyethylene film according to any one of claims 1 to 10, wherein the elongation coefficient is 0.5-1.5 MPa (day MPa) or less. (Measurement method) An adhesive is applied to one side of a 50 μm thick LLDPE film. Then, the polyethylene film and the LLDPE film are laminated together so that the inorganic layer side of the polyethylene film is in contact with the adhesive-coated side of the LLDPE film, thereby obtaining a multilayer film. The oxygen permeability (mL / (m ２ The thermal expansion coefficient (Tc) is measured in accordance with JIS K7126:2006 under conditions of 20°C and 90% RH.

12. The polyethylene film according to any one of claims 1 to 11, wherein the film layer comprises a uniaxially oriented film layer or a biaxially oriented film layer.

13. The polyethylene film according to any one of claims 1 to 12, wherein the content of the ethylene-based polymer in the film layer is 75% by mass or more and 100% by mass or less, when the entire film layer is taken as 100% by mass.

14. The polyethylene film according to any one of claims 1 to 13, wherein the ethylene-based polymer comprises polyethylene.

15. 15. The polyethylene film according to claim 14, wherein the polyethylene comprises one or more selected from the group consisting of low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), and high-density polyethylene (HDPE).

16. The density of the ethylene polymer is 0.910 g / cm ３ 0.970g / cm or more ３ The polyethylene film according to any one of claims 1 to 15, wherein:

17. The polyethylene film according to any one of claims 1 to 16, further comprising a surface resin layer on at least one surface of the film layer.

18. The polyethylene film according to claim 17, wherein the surface resin layer comprises an ethylene-based polymer.

19. 19. The polyethylene film according to claim 18, wherein the content of the ethylene polymer in the surface resin layer is 75% by mass or more and 100% by mass or less, when the entire surface resin layer is taken as 100% by mass.

20. The polyethylene film according to any one of claims 17 to 19, wherein the thickness of the surface resin layer is 0.1 µm or more and 10 µm or less.

21. The polyethylene film according to any one of claims 1 to 20, wherein the thickness of the film layer is 5 µm or more and 100 µm or less.

22. The polyethylene film according to any one of claims 1 to 21, wherein the ratio of the thickness of the film layer to the total thickness of the polyethylene film is 20% or more and less than 100%.

23. The polyethylene film according to any one of claims 1 to 22, wherein the arithmetic mean height Sa of the film layer at the surface, measured in accordance with ISO 25178, is less than 0.50 µm.

24. The polyethylene film according to any one of claims 1 to 23, wherein the inorganic layer has an arithmetic mean height Sa at the surface, measured in accordance with ISO 25178, of less than 0.50 µm.

25. The polyethylene film according to any one of claims 1 to 24, wherein the developed area ratio Sdr on the surface of the film layer, measured in accordance with ISO 25178, is less than 4.90%.

26. The polyethylene film according to any one of claims 1 to 25, wherein the inorganic layer has a developed area ratio Sdr on the surface thereof, as measured in accordance with ISO 25178, of less than 5.20%.

27. The polyethylene film according to any one of claims 1 to 26, which is a packaging film.

28. A packaging material comprising the polyethylene film according to any one of claims 1 to 27.

29. 30. The packaging material of claim 28, further comprising a coating layer on at least one side of the polyethylene film.

30. A packaging material according to claim 28 or 29; and an item within the packaging material.

Images