Packaging material and pouch comprising packaging material

Abstract

To provide a packaging material which is excellent in the shatter strength and the sticking strength.SOLUTION: A packaging material includes at least a first biaxially-oriented plastic film, a second biaxially-oriented plastic film and a sealant layer sequentially from the outer surface side to the inner surface side. The first biaxially-oriented plastic film and the second biaxially-oriented plastic film include polyester as a main component. The loop stiffness in one direction of the packaging material is less than 0.150 N and the sticking strength of the packaging material is equal to or greater than 14.0 N.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to packaging materials and pouches comprising packaging materials. [Background technology]

[0002] Conventionally, various packaging materials have been developed and proposed as packaging materials for constituting packaged products in which various items such as food and beverages, pharmaceuticals, chemicals, cosmetics, hygiene products, daily necessities, etc. are filled and packaged. The packaging materials include a plastic film as a substrate. For example, Patent Document 1 discloses an example in which the packaging material includes two substrates each including polyethylene terephthalate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Utility Model Application Publication No. 2-8784 Summary of the Invention [Problem to be solved by the invention]

[0004] Packaging materials are sometimes required to have drop strength and puncture strength. Drop strength is necessary to prevent damage such as tearing of the packaging material when a packaging container containing the packaging material is dropped. Puncture strength is necessary to prevent the packaging container from being torn when it comes into contact with a sharp object with a pointed tip. Packaging materials containing two base materials containing polyethylene terephthalate, such as those described in Patent Document 1, sometimes have insufficient puncture strength.

[0005] The present invention has been made in consideration of the above points, and an object of the present invention is to provide a packaging material that is excellent in drop strength and puncture resistance. [Means for solving the problem]

[0006] The present invention is a packaging material comprising, in order from the outer surface side to the inner surface side, at least a first biaxially oriented plastic film, a second biaxially oriented plastic film, and a sealant layer, wherein the first biaxially oriented plastic film and the second biaxially oriented plastic film contain polyester as a primary component, the loop stiffness in one direction of the packaging material is less than 0.150 N, and the puncture strength of the packaging material is 14.0 N or more.

[0007] In the packaging material according to the present invention, both the first biaxially oriented plastic film and the second biaxially oriented plastic film may contain polyethylene terephthalate as a main component.

[0008] The packaging material according to the present invention may be provided with a printed layer.

[0009] The packaging material according to the present invention may comprise a vapor deposition layer located on the surface of the first biaxially oriented plastic film or the surface of the second biaxially oriented plastic film, and a gas barrier coating film located on the vapor deposition layer.

[0010] In the packaging material according to the present invention, the packaging material may have a puncture strength of 16.0 N or more.

[0011] In the packaging material according to the present invention, the sealant layer may contain polypropylene as a main component.

[0012] In the packaging material according to the present invention, the sealant layer may contain polyethylene having a melting point of 100°C or higher.

[0013] In the packaging material according to the present invention, the sealant layer may have a first layer mainly composed of polyethylene or polypropylene, and a second layer located on the inner side of the first layer and containing a mixed resin of polyethylene and polypropylene.

[0014] The packaging material according to the present invention is a retort pouch comprising the packaging material described above.

[0015] The packaging material according to the present invention is a microwave pouch having a storage section, comprising the packaging material described above and a seal section joining the inner surfaces of the packaging material together, the seal section including a steam release seal section configured to be peeled apart by an increase in pressure in the storage section. [Effects of the Invention]

[0016] According to the present invention, a packaging material having excellent drop strength and puncture resistance can be provided. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a front view showing a bag according to an embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing an example of the layer structure of a packaging material that constitutes a bag. [Figure 3] FIG. 10 is a cross-sectional view showing a modified example of the layer structure of the packaging material that constitutes the bag. [Figure 4] FIG. 10 is a cross-sectional view showing a modified example of the layer structure of the packaging material that constitutes the bag. [Figure 5] FIG. 1 is a plan view showing an example of a loop stiffness measuring device. [Figure 6] FIG. 6 is a cross-sectional view of the loop stiffness measuring device of FIG. 5 taken along line VI-VI. [Figure 7] FIG. 10 is a diagram showing an example of a method for preparing a test piece used in a loop stiffness measuring device. [Figure 8] FIG. 10 is a diagram illustrating a process of attaching a test piece to a loop stiffness measuring instrument. [Figure 9] FIG. 10 is a diagram illustrating a step of forming a loop portion in a test piece. [Figure 10] FIG. 10 is a diagram illustrating a process of applying a load to a loop portion of a test piece. [Figure 11]FIG. 10 is a diagram illustrating a process of applying a load to a loop portion of a test piece. [Figure 12] FIG. 2 is a diagram showing an example of a layer structure of a sealant layer. [Figure 13] FIG. 1 shows an example of the results of analyzing a transparent vapor-deposited layer formed on the surface of a biaxially stretched plastic film using a time-of-flight secondary ion mass spectrometer. [Figure 14] 10A and 10B are diagrams showing an example of a method for filling a bag with contents. [Figure 15] FIG. 10 is a front view showing a modified example of the bag. [Figure 16] FIG. 10 is a front view showing a modified example of the bag. [Figure 17] FIG. 10 is a front view showing a modified example of the bag. [Figure 18A] 1 is a longitudinal cross-sectional view showing an example of a container containing packaging material. [Figure 18B] FIG. 1 is a plan view illustrating an example of a container containing packaging material. [Figure 19] FIG. 10 is a diagram showing an example of a method for measuring puncture strength. [Figure 20] FIG. 1 is a diagram showing the evaluation results of Examples A1 to A3. [Figure 21] FIG. 1 is a diagram showing the evaluation results of Comparative Examples 1 to 3. [Figure 22] FIG. 1 is a diagram showing the evaluation results of Examples B1 to B3. [Figure 23] FIG. 1 is a diagram showing the evaluation results of Examples C1 to C3. DETAILED DESCRIPTION OF THE INVENTION

[0018] An embodiment of the present invention will be described with reference to Figures 1 to 14. In the drawings accompanying this specification, the scale and aspect ratios have been appropriately changed and exaggerated from those of the actual objects for the sake of ease of illustration and understanding.

[0019] Furthermore, terms used in this specification that specify shapes, geometric conditions, and their degrees, such as "parallel," "orthogonal," and "identical," as well as values ​​of lengths and angles, are not to be construed as being bound by strict meanings, but rather as including a range within which similar functions can be expected.

[0020] Fig. 1 is a front view showing bag 10 according to the present embodiment. Bag 10 includes a storage section 17 for storing contents. Fig. 1 shows bag 10 in a state before the contents are stored in it. The configuration of bag 10 will be described below.

[0021] bag In this embodiment, bag 10 is a so-called flat pouch made by joining a film on the front side of bag 10 with a film on the back side. Bag 10 includes an upper portion 11, a lower portion 12, and a pair of side portions 13, and has a generally rectangular outline in a front view. Note that names such as "upper portion," "lower portion," and "side portion," as well as terms such as "above" and "below," merely describe the relative positions and directions of bag 10 and its components with respect to a state in which the opening for filling the contents is located at the top. The position of bag 10 during transportation or use is not limited by the names and terms used in this specification.

[0022] In this embodiment, the width direction of bag 10 is also referred to as first direction D1. The pair of side portions 13 described above face each other in first direction D1. The direction perpendicular to first direction D1 is also referred to as second direction D2. Bag 10 of this embodiment is intended to be used in such a way that a consumer tears bag 10 along first direction D1 to open bag 10.

[0023] As shown in FIG. 1, the bag 10 includes a surface film 14 that forms the surface, and a back film 15 that forms the back.

[0024] The terms "surface film" and "back surface film" mentioned above merely distinguish between the films according to their positional relationships, and the terms do not limit the method of providing the films when manufacturing bag 10. For example, bag 10 may be manufactured using a single film in which surface film 14 and back surface film 15 are continuously disposed, or may be manufactured using a total of two films: one surface film 14 and one back surface film 15.

[0025] The inner surfaces of the front film 14 and the back film 15 are joined together by a seal portion. In a front view of the bag 10 such as Figure 1, the seal portion is hatched.

[0026] As shown in Figure 1, the seal portion has an outer edge seal portion that extends along the outer edge of bag 10. The outer edge seal portion includes a bottom seal portion 12a that extends along bottom portion 12, and a pair of side seal portions 13a that extend along a pair of side portions 13. Before contents are placed inside bag 10, as shown in Figure 1, top 11 of bag 10 forms opening 11b. After contents are placed inside bag 10, the inner surfaces of front film 14 and back film 15 are joined at top 11 to form the top seal portion and seal bag 10.

[0027] The bottom seal portion 12a, the side seal portion 13a, and the top seal portion are seal portions formed by joining the inner surface of the front film 14 and the inner surface of the back film 15 together.

[0028] There are no particular limitations on the method for forming the seal portion, as long as it is possible to join opposing films together and seal bag 10. For example, the seal portion may be formed by melting the inner surfaces of the films by heating or the like, welding the inner surfaces together, i.e., by heat sealing. Alternatively, the seal portion may be formed by bonding the inner surfaces of opposing films together using an adhesive or the like.

[0029] Easy-to-open means The front film 14 and the back film 15 may be provided with easy-open means 25 for tearing the front film 14 and the back film 15 along the first direction D1 to open the bag 10. For example, as shown in Fig. 1, the easy-open means 25 may include a notch 26 formed in the side seal portion 13a of the bag 10, which serves as a starting point for tearing. Alternatively, the easy-open means 25 may be a half-cut line formed by laser processing, a cutter, or the like, in a portion that serves as a path for tearing the bag 10.

[0030] Furthermore, although not shown, the easy-open means 25 may include a group of cuts or scars formed in the area where the seal portion is formed of the front film 14 and the back film 15. The group of scars may include, for example, a plurality of through holes formed so as to penetrate the front film 14 and / or the back film 15. Alternatively, the group of scars may include a plurality of holes formed on the outer surface of the front film 14 and / or the back film 15 so as not to penetrate the front film 14 and / or the back film 15.

[0031] Layer structure of surface film and back film Next, a description will be given of the layer structure of the front film 14 and the back film 15. Fig. 2 is a cross-sectional view showing an example of the layer structure of a packaging material 30 that constitutes the front film 14 and the back film 15.

[0032] 2, the packaging material 30 comprises at least a first biaxially oriented plastic film 40, a first adhesive layer 45, a second biaxially oriented plastic film 50, a second adhesive layer 55, and a sealant layer 70, in this order. The first biaxially oriented plastic film 40 is located on the outer surface 30y side, and the sealant layer 70 is located on the inner surface 30x side opposite the outer surface 30y. The inner surface 30x is the surface located on the storage section 17 side.

[0033] Each film constituting the packaging material 30, such as the first biaxially oriented plastic film 40 and the second biaxially oriented plastic film 50, and the packaging material 30 have a machine direction and a perpendicular direction. When the sealant layer 70 is composed of a sealant film, the sealant layer 70 also has a machine direction and a perpendicular direction. The machine direction is the direction in which the film flows when formed, and is known as the MD (Machine Direction). The perpendicular direction is the direction perpendicular to the machine direction, and is known as the TD (Transverse Direction). In the bag 10 shown in FIG. 1, the direction in which the upper portion 11 and the lower portion 12 extend is the machine direction, and the direction in which the side portion 13 extends is the perpendicular direction.

[0034] The packaging material 30 of this embodiment is configured to have excellent puncture strength. This makes it possible to prevent the bag 10 from being torn when it comes into contact with a sharp member having a pointed tip. That is, a packaged product such as the bag 10 made from the packaging material 30 can have puncture resistance. The packaging material 30 of this embodiment is also configured to have excellent drop strength. This makes it possible to prevent damage such as tearing of the packaging material when a packaging container containing the packaging material is dropped. That is, a packaged product such as the bag 10 made from the packaging material 30 can have impact resistance.

[0035] Each layer of packaging material 30 will now be described in detail.

[0036] (biaxially oriented plastic film) Both the first biaxially stretched plastic film 40 and the second biaxially stretched plastic film 50 are biaxially stretched films stretched in two predetermined directions. A biaxially stretched plastic film is a plastic film that has been intentionally stretched to improve the mechanical strength of the plastic film. The stretching direction of each biaxially stretched plastic film 40, 50 is not particularly limited. For example, the biaxially stretched plastic films 40, 50 may be stretched in the direction in which the side portions 13 extend and in a direction perpendicular to the direction in which the side portions 13 extend. Furthermore, the stretching directions of each biaxially stretched plastic film 40, 50 may be the same or different. The stretching ratio of each biaxially stretched plastic film 40, 50 is, for example, 1.05 times or more.

[0037] In this embodiment, we propose using a biaxially oriented plastic film having a loop stiffness of 0.0017 N or more in at least one direction and containing polyester as a primary component as either the first biaxially oriented plastic film 40 or the second biaxially oriented plastic film 50. In the following description, a biaxially oriented plastic film having a loop stiffness of 0.0017 N or more in at least one direction and containing polyester as a primary component is also referred to as a high-stiffness polyester film. A high-stiffness polyester film may have a loop stiffness of 0.0017 N or more in at least one of the machine direction (MD) and the transverse direction (TD). A high-stiffness polyester film may have a loop stiffness of 0.0017 N or more in both the machine direction (MD) and the transverse direction (TD). By including a high-stiffness polyester film in the packaging material 30, the packaging material 30 can have excellent puncture strength. In this application, the term "main component" refers to a component that accounts for 51% by mass. The high stiffness polyester film does not contain polyamide. The polyester is preferably a polyester primarily composed of an aromatic polyester consisting of at least one aromatic dicarboxylic acid selected from terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid and at least one aliphatic alcohol selected from ethylene glycol, 1,3-propanediol, and 1,4-butanediol. Examples of polyesters include polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). Examples of high-stiffness polyester films include high-stiffness PET films containing 51% by mass or more of PET as the main component, and high-stiffness PBT films containing 51% by mass or more of PBT as the main component. The thickness of the high-stiffness polyester film is preferably 5 μm or more, more preferably 7 μm or more. The thickness of the high-stiffness polyester film is preferably 25 μm or less, more preferably 20 μm or less.

[0038] Loop stiffness is a parameter that represents the stiffness of a film such as a biaxially stretched plastic film. A method for measuring loop stiffness will be described below with reference to FIGS. 5 to 11. The measurement method described below can be used not only for single-layer films such as biaxially stretched plastic films, but also for films with multiple layers, such as vapor-deposited films and laminated films. A vapor-deposited film is a film that includes a single-layer film such as a biaxially stretched plastic film and a vapor-deposited layer formed on the single-layer film. A laminated film is a film that includes multiple laminated films, such as packaging material 30.

[0039] FIG. 5 is a plan view showing the test piece 80 and the loop stiffness measuring device 85, and FIG. 6 is a cross-sectional view of the test piece 80 and the loop stiffness measuring device 85 of FIG. 5 taken along line VI-VI. The test piece 80 is a rectangular film having long and short sides. In the present application, the length L1 of the long side of the test piece 80 is 150 mm, and the length L2 of the short side is 15 mm. As the loop stiffness measuring device 85, for example, No. 581 Loop Stiffness Tester (registered trademark) LOOP STIFFNESS TESTER DA type manufactured by Toyo Seiki Seisakusho, Ltd. can be used. The length L1 of the long side of the test piece 80 is adjustable as long as the test piece 80 can be gripped by a pair of chucks 86, which will be described later.

[0040] The loop stiffness measuring device 85 has a pair of chuck portions 86 for gripping a pair of ends in the long side direction of the test specimen 80, and a support member 87 for supporting the chuck portions 86. The chuck portions 86 include a first chuck 861 and a second chuck 862. In the state shown in FIGS. 5 and 6 , the test specimen 80 is placed on the pair of first chucks 861, and the second chuck 862 has not yet gripped the test specimen 80 between the first chuck 861 and the second chuck 862. As will be described later, during measurement, the test specimen 80 is gripped between the first chuck 861 and the second chuck 862 of the chuck portions 86. The second chuck 862 may be connected to the first chuck 861 via a hinge mechanism.

[0041] When a film to be measured, such as a biaxially oriented plastic film, a vapor-deposited film, or a laminated film, is available in a state before being processed into a packaging product, the test piece 80 may be prepared by cutting the film to be measured. Alternatively, the test piece 80 may be prepared by cutting a packaging product made from the packaging material 30, such as a bag. FIG. 7 shows an example of a method for preparing the test piece 80 by cutting the surface film 14 or the back film 15 of the bag 10. When measuring the loop stiffness of the packaging material 30 in the machine direction, the test piece is prepared by cutting the surface film 14 or the back film 15 of the bag 10 so that the long side direction of the test piece coincides with the machine direction, as shown by reference numeral 80A in FIG. 7. When measuring the loop stiffness of the packaging material 30 in the vertical direction, the test piece is prepared by cutting the surface film 14 or the back film 15 of the bag 10 so that the long side direction of the test piece coincides with the vertical direction, as shown by reference numeral 80B in FIG. 7.

[0042] A method for measuring the loop stiffness of the test piece 80 using the loop stiffness measuring device 85 will be described. First, as shown in FIGS. 5 and 6 , the test piece 80 is placed on a first chuck 861 of a pair of chucks 86 arranged with a gap L3 therebetween. In the present application, the gap L3 is set so that the length of a loop portion 81 (described later, also referred to as the loop length) is 60 mm. The test piece 80 includes an inner surface 80x located on the first chuck 861 side and an outer surface 80y located opposite the inner surface 80x. When the test piece 80 is made of a packaging material 30, the inner surface 80x and the outer surface 80y of the test piece 80 coincide with the inner surface 30x and the outer surface 30y of the packaging material 30. When a loop portion 81 (described later) is formed in the test piece 80, the inner surface 80x is located inside the loop portion 81, and the outer surface 80y is located outside the loop portion 81. Next, as shown in FIG. 8, the second chuck 862 is placed on the test piece 80 so that the end of the long side of the test piece 80 is gripped between the first chuck 861 and the second chuck 862.

[0043] Next, as shown in FIG. 9 , at least one of the pair of chuck portions 86 is slid on the support member 87 in a direction that reduces the distance between the pair of chuck portions 86. This allows a loop portion 81 to be formed on the test piece 80. The test piece 80 shown in FIG. 9 has a loop portion 81, a pair of intermediate portions 82, and a pair of fixing portions 83. The pair of fixing portions 83 are portions of the test piece 80 that are gripped by the pair of chuck portions 86. The pair of intermediate portions 82 are portions of the test piece 80 that are located between the loop portion 81 and the pair of intermediate portions 82. As shown in FIG. 9 , the chuck portion 86 is slid on the support member 87 until the inner surfaces 80x of the pair of intermediate portions 82 come into contact with each other. This allows a loop portion 81 having a loop length of 60 mm to be formed. The loop length of the loop portion 81 is the length of the test piece 80 between position P1 where the surface of one second chuck 862 on the loop portion 81 side intersects with the test piece 80, and position P2 where the surface of the other second chuck 862 on the loop portion 81 side intersects with the test piece 80. If the thickness of the test piece 80 is ignored, the above-mentioned distance L3 is the value obtained by adding 2×t to the length of the loop portion 81, where t is the thickness of the second chuck 862 of the chuck portion 86.

[0044] Then, as shown in FIG. 10 , the posture of the chuck portion 86 is adjusted so that the protruding direction Y of the loop portion 81 relative to the chuck portion 86 is horizontal. For example, the posture of the chuck portion 86 supported by the support member 87 is adjusted by moving the support member 87 so that the normal direction of the support member 87 is horizontal. In the example shown in FIG. 10 , the protruding direction Y of the loop portion 81 coincides with the thickness direction of the chuck portion. Furthermore, a load cell 88 is prepared at a position a distance Z1 away from the second chuck 862 in the protruding direction Y of the loop portion 81. In this application, the distance Z1 is set to 50 mm. Next, the load cell 88 is moved toward the loop portion 81 of the test piece 80 at a speed V by a distance Z2 shown in FIG. 10 . The distance Z2 is set so that the load cell 88 contacts the loop portion 81 and then pushes the loop portion 81 toward the chuck portion 86, as shown in FIGS. 10 and 11 . In this application, the distance Z2 is set to 40 mm. In this case, the distance Z3 between the load cell 88 and the second chuck 862 of the chuck portion 86 is 10 mm when the load cell 88 is pressing the loop portion 81 toward the chuck portion 86. The speed V at which the load cell 88 is moved is 3.3 mm / sec.

[0045] Next, as shown in Fig. 11, the load cell 88 is moved a distance Z2 toward the chuck portion 86, and in a state where the load cell 88 is pressing into the loop portion 81 of the test piece 80, the value of the load applied to the load cell 88 from the loop portion 81 becomes stable, and then the value of the load is recorded. The value of the load thus obtained is used as the loop stiffness of the film constituting the test piece 80. In this application, unless otherwise specified, the environment during measurement of loop stiffness is a temperature of 23°C and a relative humidity of 50%.

[0046] The preferred mechanical properties of the high stiffness polyester film will be further described. The puncture strength of the high stiffness polyester film is preferably 10 N or more, and more preferably 11 N or more.

[0047] The tensile strength of the high-stiffness polyester film in at least one direction is preferably 250 MPa or more, more preferably 280 MPa or more. For example, the tensile strength of the high-stiffness polyester film in the machine direction is preferably 250 MPa or more, more preferably 280 MPa or more. The tensile strength of the high-stiffness polyester film in the perpendicular direction is preferably 250 MPa or more, more preferably 280 MPa or more. The tensile elongation of the high stiffness polyester film in at least one direction is preferably 130% or less, more preferably 120% or less. For example, the tensile elongation of the high stiffness polyester film in the machine direction is preferably 130% or less, more preferably 120% or less. The tensile elongation of the high stiffness polyester film in the perpendicular direction is preferably 120% or less, more preferably 110% or less. Preferably, the tensile strength of the high-stiffness polyester film divided by the tensile elongation in at least one direction is 2.0 [MPa / %] or more. For example, the tensile strength of the high-stiffness polyester film divided by the tensile elongation in the transverse direction (TD) is preferably 2.0 [MPa / %] or more, more preferably 2.2 [MPa / %] or more. The tensile strength of the high-stiffness polyester film divided by the tensile elongation in the machine direction (MD) is preferably 1.8 [MPa / %] or more, more preferably 2.0 [MPa / %] or more.

[0048] The tensile strength and tensile elongation can be measured in accordance with JIS K7127. A tensile tester STA-1150 manufactured by Orientec Co., Ltd. can be used as a measuring instrument. A rectangular film cut from a high-stiffness polyester film with a width of 15 mm and a length of 150 mm can be used as a test piece. The distance between the pair of chucks holding the test piece at the start of measurement is 100 mm, and the tensile speed is 300 mm / min. The length of the test piece can be adjusted as long as the test piece can be held by the pair of chucks. Unless otherwise specified, the environment during measurement of the tensile strength and tensile elongation is a temperature of 23°C and a relative humidity of 50%. The tensile strength and tensile elongation of the packaging material 30 are measured in the same manner as for the high-stiffness polyester film, except that an Orientec RTC-1310A tensile tester is used as the measuring instrument and the distance between the pair of chucks holding the test piece is 50 mm at the start of the measurement. When measuring the tensile strength and tensile elongation of the packaging material 30, a test piece can be prepared by cutting the front film 14 or back film 15 of the bag 10 so that the long side direction of the test piece coincides with the machine direction or perpendicular to the machine direction, as in the case of measuring the loop stiffness shown in Figure 7.

[0049] The heat shrinkage of the high stiffness polyester film in at least one direction is preferably 0.7% or less, more preferably 0.5% or less. For example, the heat shrinkage of the high stiffness polyester film in the machine direction is preferably 0.7% or less, more preferably 0.5% or less. The heat shrinkage of the high stiffness polyester film in the perpendicular direction is preferably 0.7% or less, more preferably 0.5% or less. The heating temperature for measuring the heat shrinkage is 100°C, and the heating time is 40 minutes. The Young's modulus of the high-stiffness polyester film in at least one direction is preferably 4.0 GPa or more, more preferably 4.5 MPa or more. For example, the Young's modulus of the high-stiffness polyester film in the machine direction is preferably 4.0 GPa or more, more preferably 4.5 MPa or more. The Young's modulus of the high-stiffness polyester film in the perpendicular direction is preferably 4.0 GPa or more, more preferably 4.5 GPa or more.

[0050] Like tensile strength and tensile elongation, Young's modulus can be measured in accordance with JIS K7127. A tensile tester STA-1150 manufactured by Orientec Co., Ltd. can be used as a measuring instrument. A rectangular film cut from a high-stiffness polyester film with a width of 15 mm and a length of 150 mm can be used as a test piece. The distance between the pair of chucks holding the test piece at the start of measurement is 100 mm, and the tensile speed is 300 mm / min. The length of the test piece can be adjusted as long as the test piece can be held by the pair of chucks. Unless otherwise specified in this application, the environment during measurement of Young's modulus is a temperature of 23°C and a relative humidity of 50%. The Young's modulus of the packaging material 30 is measured in the same manner as for the high-stiffness polyester film, except that the measuring instrument is an Orientec RTC-1310A tensile tester, and the distance between the pair of chucks holding the test piece is 50 mm at the start of the measurement. When measuring the Young's modulus of the packaging material 30, a test piece can be prepared by cutting the front film 14 or back film 15 of the bag 10 so that the long side direction of the test piece coincides with the flow direction or the perpendicular direction, as in the case of measuring the loop stiffness shown in Figure 7.

[0051] In the packaging material 30 including a high-stiffness polyester film, the high-stiffness polyester film may be provided with a vapor-deposited layer 34, which will be described later. In this case, the high-stiffness polyester film provided with the vapor-deposited layer 34 may have mechanical properties equivalent to those of a single high-stiffness polyester film. For example, the high-stiffness polyester film provided with the vapor-deposited layer 34 may have a loop stiffness of 0.0017 N or more in at least one direction.

[0052] As described below, a gas barrier coating film 36 may be provided on the vapor deposition layer 34. In this case, the high stiffness polyester film provided with the vapor deposition layer 34 and the gas barrier coating film 36 may have mechanical properties equivalent to those of a single high stiffness polyester film. For example, the high stiffness polyester film provided with the vapor deposition layer 34 and the gas barrier coating film 36 may have a loop stiffness of 0.0017 N or more in at least one direction.

[0053] In the manufacturing process of a high-stiffness polyester film, for example, a plastic film obtained by melting and molding a polyester is first stretched 3 to 4.5 times in both the machine direction and the perpendicular direction at 90 to 145°C in a first stretching step. This is followed by a second stretching step in which the plastic film is stretched 1.1 to 3.0 times in both the machine direction and the perpendicular direction at 100 to 145°C in a second stretching step. This is followed by heat setting at 190 to 220°C. This is followed by relaxation treatment (treatment to reduce the film width) at 100 to 190°C in both the machine direction and the perpendicular direction at approximately 0.2 to 2.5%. By adjusting the stretch ratio, stretching temperature, heat setting temperature, and relaxation treatment rate in these steps, a high-stiffness polyester film having the above-mentioned mechanical properties can be obtained.

[0054] According to this embodiment, the packaging material 30 contains a high-stiffness polyester film, which imparts excellent puncture strength to the packaging material 30 and to packaged products such as bags 10 made from the packaging material 30. This makes it possible to prevent the bag 10 from being torn when a sharp object with a pointed tip comes into contact with the bag 10, for example. The puncture strength of the packaging material 30 is preferably 14.0 N or more, more preferably 15.0 N or more, more preferably 16.0 N or more, more preferably 17.0 N or more, more preferably 18.0 N or more, and even more preferably 19.0 N or more. A method for measuring the puncture strength will be described in the examples below.

[0055] Furthermore, according to the present embodiment, the packaging material 30 includes a high-stiffness polyester film, thereby increasing the Young's modulus of the packaging material 30. The Young's modulus of the packaging material 30 in one direction is, for example, 3200 MPa or more, or may be 3300 MPa or more, 3400 MPa or more, 3500 MPa or more, 3600 MPa or more, or 3700 MPa or more. The Young's modulus of the packaging material 30 in a direction perpendicular to the above-mentioned one direction is, for example, 2700 MPa or more, 2800 MPa or more, 2900 MPa or more, 3000 MPa or more, 3100 MPa or more, or 3200 MPa or more. For example, the Young's modulus of the packaging material 30 in the machine direction (MD) may be, for example, 3200 MPa or more, 3300 MPa or more, 3400 MPa or more, 3500 MPa or more, 3600 MPa or more, or 3700 MPa or more. Furthermore, the Young's modulus of the packaging material 30 in the transverse direction (TD), which is the direction perpendicular to the machine direction (MD), is, for example, 2700 MPa or more, and may be 2800 MPa or more, 2900 MPa or more, 3000 MPa or more, 3100 MPa or more, or 3200 MPa or more. A high Young's modulus of the packaging material 30 makes the packaging material 30 less likely to stretch. This increases the processing accuracy when processing the packaging material 30 in the manufacturing process of packaged products such as bags 10. Furthermore, when the packaging material 30 is used to produce a gusseted bag 10 configured to be self-standing, as described below, the self-standing ability of the bag 10 is improved.

[0056] In this embodiment, the loop stiffness of the packaging material 30 in at least one direction is, for example, 0.100 N or more, or may be 0.110 N or more, or may be 0.120 N or more. For example, the loop stiffness of the packaging material 30 in the machine direction (MD) is, for example, 0.100 N or more, or may be 0.110 N or more, or may be 0.120 N or more. Furthermore, the loop stiffness of the packaging material 30 in the transverse direction (TD) is, for example, 0.100 N or more, or may be 0.110 N or more, or may be 0.120 N or more.

[0057] On the other hand, if the loop stiffness of the packaging material 30 is too high, the packaging material 30 may be more susceptible to damage, such as tearing, when a packaged product made of the packaging material 30 is dropped. In consideration of this, the loop stiffness of the packaging material 30 in at least one direction may be less than 0.150 N, less than 0.140 N, or less than 0.130 N. For example, the loop stiffness of the packaging material 30 in the machine direction (MD) may be less than 0.150 N, less than 0.140 N, or less than 0.130 N. Furthermore, the loop stiffness of the packaging material 30 in the transverse direction (TD) may be less than 0.150 N, less than 0.140 N, or less than 0.130 N.

[0058] When the high-stiffness polyester film is a high-stiffness PET film containing PET as a main component, the PET constituting the high-stiffness PET film may contain biomass-derived PET. In this case, the high-stiffness PET film may be composed solely of biomass-derived PET. Alternatively, the high-stiffness PET film may be composed of biomass-derived PET and fossil fuel-derived PET. By including biomass-derived PET in the high-stiffness PET film, the amount of fossil fuel-derived PET can be reduced compared to conventional methods, thereby reducing carbon dioxide emissions and environmental impact. Note that biomass-derived PET has biomass-derived ethylene glycol as the diol unit and fossil fuel-derived terephthalic acid as the dicarboxylic acid unit. Fossil fuel-derived PET has fossil fuel-derived ethylene glycol as the diol unit and fossil fuel-derived terephthalic acid as the dicarboxylic acid unit.

[0059] Atmospheric carbon dioxide contains a certain proportion of C14 (105.5 pMC), and it is known that the C14 content in plants that grow by absorbing atmospheric carbon dioxide, such as corn, is also approximately 105.5 pMC. It is also known that fossil fuels contain very little C14. Therefore, the proportion of biomass-derived carbon can be calculated by measuring the proportion of C14 in the total carbon atoms in PET. In this specification, "biomass ratio" refers to the weight ratio of biomass-derived components. Taking PET as an example, PET is a polymer formed by polymerizing ethylene glycol containing two carbon atoms and terephthalic acid containing eight carbon atoms in a 1:1 molar ratio. If only biomass-derived ethylene glycol is used in PET, the weight ratio of biomass-derived components in PET is 31.25%, and the theoretical biomass ratio of PET is 31.25%. Specifically, the mass of PET is 192, of which 60 is derived from biomass-derived ethylene glycol, so 60 ÷ 192 × 100 = 31.25. Furthermore, the weight ratio of biomass-derived components in fossil fuel-derived PET is 0%, and the biomass content of fossil fuel-derived PET is 0%. In the present invention, the biomass content of the high-stiffness PET film is preferably 5.0% or more, and more preferably 10.0% or more. Furthermore, the biomass content of the high-stiffness PET film is preferably 30.0% or less.

[0060] Biomass-derived ethylene glycol is made from ethanol produced from biomass (biomass ethanol). For example, biomass-derived ethylene glycol can be obtained by converting biomass ethanol into ethylene oxide by a conventionally known method to produce ethylene glycol. Examples of raw materials for biomass ethanol include corn, sugarcane, beet, and manioc. Commercially available biomass ethylene glycol may also be used; for example, biomass ethylene glycol commercially available from India Glycoal Limited can be suitably used. Note that India Glycoal's biomass ethylene glycol is made from sugarcane molasses.

[0061] When one of the first biaxially oriented plastic film 40 or the second biaxially oriented plastic film 50 is a high-stiffness polyester film, the other of the first biaxially oriented plastic film 40 or the second biaxially oriented plastic film 50 contains polyester as a primary component. For example, when the first biaxially oriented plastic film 40 is a high-stiffness polyester film, the second biaxially oriented plastic film 50 may be a biaxially oriented plastic film containing polyester as a primary component. Furthermore, when the second biaxially oriented plastic film 50 is a high-stiffness polyester film, the first biaxially oriented plastic film 40 may be a biaxially oriented plastic film containing polyester as a primary component. Furthermore, both the first biaxially oriented plastic film 40 and the second biaxially oriented plastic film 50 may be high-stiffness polyester films. By having the other of the first biaxially oriented plastic film 40 or the second biaxially oriented plastic film 50 contain polyester as its main component, the bag 10 can be made heat resistant to high-temperature sterilization processes such as boiling and retort processing.

[0062] Biaxially stretched plastic films containing polyester as a primary component (hereinafter also referred to as biaxially stretched polyester films) contain, for example, 51% by mass or more of polyester. As with high-stiffness polyester films, the polyester is preferably a polyester primarily composed of an aromatic polyester consisting of at least one aromatic dicarboxylic acid selected from terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid and at least one aliphatic alcohol selected from ethylene glycol, 1,3-propanediol, and 1,4-butanediol. Examples of polyesters include PET and PBT. For example, a biaxially stretched polyester film may contain 51% by mass or more of PET as a primary component, or 51% by mass or more of PBT as a primary component. In a biaxially stretched polyester film, the 51% by mass or more of polyester may be composed of one type of polyester or two or more types of polyester. A biaxially stretched polyester film does not contain polyamide.

[0063] The preferred mechanical properties of the biaxially oriented polyester film will be further described. The Young's modulus of the biaxially oriented polyester film in at least one direction is preferably 3000 MPa or more. For example, the Young's modulus of the biaxially oriented polyester film in the machine direction and the perpendicular direction is preferably 3000 MPa or more. The tensile elongation of the biaxially oriented polyester film in at least one direction is preferably 200% or less. For example, the tensile elongation of the biaxially oriented polyester film in the machine direction and the perpendicular direction is preferably 200% or less.

[0064] The Young's modulus and tensile elongation of a biaxially stretched film containing polyester as a primary component can be measured in accordance with JIS K7127, as in the case of a high-stiffness polyester film. A tensile tester STA-1150 manufactured by Orientec Co., Ltd. can be used as the measuring instrument. A rectangular film 15 mm wide and 150 mm long cut from the film can be used as a test piece. The distance between the pair of chucks holding the test piece at the start of measurement is 100 mm, and the tensile speed is 300 mm / min.

[0065] The thickness of the biaxially oriented polyester film is preferably 9 μm or more, more preferably 12 μm or more. Furthermore, the thickness of the biaxially oriented polyester film is preferably 25 μm or less, more preferably 20 μm or less. By making the thickness of the biaxially oriented polyester film 9 μm or more, the biaxially oriented polyester film has sufficient strength. Furthermore, by making the thickness of the biaxially oriented polyester film 25 μm or less, the biaxially oriented polyester film exhibits excellent formability. Therefore, the process of processing the packaging material 30 to produce the bag 10 can be carried out efficiently.

[0066] Preferably, the material constituting the biaxially oriented polyester film has a thermal conductivity equal to or greater than a predetermined value. For example, the thermal conductivity of the material constituting the biaxially oriented polyester film is preferably equal to or greater than 0.05 W / m·K, and more preferably equal to or greater than 0.1 W / m·K. The thermal conductivity of PET is, for example, 0.14 W / m·K. The thermal conductivity of PBT is higher than that of PET, for example, 0.25 W / m·K. By using a material with a thermal conductivity equal to or greater than a predetermined value, the heat resistance of the packaging material 30 can be improved.

[0067] The melting point of the biaxially oriented polyester film is preferably 200° C. or higher, and more preferably 220° C. or higher. By setting the melting point of the biaxially oriented polyester film to 220° C. or higher, it is possible to prevent holes from being formed in the biaxially oriented polyester film and prevent wrinkles from being formed in the biaxially oriented polyester film when the contents contained in the bag 10 produced using the packaging material 30 are heated.

[0068] The biaxially oriented polyester film constituting the other of the first biaxially oriented plastic film 40 and the second biaxially oriented plastic film 50 may be configured to have tearability in the machine direction (MD). In the following description, a biaxially oriented polyester film having tearability in the machine direction (MD) is also referred to as a biaxially oriented straight-cut film. The use of a biaxially oriented straight-cut film can impart tearability in the machine direction (MD) to the packaging material 30. In the bag 10 shown in FIG. 1, the first direction D1 corresponds to the machine direction (MD) of a film such as the biaxially oriented plastic film 40, 50. The second direction D2 corresponds to the transverse direction (TD) of a film such as the biaxially oriented plastic film 40, 50.

[0069] The biaxially stretched straight-cut film will be described below. The tensile strength of a biaxially stretched straight-cut film in the machine direction (MD) is greater than the tensile strength of a biaxially stretched straight-cut film in the transverse direction (TD). The tensile strength of a biaxially stretched straight-cut film in the machine direction (MD) is preferably 1.05 times or more, more preferably 1.10 times or more, and even more preferably 1.2 times or more, of the tensile strength of a biaxially stretched straight-cut film in the transverse direction (TD). The tensile strength of a biaxially stretched straight-cut film in the machine direction (MD) is, for example, 200 MPa or more and 300 MPa or less.

[0070] When the biaxially oriented polyester film constituting the other of the first biaxially oriented plastic film 40 and the second biaxially oriented plastic film 50 contains PET, the PET may contain biomass-derived PET, as in the case of the high-stiffness polyester film described above. In this case, the biaxially oriented polyester film may be composed solely of biomass-derived PET. Alternatively, the biaxially oriented polyester film may be composed of biomass-derived PET and fossil fuel-derived PET. The biomass-derived PET contained in the biaxially oriented polyester film and the biomass content of the biaxially oriented polyester film are the same as in the case of the high-stiffness polyester film described above, and therefore further explanation is omitted.

[0071] In this embodiment, examples of combinations of the first biaxially stretched plastic film 40 and the second biaxially stretched plastic film 50 are as follows. TIFF0007818884000001.tif59170

[0072] (First adhesive layer) The first adhesive layer 45 contains an adhesive for bonding the first biaxially oriented plastic film 40 and the second biaxially oriented plastic film 50 by a dry lamination method. The adhesive constituting the first adhesive layer 45 is produced from an adhesive composition prepared by mixing a first composition containing a base agent and a solvent with a second composition containing a curing agent and a solvent. Specifically, the adhesive contains a cured product produced by reaction of the base agent and the solvent in the adhesive composition.

[0073] An example of an adhesive is polyurethane. Polyurethane is a cured product produced by reacting a polyol as a base agent with an isocyanate compound as a curing agent. Examples of polyurethane include polyether polyurethane and polyester polyurethane. Polyether polyurethane is a cured product produced by reacting a polyether polyol as a base agent with an isocyanate compound as a curing agent. Polyester polyurethane is a cured product produced by reacting a polyester polyol as a base agent with an isocyanate compound as a curing agent.

[0074] As the isocyanate compound, aromatic isocyanate compounds such as tolylene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), and xylylene diisocyanate (XDI), aliphatic isocyanate compounds such as hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI), or adducts or polymers of the above-mentioned various isocyanate compounds can be used.

[0075] The material constituting the first adhesive layer 45 preferably has a higher thermal conductivity than the materials constituting the first biaxially oriented plastic film 40, the second biaxially oriented plastic film 50, and the sealant layer 70. For example, the thermal conductivity of the material constituting the first adhesive layer 45 is preferably 1.0 W / m·K or higher, more preferably 3.0 W / m·K or higher. The thermal conductivity of polyurethane is in the range of 3.0 W / m·K to 5.0 W / m·K, e.g., 5.0 W / m·K. The high thermal conductivity of the material constituting the first adhesive layer 45 facilitates heat diffusion in the planar direction of the packaging material 30 as heat generated in the storage section 17 is transferred from the inner surface 30x of the packaging material 30 to the outer surface 30y of the packaging material 30 when the bag 10 made using the packaging material 30 is heated. This improves the heat dissipation properties of the packaging material 30, thereby suppressing temperature rise in the packaging material 30. This also reduces damage to the packaging material 30 caused by heat when the bag 10 is heated. That is, the heat resistance of the packaging material 30 can be improved.

[0076] The thickness of the first adhesive layer 45 is preferably 2 μm or more, and more preferably 3 μm or more. The thickness of the first adhesive layer 45 is preferably 6 μm or less, and more preferably 5 μm or less. By making the thickness of the first adhesive layer 45 3 μm or more, heat diffusion in the surface direction of the packaging material 30 becomes easier to occur.

[0077] (Second adhesive layer) When the sealant layer 70 is made of a sealant film, the second adhesive layer 55 contains an adhesive for bonding the second biaxially oriented plastic film 50 and the sealant film by dry lamination. An example of the adhesive for the second adhesive layer 55 is polyurethane, as in the case of the first adhesive layer 45. In addition to the configuration, materials, and properties described below, the second adhesive layer 55 can also have the same configuration, materials, and properties as the first adhesive layer 45.

[0078] The material constituting the second adhesive layer 55, like the first adhesive layer 45, preferably has a higher thermal conductivity than the materials constituting the first biaxially oriented plastic film 40, the second biaxially oriented plastic film 50, and the sealant film. For example, the thermal conductivity of the material constituting the second adhesive layer 55 is preferably 1 W / m·K or more, and more preferably 3 W / m·K or more.

[0079] The thickness of the second adhesive layer 55 is preferably 2 μm or more, and more preferably 3 μm or more. The thickness of the second adhesive layer 55 is preferably 6 μm or less, and more preferably 5 μm or less.

[0080] As described above, the isocyanate compounds constituting the curing agent of the adhesive include aromatic isocyanate compounds and aliphatic isocyanate compounds. Among these, aromatic isocyanate compounds leach out components that cannot be used in food applications under high-temperature conditions such as heat sterilization. The second adhesive layer 55 contacts the sealant film. Therefore, if the second adhesive layer 55 contains an aromatic isocyanate compound, components leach out from the aromatic isocyanate compound may adhere to the contents contained in the container 17, which contacts the sealant film.

[0081] In consideration of these issues, a cured product produced by the reaction of a polyol as the main agent with an aliphatic isocyanate compound as the curing agent is preferably used as the adhesive that constitutes the second adhesive layer 55. This makes it possible to prevent components that cannot be used for food applications, which originate from the second adhesive layer 55, from adhering to the contents.

[0082] (sealant layer) Next, the sealant layer 70 will be described. The material constituting the sealant layer 70 can be one or more resins selected from polyethylene, such as low-density polyethylene and linear low-density polyethylene, and polypropylene. The sealant layer 70 may be a single layer or a multilayer. The sealant layer 70 may also be composed of an unstretched sealant film. Note that the term "unstretched" refers not only to a film that is not stretched at all, but also to a film that is slightly stretched due to the tension applied during film formation.

[0083] The sealant film constituting the sealant layer 70 is, for example, a plastic film that has been stretched to an extent necessary for transportation but has not been intentionally stretched. Preferred mechanical properties of the sealant film will be further described. The Young's modulus of the sealant film in at least one direction is preferably 1000 MPa or less, for example, the Young's modulus of the sealant film in the machine direction and perpendicular direction is preferably 1000 MPa or less. The tensile elongation of the sealant film in at least one direction is preferably 300% or more, for example, the tensile elongation of the sealant film in the machine direction and the perpendicular direction is preferably 300% or more.

[0084] The Young's modulus and tensile elongation of the sealant film can be measured in accordance with JIS K7127, as in the case of high-stiffness polyester films. A tensile tester STA-1150 manufactured by Orientec Co., Ltd. can be used as the measuring instrument. A rectangular film 15 mm wide and 150 mm long cut from the film can be used as the test piece. The distance between the pair of chucks holding the test piece at the start of measurement is 100 mm, and the tensile speed is 300 mm / min.

[0085] Bags 10 made from packaging material 30 may be subjected to sterilization treatments such as boiling or retort treatment at high temperatures. The sealant layer 70 preferably has heat resistance that can withstand these high-temperature treatments. Retort treatment is a process in which the contents are filled into bag 10, the bag 10 is sealed, and then the bag 10 is heated under pressure using steam or heated hot water. The temperature for retort treatment is, for example, 120°C or higher. Boiling treatment is a process in which the contents are filled into bag 10, the bag 10 is sealed, and then the bag 10 is heated in a water bath under atmospheric pressure. The temperature for boiling treatment is, for example, 90°C or higher and 100°C or lower.

[0086] The melting point of the material that constitutes sealant layer 70 is preferably 150°C or higher, and more preferably 160°C or higher. Increasing the melting point of sealant layer 70 makes it possible to perform retort processing of bag 10 at a high temperature, thereby shortening the time required for retort processing. Note that the melting point of the material that constitutes sealant layer 70 is lower than the melting point of the resin that constitutes biaxially oriented plastic films 40, 50.

[0087] From the perspective of retort processing, a material primarily composed of propylene can be used to form the sealant layer 70. Here, a material "primarily composed of" propylene refers to a material with a propylene content of 90% by mass or more. Specific examples of materials primarily composed of propylene include polypropylenes such as propylene-ethylene block copolymers, propylene-ethylene random copolymers, and homopolypropylenes, as well as mixtures of polypropylene and polyethylene. Here, "propylene-ethylene block copolymers" refer to materials having the structural formula shown in formula (I) below. Furthermore, "propylene-ethylene random copolymers" refer to materials having the structural formula shown in formula (II) below. Furthermore, "homopolypropylene" refers to materials having the structural formula shown in formula (III) below.

[0088] [ka]

[0089] [ka]

[0090] [ka]

[0091] When a mixture of polypropylene and polyethylene is used as the propylene-based material, the material may have an island-in-a-sea structure, where the polyethylene is discontinuously dispersed within a continuous polypropylene region.

[0092] Considering the boiling treatment, examples of the material constituting the sealant layer 70 include polyethylene, polypropylene, and a combination thereof. Examples of polyethylene include medium-density polyethylene, linear low-density polyethylene, and a combination thereof. For example, it is also possible to use the materials listed above as materials constituting the sealant layer 70 from the viewpoint of retort treatment. The material constituting the sealant layer 70 has a melting point of, for example, 100°C or higher, more preferably 105°C or higher, more preferably 110°C or higher, and even more preferably 115°C or higher. When polyethylene is used as the material constituting the sealant layer 70, a melting point of 100°C or higher is achieved, for example, when the density of polyethylene is 0.920 g / cm. 3 This can be achieved when the above conditions are satisfied. Specific examples of sealant layers for constituting the sealant layer 70 having a melting point of 100°C or higher include TUX-HC manufactured by Mitsui Chemicals Tohcello, L6101 manufactured by Toyobo, and LS700C manufactured by Idemitsu Unitech. Specific examples of sealant layers for constituting the sealant layer 70 having a melting point of 105°C or higher include NB-1 manufactured by Tamapoly. Specific examples of sealant layers for constituting the sealant layer 70 having a melting point of 110°C or higher include LS760C manufactured by Idemitsu Unitech and TUX-HZ manufactured by Mitsui Chemicals Tohcello.

[0093] Preferably, the sealant layer 70 is a single-layer film containing a propylene-ethylene block copolymer. For example, the sealant layer including the sealant layer 70 is a single-layer unstretched film whose main component is a propylene-ethylene block copolymer. By using a propylene-ethylene block copolymer, the impact resistance of the sealant layer can be increased, thereby preventing the bag 10 from breaking due to an impact when dropped. Furthermore, the puncture resistance of the packaging material 30 can be increased.

[0094] A propylene-ethylene block copolymer, for example, contains a sea component made of polypropylene and island components made of an ethylene-propylene copolymer rubber component. The sea component can contribute to improving the blocking resistance, heat resistance, rigidity, seal strength, etc. of the propylene-ethylene block copolymer. The island components can also contribute to improving the impact resistance of the propylene-ethylene block copolymer. Therefore, by adjusting the ratio of the sea component to the island component, the mechanical properties of a sealant layer containing a propylene-ethylene block copolymer can be adjusted.

[0095] In the propylene-ethylene block copolymer, the mass ratio of the sea part made of polypropylene is higher than the mass ratio of the island part made of ethylene-propylene copolymer rubber component. For example, in the propylene-ethylene block copolymer, the mass ratio of the sea part made of polypropylene is at least 51 mass% or more, preferably 60 mass% or more, and more preferably 70 mass% or more.

[0096] The single-layer sealant layer may further contain a second thermoplastic resin in addition to the first thermoplastic resin consisting of a propylene-ethylene block copolymer. Examples of the second thermoplastic resin include α-olefin copolymers and polyethylene. An example of an α-olefin copolymer is linear low-density polyethylene. Examples of polyethylene include low-density polyethylene, medium-density polyethylene, and high-density polyethylene. The second thermoplastic resin may contribute to increasing the impact resistance of the sealant layer.

[0097] Low density polyethylene has a density of 0.910 g / cm 3 or more and 0.925g / cm 3 Medium density polyethylene has a density of 0.926 g / cm 3 or more and 0.940 g / cm 3 High density polyethylene is polyethylene with a density of 0.941 g / cm 3 or more and 0.965g / cm 3 The following polyethylenes are available: Low-density polyethylene is obtained by polymerizing ethylene at a high pressure, for example, of 1000 atmospheres or more and less than 2000 atmospheres; medium-density polyethylene and high-density polyethylene are obtained by polymerizing ethylene at a medium or low pressure, for example, of 1 atmosphere or more and less than 1000 atmospheres.

[0098] It should be noted that medium-density polyethylene and high-density polyethylene may partially contain a copolymer of ethylene and an α-olefin. Even when ethylene is polymerized under medium or low pressure, medium-density or low-density polyethylene can be produced if it contains a copolymer of ethylene and an α-olefin. Such polyethylene is referred to as the linear low-density polyethylene mentioned above. Linear low-density polyethylene is obtained by copolymerizing an α-olefin with a linear polymer obtained by polymerizing ethylene under medium or low pressure to introduce short-chain branches. Examples of α-olefins include 1-butene (C4), 1-hexene (C6), 4-methylpentene (C6), and 1-octene (C8). The density of linear low-density polyethylene is, for example, 0.915 g / cm. 3 or more and 0.945 g / cm 3 The following is the result.

[0099] The α-olefin copolymer constituting the second thermoplastic resin of the propylene-ethylene block copolymer is not limited to the linear low-density polyethylene described above. The α-olefin copolymer refers to a material having the structural formula shown in formula (IV) below.

[0100] [ka] Both R1 and R2 are H (hydrogen atom) or alkyl groups such as CH3 and C2H5. Furthermore, both j and k are integers of 1 or greater. Furthermore, j is greater than k. That is, in the α-olefin copolymer represented by formula (IV), the structure on the left side including R1 is the base. R1 is, for example, H, and R2 is, for example, C2H5.

[0101] In the sealant layer, the mass ratio of the first thermoplastic resin comprising a propylene-ethylene block copolymer is higher than the mass ratio of the second thermoplastic resin containing at least an α-olefin copolymer or polyethylene. For example, in a single sealant layer, the mass ratio of the first thermoplastic resin comprising a propylene-ethylene block copolymer is at least 51 mass% or more, preferably 60 mass% or more, and more preferably 70 mass% or more.

[0102] As described above, the second thermoplastic resin can contribute to increasing the impact resistance of the sealant layer. Therefore, by adjusting the mass ratio of the second thermoplastic resin containing at least an α-olefin copolymer or polyethylene in the single sealant layer, the mechanical properties of the sealant layer can be adjusted.

[0103] The sealant layer 70 may further contain a thermoplastic elastomer. By using a thermoplastic elastomer, the impact resistance and puncture resistance of the sealant layer 70 can be further improved.

[0104] The thermoplastic elastomer is, for example, a hydrogenated styrene-based thermoplastic elastomer. The hydrogenated styrene-based thermoplastic elastomer has a structure consisting of a polymer block A mainly composed of at least one vinyl aromatic compound and a polymer block B mainly composed of at least one hydrogenated conjugated diene compound. The thermoplastic elastomer may also be an ethylene-α-olefin elastomer. The ethylene-α-olefin elastomer is a low-crystalline or amorphous copolymer elastomer, and is a random copolymer of 50 to 90% by mass of ethylene as the main component and an α-olefin as a copolymerization monomer.

[0105] The content of the propylene-ethylene block copolymer in the sealant layer 70 is, for example, 80% by mass or more, and preferably 90% by mass or more.

[0106] Propylene-ethylene block copolymers can be produced by polymerizing the raw materials propylene and ethylene using a catalyst, such as a Ziegler-Natta catalyst or a metallocene catalyst.

[0107] The thickness of the sealant layer 70 is preferably 30 μm or more, and more preferably 40 μm or more. The thickness of the sealant layer 70 is preferably 100 μm or less, and more preferably 80 μm or less.

[0108] In the following, preferred mechanical properties of the sealant film when the sealant layer 70 is made of a single layer sealant film containing a propylene-ethylene block copolymer will be described. The tensile elongation of the sealant film in the machine direction (MD) at 25°C is preferably 600% or more and 1300% or less. The product of the tensile elongation (%) of the sealant film in the machine direction (MD) and the thickness (μm) of the sealant film is preferably 35,000 or more and 80,000 or less. The tensile elongation of the sealant film in the transverse direction (TD) at 25°C is preferably 700% or more and 1400% or less. The product of the tensile elongation (%) of the sealant film in the transverse direction (TD) and the thickness (μm) of the sealant film is preferably 40,000 or more and 85,000 or less. The tensile modulus of the sealant film in the machine direction (MD) at 25°C is preferably 400 MPa or more and 1100 MPa or less. The product of the tensile modulus of the sealant film in the machine direction (MD) (MPa) and the thickness (μm) of the sealant film is preferably 30,000 or more and 55,000 or less. The tensile modulus of the sealant film in the transverse direction (TD) at 25°C is preferably 250 MPa or more and 900 MPa or less. The product of the tensile modulus of the sealant film in the transverse direction (TD) (MPa) and the thickness (μm) of the sealant film is preferably 20,000 or more and 45,000 or more. 1, the first direction D1 corresponds to the machine direction (MD) of the sealant film, and the second direction D2 corresponds to the perpendicular direction (TD) of the sealant film.

[0109] The tensile modulus and tensile elongation can be measured in accordance with JIS K7127. A tensile tester STA-1150 manufactured by Orientec Co., Ltd. can be used as a measuring device. In the bag 10 shown in FIG. 1 , the direction in which the upper portion 11 and the lower portion 12 extend is the machine direction of the film constituting the bag 10, such as a sealant film, and the direction in which the side portion 13 extends is perpendicular to the film constituting the bag 10, such as a sealant film. Although not shown, the bag 10 may be configured so that the direction in which the upper portion 11 and the lower portion 12 extend is perpendicular to the film and the direction in which the side portion 13 extends is the machine direction of the film.

[0110] There are two main types of single-layer sealant films containing propylene-ethylene block copolymers. The first type is a type that has high tensile elongation and impact resistance, such as unstretched polypropylene film ZK500 manufactured by Toray Advanced Film Co., Ltd. The first type of sealant film preferably also has the property of low hot seal strength. This prevents excessive internal pressure in the storage section 17 when the bag 10 is heated, thereby preventing damage to the packaging material 30. The second type is a type with a high tensile modulus, such as unstretched polypropylene film ZK207 manufactured by Toray Advanced Film Co., Ltd. Use of the second type of sealant film can improve tearability when a consumer tears bag 10 along first direction D1 to open bag 10.

[0111] The product of the tensile elongation (%) of the first type sealant film in the machine direction (MD) and the thickness (μm) of the sealant film is preferably 45,000 or more, more preferably 50,000 or more, or may be 55,000 or more, or 60,000 or more. The product of the tensile elongation (%) of the first type sealant film in the transverse direction (TD) and the thickness (μm) of the sealant film is preferably 53,000 or more, more preferably 60,000 or more. When the sealant film has a high tensile elongation, it is possible to prevent the bag 10 from breaking due to an impact when dropped, for example. Furthermore, the product of the tensile modulus (MPa) of the first type sealant film in the machine direction (MD) and the thickness (μm) of the sealant film is preferably not more than 38,000, more preferably not more than 35,000. Furthermore, the product of the tensile modulus (MPa) of the first type sealant film in the transverse direction (TD) and the thickness (μm) of the sealant film is preferably not more than 30,000, more preferably not more than 25,000.

[0112] The product of the tensile modulus (MPa) of the second type sealant film in the machine direction (MD) and the thickness (μm) of the sealant film is preferably 35,000 or more, more preferably 38,000 or more, and even more preferably 45,000 or more. The product of the tensile modulus (MPa) of the second type sealant film in the transverse direction (TD) and the thickness (μm) of the sealant film is preferably 25,000 or more, more preferably 30,000 or more, even more preferably 35,000 or more, and may be 38,000 or more. When the sealant film has a high tensile modulus, the tearability when opening the bag 10 can be improved. Furthermore, the product of the tensile elongation (%) of the second type sealant film in the machine direction (MD) and the thickness (μm) of the sealant film is preferably not more than 55,000, more preferably not more than 50,000. Furthermore, the product of the tensile elongation (%) of the second type sealant film in the transverse direction (TD) and the thickness (μm) of the sealant film is preferably not more than 60,000, more preferably not more than 55,000.

[0113] As will be shown in the examples described later, when the first type of sealant film is used, it is possible to increase the drop strength of a packaging container such as a bag 10 made of the packaging material 30. Therefore, when the packaging material 30 is used in an application requiring drop strength, it is preferable that the packaging material 30 include the first type of sealant film.

[0114] The sealant layer 70 may have easy-peel properties. Easy-peel properties refer to the property that, when a packaging material 30 having a sealant layer 70 is used to form a lid for a container, the lid can be easily peeled from the flange of the container at its underside, i.e., at the sealant layer 70. Easy-peel properties can be achieved, for example, by forming the sealant layer 70 from two or more types of resins, with one resin being incompatible with the other resins. Examples of resins that can achieve easy-peel properties include mixed resins of polyethylene and polypropylene, such as high-density polyethylene.

[0115] 12, the sealant layer 70 may include a first layer 71 located on the second biaxially oriented plastic film 50 side, and a second layer 72 located more inward than the first layer 71 and constituting the inner surface 30x of the packaging material 30. The first layer 71 and second layer 72 of the sealant layer 70 having easy peel properties can be mainly of two types, such as Type A and Type B described below.

[0116] In the A-type sealant layer 70, the first layer 71 is a layer containing polyethylene as a main component, and the second layer 72 is a layer containing a mixed resin of polyethylene and polypropylene. In the second layer 72, the blend ratio of polypropylene is higher than the blend ratio of polyethylene. The mass ratio of polypropylene to polyethylene in the second layer 72 is 6:4 to 8:2.

[0117] When the packaging material 30 having the A-type sealant layer 70 is used in a packaged product for heat sterilization, the density of the polyethylene in the sealant layer 70 is set to 0.940 g / cm 3 It is preferable that the above is set.

[0118] The polypropylene in the second layer 72 of the A-type sealant layer 70 may be, for example, an ethylene-propylene random copolymer.

[0119] In the A-type sealant layer 70, the ratio of the thickness of the first layer 71 to the thickness of the second layer 72 can be set to 5:1 to 10:1.

[0120] In the B-type sealant layer 70, the first layer 71 is a layer containing polypropylene as a main component, and the second layer 72 is a layer containing a mixed resin of polyethylene and polypropylene. In the second layer 72, the blend ratio of polypropylene is higher than the blend ratio of polyethylene. The mass ratio of polypropylene to polyethylene in the second layer 72 is 6:4 to 8:2.

[0121] When the packaging material 30 having the B-type sealant layer 70 is used in a packaged product for heat sterilization, the density of the polyethylene in the sealant layer 70 is set to 0.940 g / cm 3 It is preferable that the above is set.

[0122] The polypropylene in the first layer 71 of the B-type sealant layer 70 may be, for example, an ethylene-propylene block copolymer. The polypropylene in the second layer 72 of the B-type sealant layer 70 may be, for example, an ethylene-propylene random copolymer.

[0123] In the B-type sealant layer 70, the ratio of the thickness of the first layer 71 to the thickness of the second layer 72 can be set to 3:1 to 8:1.

[0124] The sealant layer 70 may be a resin layer provided by an extrusion method or the like on the inner surface side of the second biaxially oriented plastic film 50. In this case, the second adhesive layer 55 described above does not need to be present between the second biaxially oriented plastic film 50 and the sealant layer 70.

[0125] (Other layers) The packaging material 30 may further include a printed layer 32. In the example shown in Figure 2, the printed layer 32 is located between the first biaxially oriented plastic film 40 and the first adhesive layer 45.

[0126] The printed layer 32 is a layer for displaying information about the contents or packaged product, and for adding aesthetic appeal to a packaged product such as the bag 10. The printed layer expresses letters, numbers, symbols, figures, pictures, etc. The printed layer contains a binder resin and a coloring material such as a dye or pigment dispersed in the binder resin. Materials that can be used to form the printed layer include gravure printing ink and flexographic printing ink. A specific example of gravure printing ink is Finart, manufactured by DIC Graphics Corporation.

[0127] Fig. 3 is a cross-sectional view showing a modified example of the layer structure of the packaging material 30. As shown in Fig. 3, the packaging material 30 may include a vapor deposition layer 34 located on the surface of the first biaxially stretched plastic film 40 facing the inner surface 30x. The packaging material 30 may further include a transparent gas barrier coating film 36 located on the surface of the vapor deposition layer 34.

[0128] Fig. 4 is a cross-sectional view showing a modified example of the layer structure of the packaging material 30. As shown in Fig. 4, the vapor deposition layer 34 may be located on the surface of the second biaxially oriented plastic film 50 facing the outer surface 30y. In addition, a gas barrier coating film 36 may be provided on the surface of the vapor deposition layer 34.

[0129] The vapor deposition layer 34 and the gas barrier coating film 36 will be described below.

[0130] The vapor-deposited layer 34 is a layer provided on the packaging material 30 to improve the gas barrier properties of the packaging material 30. Examples of materials that can be used to form the vapor-deposited layer 34 include metals such as aluminum, metal oxides such as aluminum oxide, and inorganic oxides such as silicon oxide.

[0131] The vapor deposition layer 34 functions as a layer with gas barrier properties that prevent the permeation of oxygen gas, water vapor, and the like. Two or more vapor deposition layers 34 may be provided. When two or more vapor deposition layers 34 are provided, the layers may have the same composition or different compositions. Examples of methods for forming the vapor deposition layer 34 include physical vapor deposition (PVD) methods such as vacuum deposition, sputtering, and ion plating, and chemical vapor deposition (CVD) methods such as plasma-enhanced chemical vapor deposition, thermal chemical vapor deposition, and photochemical vapor deposition. Specifically, the vapor deposition layer can be formed on a film-forming roller using a roller-type vapor deposition film-forming device.

[0132] The vapor deposition layer 34 may be a transparent vapor deposition layer formed of a transparent inorganic material such as aluminum oxide (aluminum oxide) or silicon oxide. In particular, when the printing layer 32 is provided on the inner surface 30x side of the vapor deposition layer 34, the vapor deposition layer 34 is configured as a transparent vapor deposition layer. It is preferable to use an amorphous thin film of aluminum oxide as the transparent vapor deposition layer. Specifically, the transparent vapor deposition layer is formed of a material having the formula AlO X(wherein X is a number in the range of 0.5 to 1.5). The transparent vapor deposition layer can be an amorphous thin film of aluminum oxide in which the value of X decreases in the depth direction from the film surface toward the inner surface. The amorphous thin film of aluminum oxide can be an amorphous thin film of aluminum oxide represented by the formula AlO X (wherein X is a number in the range of 0.5 to 1.5), and it is preferable that the value of X increases in the depth direction from the surface of the thin film toward the inner surface. In the above formula, the value of X can basically be 0.5 or more, but if X is less than 1.0, severe coloring occurs and transparency is poor, so it is preferable to use X = 1.0 or more. Furthermore, since X = 1.5 is a state in which Al and oxygen are completely oxidized, the upper limit of X = 1.5 can be used. In addition, if the value of X in the above formula is 0, it is a completely inorganic element (pure substance) and is not transparent.

[0133] The rate of decrease in the value of X can be confirmed by performing elemental analysis of the transparent vapor-deposited layer using a surface analyzer such as an X-ray photoelectron spectroscopy (XPS) or a secondary ion mass spectroscopy (SIMS), using a method of analysis such as ion etching in the depth direction.

[0134] <First Preferred Form of Transparent Vapor Deposition Layer> A first preferred embodiment of the transparent vapor-deposited layer will be described below. The transparent vapor-deposited layer may be a layer made of a mixture of inorganic compounds containing a covalent bond between an aluminum atom and a carbon atom. In this case, the transparent vapor-deposited layer exhibits the presence of a covalent bond between an aluminum atom and a carbon atom in a peak measured by ion etching in the depth direction using an X-ray photoelectron spectrometer (measurement conditions: X-ray source AlKα, X-ray output 120 W), and may also have transparency and gas barrier properties that prevent the permeation of oxygen, water vapor, etc.

[0135] A covalent bond between a metal atom and a carbon atom may be formed at the interface between the transparent vapor deposition layer and the biaxially stretched plastic film. For example, if the transparent vapor deposition layer contains aluminum oxide, a covalent bond between an aluminum atom and a carbon atom may be formed at the interface between the biaxially stretched plastic film and the transparent vapor deposition layer. The covalent bond can be detected by measurement using X-ray photoelectron spectroscopy (hereinafter abbreviated as "XPS measurement").

[0136] Furthermore, in the transparent vapor-deposited layer, the proportion of covalent bonds between aluminum atoms and carbon atoms is preferably within the range of 0.3% to 30% of all bonds including carbon atoms observed when the interface between the transparent vapor-deposited layer and the biaxially stretched plastic film is measured by XPS, which strengthens the adhesion between the transparent vapor-deposited layer and the biaxially stretched plastic film, and provides a vapor-deposited film with excellent transparency and well-balanced gas barrier properties.

[0137] If the proportion of covalent bonds between aluminum atoms and carbon atoms is less than 0.3%, the improvement in adhesion of the transparent vapor-deposited layer is insufficient, making it difficult to stably maintain the barrier properties.

[0138] Furthermore, it is preferable that the AL (aluminum) / O (oxygen) ratio of the transparent vapor deposition layer, which is primarily composed of aluminum oxide, is 1.0 or less within a range of 3 nm from the interface between the biaxially oriented plastic film and the transparent vapor deposition layer toward the surface of the transparent vapor deposition layer on the side opposite the biaxially oriented plastic film. If the AL / O ratio exceeds 1.0 in the range from the interface between the transparent vapor deposition layer and the biaxially oriented plastic film toward the surface of the transparent vapor deposition layer opposite the biaxially oriented plastic film, the adhesion between the biaxially oriented plastic film and the transparent vapor deposition layer will be insufficient, and the proportion of aluminum will increase, reducing the transparency of the transparent vapor deposition layer.

[0139] The thickness of the transparent vapor deposition layer is, for example, 20 Å or more and 200 Å or less, preferably 30 Å or more and 150 Å or more. A thickness less than 30 Å may result in insufficient gas barrier properties. On the other hand, a thickness greater than 150 Å may result in the packaging material 30 being unable to maintain its gas barrier properties. While the reason for this is unclear, a thickness greater than 150 Å is thought to reduce the flexibility of the packaging material 30, resulting in cracks or pinholes forming in the transparent vapor deposition layer when the packaging material 30 is used in a bag 10, resulting in reduced gas barrier properties. The thickness of the transparent vapor deposition layer is preferably 40 Å or more and 130 Å or less, more preferably 50 Å or more and 120 Å or less. The thickness of the transparent vapor deposition layer can be measured, for example, by the fundamental parameter method using an X-ray fluorescence analyzer (product name: RIX2000, manufactured by Rigaku Corporation). The thickness of the transparent vapor deposition layer can be changed by, for example, changing the deposition rate of the transparent vapor deposition layer or the vapor deposition rate.

[0140] The surface of the biaxially stretched plastic film may be subjected to a pretreatment such as corona discharge treatment, flame treatment, or plasma treatment. When the pretreatment is plasma treatment, plasma is supplied to the surface of the biaxially stretched plastic film using a pretreatment device in a reduced pressure environment of 0.1 Pa to 100 Pa. Plasma can be generated by using an inert gas such as argon alone or a mixture of oxygen, nitrogen, carbon dioxide, or one or more of these gases as a plasma raw material gas and exciting the plasma raw material gas with a potential difference such as a high-frequency voltage.

[0141] Pretreatment allows plasma to be confined near the surface of the biaxially stretched plastic film. This changes the surface shape, chemical bonding state, and functional groups of the biaxially stretched plastic film, thereby changing the chemical properties of the surface of the biaxially stretched plastic film. This makes it possible to improve the adhesion between the biaxially stretched plastic film and the transparent vapor deposition layer.

[0142] <Second Preferred Form of Transparent Vapor Deposition Layer> Next, a second preferred embodiment of the transparent vapor-deposited layer will be described. In the present application, the transparent vapor-deposited layer may satisfy both the first preferred embodiment described above and the second preferred embodiment described below, or may satisfy only one of the embodiments. In addition, it is possible that the transparent vapor-deposited layer of the present application does not satisfy either the first preferred embodiment described above or the second preferred embodiment described below.

[0143] The transparent vapor-deposited layer may have a transition region that determines the adhesive strength between the substrate, such as a biaxially stretched plastic film, and the transparent vapor-deposited layer, such as an aluminum oxide vapor-deposited film. When the transparent vapor-deposited layer is an aluminum oxide vapor-deposited film, the transition region contains a bonding structure (Al2O4H) that transforms into aluminum hydroxide, as detected by etching the aluminum oxide vapor-deposited film using time-of-flight secondary ion mass spectrometry (TOF-SIMS). The transformation rate of the transition region, defined as the ratio of the transformed transition region determined using TOF-SIMS to the aluminum oxide vapor-deposited film determined by etching using TOF-SIMS, is preferably 45% or less. This embodiment is based on the finding that specifying the transformation rate of the transition region allows for the identification of a packaging material 30 with barrier properties and improved adhesive strength between the biaxially stretched plastic film and the aluminum oxide vapor-deposited film.

[0144] The transformation rate in the transition region will be explained in detail. First, the outermost surface of the aluminum oxide vapor-deposited film is etched with Cs using a time-of-flight secondary ion mass spectrometer, and the elemental bonding at the interface between the aluminum oxide vapor-deposited film and the biaxially stretched plastic film and the elemental bonding in the vapor-deposited film are measured. Next, actual measurement graphs of the measured elements and elemental bonding are obtained, as shown in Figure 13.

[0145] To minimize the transition region of the interface between the biaxially stretched plastic film and the deposited film, which is formed by aluminum hydroxide in the aluminum oxide deposited film, we focused on AL2O4H. 1) The position where the intensity H0 of the graph for element C6 is half (the position where the intensity becomes H1 in Figure 13) is identified as the interface between the biaxially stretched plastic film and the aluminum oxide deposited film (the position where the horizontal axis (cycle) is T1 in Figure 13). The region from the interface to the surface of the aluminum oxide deposited film (the position where the horizontal axis (cycle) is T0 in Figure 13) is identified as the aluminum oxide deposited film. 2) Next, we found the peak in the graph representing the elemental bond AL2O4H (the position where the horizontal axis (cycle) is T2 in Figure 13), and identified the region from that peak to the interface as the transition region. 3) Next, we calculated the conversion rate to aluminum hydroxide in the transition region by multiplying (the transition region from the peak of the elemental bond AL2O4H to the interface / aluminum oxide deposited film) by 100 (%). In the example shown in FIG. 13, the transformation rate is (W2 / W1)×100(%).

[0146] In forming an aluminum oxide vapor-deposited film, it is preferable to perform plasma pretreatment on the surface of the biaxially stretched plastic film before the aluminum oxide vapor deposition step in order to achieve a preferred conversion rate in the transition region of the aluminum oxide vapor-deposited film. In the plasma pretreatment, the mixture ratio of oxygen gas to argon or helium supplied as plasma gas is 5:1, preferably 2:1. A mixture ratio of 5:1 increases the energy required to form the vapor-deposited aluminum film on the surface of the biaxially stretched plastic film, and a mixture ratio of 2:1 further increases the formation of aluminum hydroxide near the interface with the substrate, i.e., the conversion rate in the transition region decreases.

[0147] As a vapor deposition method for forming the vapor-deposited film, various vapor deposition methods can be applied from among physical vapor deposition and chemical vapor deposition. As a physical vapor deposition method, a method can be selected from the group consisting of vapor deposition, sputtering, ion plating, ion beam assisted deposition, and cluster ion beam deposition. As a chemical vapor deposition method, a method can be selected from the group consisting of plasma CVD, plasma polymerization, thermal CVD, and catalytic reaction CVD. In this embodiment, a physical vapor deposition method is preferred.

[0148] The thickness of the aluminum oxide vapor-deposited film formed as described above is preferably 3 nm or more and 50 nm or less, and more preferably 8 nm or more and 30 nm or less. Within this range, the barrier properties are easily maintained.

[0149] [Gas barrier coating film] The gas barrier coating film 36 is a compound represented by the general formula R 1 n M(OR 2 ) m (wherein, R 1 , R 2 represents an organic group having 1 to 8 carbon atoms, M represents a metal atom, n represents an integer of 0 or more, m represents an integer of 1 or more, and n + m represents the valence of M. The gas barrier coating film 36 is obtained from a transparent gas barrier composition containing at least one alkoxide represented by the formula (I) and the above-mentioned polyvinyl alcohol resin and / or ethylene-vinyl alcohol copolymer, and further polycondensed by a sol-gel method in the presence of a sol-gel catalyst, acid, water, and an organic solvent. It is preferable that the gas barrier coating film 36 is transparent.

[0150] The general formula R 1 n M(OR 2 ) mAs the alkoxide represented by the formula (I), at least one of a partial hydrolyzate of an alkoxide and a condensate of the hydrolysis of an alkoxide can be used. In addition, the partial hydrolyzate of the alkoxide does not necessarily have to have all of the alkoxy groups hydrolyzed, and may be one in which one or more alkoxy groups are hydrolyzed, or a mixture thereof. As the condensate of the hydrolysis of an alkoxide, a dimer or higher of the partially hydrolyzed alkoxide, specifically a dimer to hexamer, is used.

[0151] The general formula R 1 n M(OR 2 ) m In the alkoxide represented by the formula (I), silicon, zirconium, titanium, aluminum, and the like can be used as the metal atom represented by M. Preferred metals include silicon and titanium. In the present embodiment, the alkoxide can be used alone or as a mixture of two or more alkoxides of different metal atoms in the same solution.

[0152] In addition, the above general formula R 1 n M(OR 2 ) m In the alkoxide represented by the formula 1 Specific examples of the organic group represented by the general formula R include alkyl groups such as methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl, t-butyl, n-hexyl, n-octyl, and the like. 1 n M(OR 2 ) m In the alkoxide represented by the formula 2 Specific examples of the organic group represented by the formula (I) include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, a sec-butyl group, etc. These alkyl groups may be the same or different in the same molecule.

[0153] When preparing the transparent gas barrier composition, for example, a silane coupling agent may be added. As the silane coupling agent, a known organoalkoxysilane containing an organic reactive group can be used. In particular, an organoalkoxysilane having an epoxy group is preferably used, and specifically, for example, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, or β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane can be used. The above-mentioned silane coupling agents may be used alone or in combination of two or more.

[0154] The oxygen permeability and water vapor permeability of the packaging material 30 having the vapor deposition layer 34 are preferably 2 or less (cc / m 2 ·day · atm) and less than 2 (g / m 2 ·day). Oxygen permeability is measured in accordance with JIS K7126 (isobaric method) using an oxygen barrier measuring device, OXTRAN, manufactured by Mocon, USA, at 23°C and 90% RH. Water vapor permeability is measured in accordance with JIS K7129 (Method B) using a water vapor barrier measuring device, PERMATRAN, manufactured by Mocon, USA, at 40°C and 90% RH.

[0155] Packaging material manufacturing method Next, an example of a method for producing the packaging material 30 will be described.

[0156] First, prepare the above-mentioned first biaxially stretched plastic film 40 and second biaxially stretched plastic film 50. The first biaxially stretched plastic film 40 or the second biaxially stretched plastic film 50 is provided with a printed layer 32, a vapor deposition layer 34, a gas barrier coating film 36, etc., as needed.

[0157] Next, the first biaxially oriented plastic film 40 and the second biaxially oriented plastic film 50 are laminated together via the first adhesive layer 45 by dry lamination. Thereafter, the laminate including the first biaxially oriented plastic film 40 and the second biaxially oriented plastic film 50 is laminated together with the sealant layer 70 via the second adhesive layer 55 by dry lamination. In this way, a packaging material 30 including the first biaxially oriented plastic film 40, the second biaxially oriented plastic film 50, and the sealant layer 70 can be obtained.

[0158] Alternatively, the packaging material 30 may be produced by first laminating the second biaxially oriented plastic film 50 and the sealant layer 70 via the second adhesive layer 55 using a dry lamination method, and then laminating the first biaxially oriented plastic film 40 and a laminate including the second biaxially oriented plastic film 50 and the sealant layer 70 via the first adhesive layer 45 using a dry lamination method.

[0159] In the dry lamination method, an adhesive composition is first applied to one of the two films to be laminated. The applied adhesive composition is then dried to volatilize the solvent. The two films are then laminated together via the dried adhesive composition. The two laminated films are then rolled up and aged, for example, at 20°C or higher for 24 hours or more.

[0160] Bag manufacturing method Next, a method for manufacturing bag 10 using the above-mentioned packaging material 30 will be described. First, front film 14 and back film 15 made of packaging material 30 are prepared. Next, the inner surfaces of each film are heat-sealed to form seals such as bottom seal 12a and side seal 13a. The films joined together by heat sealing are then cut into an appropriate shape to obtain bag 10 shown in FIG. 1.

[0161] Next, the contents 18 are filled into the bag 10 through the opening 11b of the top 11. Specifically, as shown in FIG. 14, the pair of side seal portions 13a of the bag 10, which are closest to the top 11, are gripped by a pair of zipper portions 105. Furthermore, as shown by arrow P in FIG. 14, the zipper portions 105 are moved in a direction that narrows the gap between the pair of zipper portions 105 in the width direction of the bag 10. This causes the front film 14 and the back film 15 to deform so as to form the opening 11b in the top 11. At this time, as shown in FIG. 14, suction portions 106 may be attached to the outer surfaces of the front film 14 and the back film 15, and the suction portions 106 may be moved in the direction of arrow Q. This makes it easier to form the opening 11b. Next, the contents 18 are filled into the bag 10 through the opening 11b. The top 11 is then heat-sealed to form the top seal portion 11a. In this manner, a bag 10 containing and sealed with the contents 18 can be obtained.

[0162] Contents 18 are, for example, cooked foods containing water, such as curry, stew, soup, etc. Contents 18 may also contain ingredients with a high oil content, such as meat, fish, and seasonings for those. In addition to food, items that can be heated in a hot water bath or the like can also be placed in bag 10 as contents. Contents that do not require heating may also be placed in bag 10.

[0163] In the present embodiment, a high-stiffness polyester film is used as the first biaxially oriented plastic film 40 or the second biaxially oriented plastic film 50 of the packaging material 30 constituting the bag 10. This allows the packaging material 30 and the bag 10 to have excellent puncture strength. This makes it possible to prevent the bag 10 from being torn when it comes into contact with a sharp object having a pointed tip. The puncture strength of the packaging material 30 is preferably 14.0 N or more, more preferably 15.0 N or more, more preferably 16.0 N or more, more preferably 17.0 N or more, more preferably 18.0 N or more, and even more preferably 19.0 N or more. A method for measuring the puncture strength will be described in the Examples below.

[0164] Furthermore, in this embodiment, the second biaxially oriented plastic film 50 contains polyester as a main component. Therefore, compared to when the second biaxially oriented plastic film 50 is a nylon film, the occurrence of coloring of the packaging material 30 due to the contents can be suppressed. This allows the appearance of the packaged product made from the packaging material 30 to be maintained in a good condition.

[0165] Furthermore, in this embodiment, the use of a high-stiffness polyester film as the first biaxially oriented plastic film 40 or the second biaxially oriented plastic film 50 facilitates increasing the rigidity of the packaging material 30. For example, the packaging material 30 has a loop stiffness of 0.100 N or greater in at least one direction. For example, the loop stiffness of the packaging material 30 in the machine direction (MD) is 0.100 N or greater. When the packaging material 30 is rigid, the opening 11b is easily formed in the upper portion 11 when the chuck portion 105 is moved, as shown in FIG. 14 . For example, the front and back films 14 and 15 are easily deformed to have a curved shape that is convex toward the outer surface. This facilitates ensuring the opening width K of the opening 11b. Furthermore, when the packaging material 30 constituting the front and back films 14 and 15 is rigid, the front and back films 14 and 15 are less likely to wrinkle. This facilitates the suction portion 106 to suction the outer surfaces of the front and back films 14 and 15. This can also contribute to ensuring the opening width K of the opening 11b.

[0166] On the other hand, if the loop stiffness of the packaging material 30 is too high, the packaging material 30 may be more susceptible to damage such as tearing when a packaged product made from the packaging material 30 is dropped. In this embodiment, the packaging material 30 is configured so that the loop stiffness of the packaging material 30 in at least one direction is less than 0.150 N. In other words, the packaging material 30 is configured to have appropriate flexibility. This makes it possible to prevent damage such as tearing of the packaging material 30 when a packaged product made from the packaging material 30 is dropped.

[0167] As shown in the examples described below, one method for making the loop stiffness of the packaging material 30 less than 0.150 N in at least one direction is to use a first type of sealant film that has high tensile elongation and impact resistance, such as the unstretched polypropylene film ZK500 described above.

[0168] How to open the bag Next, a method for opening the bag 10 will be described. Here, a case where a consumer opens the bag 10 by tearing the bag 10 along the first direction D1 will be described. In this embodiment, as described above, the first biaxially oriented plastic film 40 or the second biaxially oriented plastic film 50 of the packaging material 30 is Biaxial stretching A straight-cut film may also be used. In this case, it is possible to prevent the tearing direction from deviating from the first direction D1 when the consumer tears open the bag 10. This allows the consumer to easily tear the bag 10. Note that, in order to improve the tearability of the bag 10, it is preferable to use the second type of sealant film described above, which has a high tensile modulus.

[0169] It should be noted that various modifications can be made to the above-described embodiment. Below, modifications will be described with reference to the drawings as necessary. In the following description and the drawings used in the following description, parts that can be configured similarly to the above-described embodiment will be designated by the same reference numerals as those used for the corresponding parts in the above-described embodiment, and duplicated explanations will be omitted. Furthermore, if it is clear that the effects obtained in the above-described embodiment can also be obtained in the modified embodiment, the explanations thereof may be omitted.

[0170] (Variations of the bag) Figure 15 is a diagram showing another example of bag 10 provided with packaging material 30. Bag 10 shown in Figure 15 differs only in that it further includes a lower film 16, and other configurations are substantially the same as bag 10 shown in Figure 1. In bag 10 shown in Figure 15, the same parts as bag 10 shown in Figure 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

[0171] The bag 10 shown in Figure 15 is a gusset-type bag configured to be self-standing. In addition to the components of the bag 10 shown in Figure 1, the bag 10 includes a lower film 16 that configures the lower portion 12. The lower film 16 is folded back at a folded-back portion 16f and disposed between the front film 14 and the back film 15. In this case, the sealed portion includes a lower sealed portion 12a that extends across the lower portion 12. The lower sealed portion 12a includes a sealed portion configured by joining the inner surfaces of the front film 14 and the lower film 16, and a sealed portion configured by joining the inner surfaces of the back film 15 and the lower film 16.

[0172] Bag manufacturing method A method for manufacturing the bag 10 shown in Figure 15 will be described. First, a front film 14 and a back film 15 made of packaging material 30 are prepared. A folded-over bottom film 16 is inserted between the front film 14 and the back film 15. Next, the inner surfaces of the films are heat-sealed to form seals such as a bottom seal 12a and a side seal 13a. The films joined together by heat sealing are then cut into an appropriate shape to obtain the bag 10 shown in Figure 15.

[0173] (Variations of the bag) Figure 16 is a diagram showing another example of bag 10 provided with packaging material 30. Bag 10 shown in Figure 16 differs only in that it further includes a steam release mechanism 20, and other configurations are substantially the same as bag 10 shown in Figure 15. In bag 10 shown in Figure 16, the same parts as bag 10 shown in Figure 15 are designated by the same reference numerals, and detailed description thereof will be omitted.

[0174] 16, bag 10 is provided with a steam release mechanism 20 for releasing steam generated when the contents stored in storage section 17 are heated to the outside. Steam release mechanism 20 is configured to communicate between the inside and outside of bag 10 to release steam when the steam pressure reaches or exceeds a predetermined value, and to prevent steam from escaping from places other than steam release mechanism 20.

[0175] When bag 10 equipped with steam release mechanism 20 is heated in a microwave oven or the like, the pressure inside bag 10 may not rise to a level that allows steam to escape to the outside through steam release mechanism 20. In other words, depending on how bag 10 is used, there may be a low probability that steam release mechanism 20 will perform its function of releasing steam to the outside. Even in this case, providing bag 10 with steam release mechanism 20 can further reduce the probability that steam will escape from a location other than steam release mechanism 20 or that bag 10 will burst.

[0176] In the example shown in FIG. 16 , the steam release mechanism 20 has a steam release seal portion 20a that protrudes from the side seal portion 13a toward the inside of the bag 10, and a non-sealed portion 20b that is isolated from the storage portion 17 by the steam release seal portion 20a. The non-sealed portion 20b is in communication with the outside of the bag 10. When the pressure in the storage portion 17 increases due to heating in a microwave oven or the like, the steam release seal portion 20a peels off. Steam in the storage portion 17 can escape to the outside of the bag 10 through the peeled portion of the steam release seal portion 20a and the non-sealed portion 20b. At this time, the heat resistance of the packaging material 30 makes it possible to prevent holes from being formed in the packaging material 30 or the formation of wrinkles in the packaging material 30 when heated.

[0177] The configuration of the steam release mechanism 20 is not limited to the configuration shown in Fig. 16. The configuration of the steam release mechanism 20 is arbitrary as long as it can communicate between the storage section 17 and the outside of the bag 10 when the steam pressure reaches or exceeds a predetermined value.

[0178] 17, the surface film 14 may include a joint portion 14a in which the inner surfaces of the surface films 14 are partially overlapped. The joint portion 14a may be formed, for example, by folding back a single surface film 14 at a fold-back portion 14f to form a pleat. Alternatively, the joint portion 14a may be formed by overlapping portions of two surface films 14.

[0179] The joint portion 14a has a joint seal portion 14b extending from one side seal portion 13a to the other side seal portion 13a. In this case, the steam release mechanism 20 has, for example, a steam release seal portion 20a protruding from the joint seal portion 14b toward the storage portion 17, a non-sealed portion 20b surrounded by the steam release seal portion 20a and the joint seal portion 14b, and a cut 20c formed in the surface film 14 in the non-sealed portion 20b. As shown in Fig. 17, of the multiple non-sealed portions 14c located in the joint portion 14a between the side portion 13 and the steam release mechanism 20, a cut 14d may also be formed in the surface film 14 in the closest non-sealed portion 14c of the steam release mechanism 20.

[0180] In this modification, when the pressure in storage section 17 increases, steam release sealed section 20a peels off, connecting storage section 17 and non-sealed section 20b. Steam flows from storage section 17 to non-sealed section 20b through the peeled portion of steam release sealed section 20a and escapes to the outside of bag 10 through slit 20c.

[0181] The bag 10 shown in FIG. 17 is placed in a microwave oven so that a wide area of ​​the back surface film 15 is in contact with the turntable or underside (flat table) of the microwave oven. Therefore, the contents are more easily heated uniformly than with the freestanding bag 10 shown in FIG. 16. Furthermore, because the area of ​​the portion of the bag 10 in contact with the microwave oven is large, the liquid level of the contents is less likely to change even if the bag 10 is softened by heating. Therefore, during the heating process using a microwave oven, the contents are less likely to adhere to the inner surface of the front film 14 or back film 15 above the liquid level of the contents. This prevents the contents adhering to the inner surface of the front film 14 or back film 15 from being overheated, resulting in the formation of holes in the front film 14 or back film 15.

[0182] 18A and 18B are a longitudinal cross-sectional view and a plan view showing a lidded container 110, which is an example of an application of the packaging material 30. The lidded container 110 includes a container body 112 fabricated by sheet molding such as drawing or injection molding, and a lid member 114 joined to the container body 112. The container body 112 has a bottom surface 112a, a side surface 112b, and a flange portion 113 extending horizontally outward from the upper end of the side surface 112b. The lid member 114 is joined to the upper surface of the flange portion 113 of the container body 112 via a seal portion 116. The lid member 114 may include the above-described packaging material 30 having at least one high-stiffness polyester film. Using the above-described packaging material 30 to form the lid member 114 can provide the lid member 114 with excellent puncture resistance. This can prevent the lid member 114 from being torn when it comes into contact with a sharp object. Furthermore, if the lidded container 110 is dropped, it is possible to prevent the lidded container 110 from being damaged and the contents from leaking out.

[0183] The sealant layer 70 of the packaging material 30 constituting the lid member 114 may have easy-peel properties. That is, the sealant layer 70 of the packaging material 30 constituting the lid member 114 may have a first layer 71 containing polyethylene or polypropylene as a main component, and a second layer 72 containing a mixed resin of polyethylene and polypropylene and constituting the inner surface 30x.

[0184] In this application, products for packaging items, such as the bag 10 and the lidded container 110, are also referred to as packaging products. [Example]

[0185] Next, the present invention will be explained in more detail with reference to examples. However, the present invention is not limited to the following examples as long as it does not depart from the gist of the present invention.

[0186] The packaging material 30 of the present invention was evaluated for puncture strength, loop stiffness, and drop strength using Examples A1 to A3, Comparative Examples 1 to 3, Examples B1 to B3, and Examples C1 to C3.

[0187] (Example A1) A high-stiffness polyester film made of PET (hereinafter also referred to as high-stiffness PET film) having a loop stiffness of 0.0017 N or more was prepared as the first biaxially stretched plastic film 40. Subsequently, a printed layer having a thickness of 1 μm was formed on the surface of the high-stiffness PET film. Specifically, XP-55 manufactured by Toray Industries, Inc. was used as the high-stiffness PET film. The thickness of the high-stiffness PET film was 16 μm. The measured loop stiffness of the high-stiffness PET film was 0.0021 N in both the machine direction and the perpendicular direction. The Young's modulus of the high-stiffness PET film in the machine direction was 4.8 GPa, and the Young's modulus of the high-stiffness PET film in the perpendicular direction was 4.7 GPa. The tensile strength of the high-stiffness PET film in the machine direction was 292 MPa, and the tensile strength of the high-stiffness PET film in the perpendicular direction was 257 MPa. The tensile elongation of the high-stiffness PET film in the machine direction was 107%, and the tensile elongation of the high-stiffness PET film in the perpendicular direction was 102%. In this case, the tensile strength of the high-stiffness PET film in the machine direction divided by the tensile elongation was 2.73 [MPa / %], and the tensile strength of the high-stiffness PET film in the perpendicular direction divided by the tensile elongation was 2.52 [MPa / %]. The heat shrinkage of the high-stiffness PET film in both the machine direction and the perpendicular direction was 0.4%.

[0188] Also, a biaxially stretched PET film with a thickness of 12 μm was prepared as the second biaxially stretched plastic film 50. The biaxially stretched PET film used had approximately the same tensile strength in the machine direction (MD) and the transverse direction (TD).

[0189] Furthermore, an unstretched polypropylene film ZK500 manufactured by Toray Advanced Film Co., Ltd. was prepared as the sealant layer 70. ZK500 contains the above-mentioned propylene-ethylene block copolymer. The thickness of the sealant layer 70 was 60 μm.

[0190] ZK500 has a higher tensile elongation than general unstretched polypropylene films. Specifically, the tensile elongation of ZK500 in the machine direction (MD) is 1180% when the thickness is 50 μm and 1100% when the thickness is 60 μm. The tensile elongation of ZK500 in the transverse direction (TD) is 1240% when the thickness is 50 μm and 1150% when the thickness is 60 μm. Therefore, the product of the tensile elongation (%) of ZK500 in the machine direction and the thickness (μm) is 59,000 when the thickness is 50 μm and 66,000 when the thickness is 60 μm. The product of the tensile elongation (%) of ZK500 in the transverse direction and the thickness (μm) is 62,000 when the thickness is 50 μm and 69,000 when the thickness is 60 μm.

[0191] Furthermore, ZK500 has a lower tensile modulus than general unstretched polypropylene films. Specifically, the tensile modulus of ZK500 in the machine direction (MD) is 640 MPa when the thickness is 50 μm and 550 MPa when the thickness is 60 μm. The tensile modulus of ZK500 in the transverse direction (TD) is 480 MPa when the thickness is 50 μm and 400 MPa when the thickness is 60 μm. Therefore, the product of the tensile modulus (MPa) of ZK500 in the machine direction and the thickness (μm) is 32,000 when the thickness is 50 μm and 33,000 when the thickness is 60 μm. The product of the tensile modulus (MPa) of ZK500 in the transverse direction and the thickness (μm) is 24,000 when the thickness is 50 μm and 35,000 when the thickness is 60 μm.

[0192] Next, the first biaxially oriented plastic film 40, the second biaxially oriented plastic film 50, and the sealant layer 70 were laminated in this order by dry lamination to produce the packaging material 30. The printed layer was laminated so that it faced the surface of the second biaxially oriented plastic film 50. A two-component polyurethane adhesive (main agent: RU-40, curing agent: H-4) manufactured by Rock Paint Co., Ltd. was used for the first adhesive layer 45 and the second adhesive layer 55. The main agent RU-40 is a polyester polyol. The thickness of the first adhesive layer 45 and the second adhesive layer 55 was 3 μm. The overall thickness of the packaging material 30 was 95 μm.

[0193] [Evaluation of puncture resistance] Next, the puncture strength of the packaging material 30 was measured in accordance with JIS Z1707 7.4. A Tensilon universal testing machine RTC-1310 manufactured by A&D was used as the measuring instrument. Specifically, as shown in FIG. 19 , a semicircular needle 90 with a diameter of 1.0 mm and a tip radius of 0.5 mm was pierced from the outer surface 30y side of a fixed test piece of the packaging material 30 at a speed of 50 mm / min (50 mm per minute), and the maximum stress until the needle 90 penetrated the packaging material 30 was measured. The maximum stress was measured for five or more test pieces, and the average value was used as the puncture strength of the packaging material 30. The measurement was performed in an environment of 23°C and 50% relative humidity. The resulting puncture strength was 16.7 N.

[0194] [Evaluation of loop stiffness] The loop stiffness of the packaging material 30 was also measured in the machine direction and perpendicular direction. The measuring device used was a No. 581 Loop Stiffness Tester (registered trademark) LOOP STIFFNESS TESTER DA type manufactured by Toyo Seiki Seisakusho. The measurement was performed in an environment with a temperature of 23°C and a relative humidity of 50%. As a result, the loop stiffness of the packaging material 30 in the machine direction was 0.134 N, and the loop stiffness in the perpendicular direction was 0.108 N.

[0195] [Evaluation of drop strength] Next, bags 10 were fabricated using the packaging material 30 as the surface film 14, back film 15, and bottom film 16, and the drop strength of the bags 10 was evaluated. Specifically, the bag 10 shown in FIG. 15 was first fabricated using the packaging material 30. The height S1 of the bag 10 was 160 mm, and the width S2 was 147 mm. The height S3 of the folded-back bottom film 16, i.e., the height from the bottom end of the bag 10 to the folded-back portion 16f, was 46 mm. The width S4 of the side seal portion 13a was 7.0 mm. Next, 200 g of water was filled into the bag 10 through the opening 11b of the top portion 11. The top portion 11 was then heat-sealed to form the top seal portion 11a. The width S5 of the top seal portion 11a was 10.0 mm. In this manner, multiple bags 10 shown in FIG. 15 containing 200 g of water were fabricated.

[0196] In the process of producing bag 10, a heat sealer TP-701-A manufactured by Tester Sangyo Co., Ltd. was used as the heat sealing device for forming the seals such as top seal 11a, bottom seal 12a, and side seal 13a. The heat sealing conditions were as follows: Heat sealing temperature: 220℃ Heat sealing time: 1.0 seconds Heat sealing pressure: 0.1 MPa

[0197] Next, the bag 10 containing the water was subjected to a heat sterilization treatment. Specifically, a spray-type retort treatment was performed on the bag 10. The retort temperature was 121°C, and the retort time was 30 minutes.

[0198] Next, some of the plurality of bags 10 after the heat sterilization treatment were stored for one week in an environment of 3° C. Thereafter, the following steps A1 to A4 were carried out successively. Step A1: The bag 10 stored in an environment at 3°C ​​is taken out. Step A2: The bag 10 is held with the back surface film 15 facing downwards and is dropped repeatedly 10 times from a height of 120 cm. Step A3: The bag 10 is held with the lower portion 12 facing downwards and is dropped repeatedly 10 times from a height of 120 cm. Step A4: It is checked whether the bag 10 is broken or not. The time required to perform steps A1 to A4 consecutively on one bag 10 was approximately 2 minutes.

[0199] The above-described steps A1 to A4 were performed on 10 bags 10, and the number of bags 10 that were not broken was counted, which was 10. In other words, the pass rate was 10 / 10. In the following description, the pass rate of the drop test performed on packaging containers stored for one week in an environment of 3°C is also referred to as the low-temperature drop test pass rate.

[0200] Furthermore, some of the bags 10 after the heat sterilization treatment were stored for one week in an environment at 25° C. Thereafter, the following steps B1 to B4 were carried out successively. Step B1: The bag 10 stored in an environment at 25°C is taken out. Step B2: The bag 10 is held with the back surface film 15 facing downwards and is dropped repeatedly 10 times from a height of 120 cm. Step B3: The bag 10 is held with the lower portion 12 facing downwards and is dropped repeatedly 10 times from a height of 120 cm. Step B4: It is checked whether the bag 10 is broken or not. The time required to perform steps B1 to B4 consecutively on one bag 10 was approximately 2 minutes.

[0201] The above-described steps B1 to B4 were performed on 10 bags 10, and the number of bags 10 that were not broken was counted, which was 10. In other words, the pass rate was 10 / 10. In the following description, the pass rate of the drop test performed on packaging containers stored for one week in an environment of 25°C is also referred to as the room temperature drop test pass rate.

[0202] (Example A2) A packaging material 30 was produced in the same manner as in Example A1, except that the biaxially oriented PET film used as the second biaxially oriented plastic film 50 in Example A1 was used as the first biaxially oriented plastic film 40, and the high-stiffness PET film used as the first biaxially oriented plastic film 40 in Example A1 was used as the second biaxially oriented plastic film 50. The overall thickness of the packaging material 30 was 95 μm.

[0203] Next, in the same manner as in Example A1, the puncture strength and loop stiffness in the machine direction and perpendicular direction of the packaging material 30 were measured. As a result, the puncture strength was 16.5 N, the loop stiffness in the machine direction was 0.132 N, and the loop stiffness in the perpendicular direction was 0.110 N.

[0204] Next, in the same manner as in Example A1, bags 10 containing 200 g of water were produced using packaging material 30. Also, in the same manner as in Example A1, the bags 10 containing water were subjected to a heat sterilization treatment. Also, in the same manner as in Example A1, the drop strength of the bags 10 after the heat sterilization treatment was evaluated. As a result, the pass rates for the low-temperature drop test and the room-temperature drop test were both 10 / 10.

[0205] (Example A3) As in Example A1, a biaxially stretched PET film was prepared as the first biaxially stretched plastic film 40. Subsequently, a transparent vapor deposition layer and a gas barrier coating film were formed on the surface of the biaxially stretched PET film as follows. Subsequently, a 1 μm-thick printed layer was formed on the surface of the gas barrier coating film.

[0206] The methods for forming the transparent vapor deposition layer and the gas barrier coating film are described below. First, a roll of biaxially oriented PET film was prepared. Next, the biaxially oriented PET film was subjected to oxygen plasma treatment, and then a 12-nm-thick transparent vapor deposition layer containing aluminum oxide was formed on the oxygen plasma-treated surface. The oxygen plasma treatment and film formation process are described in detail below.

[0207] In the oxygen plasma treatment, plasma was introduced from a plasma supply nozzle in a plasma pretreatment chamber under the conditions described below onto the side of the biaxially stretched PET film on which the transparent vapor deposition layer was to be formed, and the biaxially stretched PET film was transported at a transport speed of 400 m / min and subjected to plasma pretreatment. This resulted in an oxygen plasma-treated surface on the side of the biaxially stretched PET film on which the transparent vapor deposition layer was to be formed. [Oxygen plasma pretreatment conditions] Plasma intensity: 200W·sec / m 2 Plasma formation gas ratio: oxygen / argon = 2 / 1 Voltage applied between pretreatment drum and plasma supply nozzle: 340V Vacuum level in pre-treatment compartment: 3.8Pa

[0208] In the film formation process, biaxially oriented PET film was continuously transported from the plasma pretreatment chamber and transferred to the film formation chamber. Using an aluminum target, a 12 nm thick transparent vapor deposition layer containing aluminum oxide was formed on the oxygen plasma-treated surface of the biaxially oriented PET film by vacuum deposition. A reactive resistance heating method was used as the heating method for the vacuum deposition process. The film formation conditions were as follows: [Aluminum oxide film formation conditions] ·Vacuum degree: 8.1×10 -2 Pa Conveying speed: 400m / min Oxygen gas supply: 20,000 sccm

[0209] Subsequently, a gas barrier coating film was formed on the transparent vapor deposition layer. Specifically, 385 g of water, 67 g of isopropyl alcohol, and 9.1 g of 0.5 N hydrochloric acid were mixed together to prepare a solution adjusted to pH 2.2. 175 g of tetraethoxysilane as a metal alkoxide and 9.2 g of glycidoxypropyltrimethoxysilane as a silane coupling agent were then added to the solution while cooling to 10°C to prepare solution A. Solution B was prepared by mixing 14.7 g of polyvinyl alcohol (water-soluble polymer) having a degree of polymerization of 2400 and a saponification degree of 99% or more, 324 g of water, and 17 g of isopropyl alcohol. Subsequently, the liquids A and B were mixed in a weight ratio of 6.5:3.5, and the solution thus obtained was used as a coating agent for a gas barrier coating film.

[0210] The gas barrier coating agent prepared above was spin-coated onto the transparent vapor deposition layer. The resulting film was then heated in an oven at 180°C for 60 seconds to form a gas barrier coating film with a thickness of approximately 400 nm. This resulted in a barrier laminate film comprising a biaxially stretched PET film, a transparent vapor deposition layer, and a gas barrier coating film.

[0211] Similarly to Example A1, a high-stiffness PET film was prepared as the second biaxially stretched plastic film 50. Similarly to Example A1, an unstretched polypropylene film ZK500 manufactured by Toray Advanced Film Co., Ltd. was prepared as the sealant layer 70.

[0212] Next, in the same manner as in Example A1, a first biaxially oriented plastic film 40 provided with a transparent vapor deposition layer, a gas barrier coating film, and a printed layer, a second biaxially oriented plastic film 50, and a sealant layer 70 were laminated in this order by dry lamination to produce a packaging material 30. The printed layer was laminated so as to face the surface of the second biaxially oriented plastic film 50. The overall thickness of the packaging material 30 was 95 μm.

[0213] Next, in the same manner as in Example A1, the puncture strength and loop stiffness in the machine direction and perpendicular direction of the packaging material 30 were measured. As a result, the puncture strength was 16.8 N, the loop stiffness in the machine direction was 0.132 N, and the loop stiffness in the perpendicular direction was 0.110 N.

[0214] Next, in the same manner as in Example A1, bags 10 containing 200 g of water were produced using packaging material 30. Also, in the same manner as in Example A1, the bags 10 containing water were subjected to a heat sterilization treatment. Also, in the same manner as in Example A1, the drop strength of the bags 10 after the heat sterilization treatment was evaluated. As a result, the pass rates for the low-temperature drop test and the room-temperature drop test were both 10 / 10.

[0215] (Comparative Example 1) A packaging material 30 was produced in the same manner as in Example A1, except that an unstretched polypropylene film ZK207 manufactured by Toray Advanced Film Co., Ltd. was used as the sealant layer 70. The thickness of the sealant layer 70 was 70 μm. The overall thickness of the packaging material 30 was 105 μm.

[0216] ZK207 has a high tensile modulus. Specifically, the tensile modulus of ZK207 in the machine direction (MD) is 780 MPa when the thickness is 50 μm and 680 MPa when the thickness is 60 μm. The tensile modulus of ZK207 in the transverse direction (TD) is 630 MPa when the thickness is 50 μm and 560 MPa when the thickness is 60 μm. Therefore, the product of the tensile modulus (MPa) and thickness (μm) of ZK207 in the machine direction is 39,000 when the thickness is 50 μm and 40,800 when the thickness is 60 μm. The product of the tensile modulus (MPa) and thickness (μm) of ZK207 in the transverse direction is 31,500 when the thickness is 50 μm and 33,600 when the thickness is 60 μm.

[0217] ZK207 also has low tensile elongation. Specifically, the tensile elongation of ZK207 in the machine direction (MD) is 790% when the thickness is 50 μm and 730% when the thickness is 60 μm. The tensile elongation of ZK207 in the transverse direction (TD) is 1020% when the thickness is 50 μm and 870% when the thickness is 60 μm. Therefore, the product of the tensile elongation (%) of ZK207 in the machine direction and the thickness (μm) is 39,500 when the thickness is 50 μm and 43,800 when the thickness is 60 μm. The product of the tensile elongation (%) of ZK207 in the transverse direction and the thickness (μm) is 51,000 when the thickness is 50 μm and 52,200 when the thickness is 60 μm.

[0218] Next, in the same manner as in Example A1, the puncture strength and loop stiffness in the machine direction and perpendicular direction of the packaging material 30 were measured. As a result, the puncture strength was 15.6 N, the loop stiffness in the machine direction was 0.182 N, and the loop stiffness in the perpendicular direction was 0.153 N.

[0219] Next, in the same manner as in Example A1, bags 10 containing 200 g of water were produced using packaging material 30. Also, in the same manner as in Example A1, the bags 10 containing water were subjected to a heat sterilization treatment. Also, in the same manner as in Example A1, the drop strength of bags 10 after the heat sterilization treatment was evaluated. As a result, the pass rate for the low-temperature drop test was 7 / 10, and the pass rate for the room-temperature drop test was 9 / 10.

[0220] (Comparative Example 2) A packaging material 30 was produced in the same manner as in Comparative Example 1, except that the biaxially oriented PET film used as the second biaxially oriented plastic film 50 in Comparative Example 1 was used as the first biaxially oriented plastic film 40, and the high-stiffness PET film used as the first biaxially oriented plastic film 40 in Comparative Example 1 was used as the second biaxially oriented plastic film 50. The overall thickness of the packaging material 30 was 105 μm.

[0221] Next, in the same manner as in Example A1, the puncture strength and loop stiffness in the machine direction and perpendicular direction of the packaging material 30 were measured. As a result, the puncture strength was 15.4 N, the loop stiffness in the machine direction was 0.180 N, and the loop stiffness in the perpendicular direction was 0.155 N.

[0222] Next, in the same manner as in Example A1, bags 10 containing 200 g of water were produced using packaging material 30. Also, in the same manner as in Example A1, the bags 10 containing water were subjected to a heat sterilization treatment. Also, in the same manner as in Example A1, the drop strength of bags 10 after the heat sterilization treatment was evaluated. As a result, the pass rate for the low-temperature drop test was 7 / 10, and the pass rate for the room-temperature drop test was 9 / 10.

[0223] (Comparative Example 3) A packaging material 30 was produced in the same manner as in Example A1, except that the biaxially oriented PET film used as the second biaxially oriented plastic film 50 in Example A1 was used as the first biaxially oriented plastic film 40. The overall thickness of the packaging material 30 was 91 μm.

[0224] Subsequently, the puncture strength of the packaging material 30 was measured in the same manner as in Example A1. As a result, the puncture strength was 13.7 N.

[0225] Next, in the same manner as in Example A1, bags 10 containing 200 g of water were produced using packaging material 30. Also, in the same manner as in Example A1, the bags 10 containing water were subjected to a heat sterilization treatment. Also, in the same manner as in Example A1, the drop strength of the bags 10 after the heat sterilization treatment was evaluated. As a result, the pass rates for the low-temperature drop test and the room-temperature drop test were both 10 / 10.

[0226] The layer structures and evaluation results of the packaging materials 30 of Examples A1 to A3 are shown together in Figure 20. The layer structures and evaluation results of the packaging materials 30 of Comparative Examples 1 to 3 are shown together in Figure 21. In Figures 20 and 21, the "Layer Structure" column lists the components of the packaging material 30 in order from the outer layer to the top.

[0227] As can be seen from a comparison between Examples A1 to A3 and Comparative Example 3, when the packaging material 30 contained a high-stiffness polyester film, the puncture strength of the packaging material 30 was increased compared to when the packaging material 30 did not contain a high-stiffness polyester film. Specifically, the puncture strength could be increased to 14.0 N or more. In Examples A1 to A3, the puncture strength of the packaging material 30 was 16.0 N or more.

[0228] As can be seen from Examples A1 to A3, when the loop stiffness of packaging material 30 in at least one direction was less than 0.150 N, the pass rates for the low-temperature drop test and the room-temperature drop test conducted after retort treatment were both 10 / 10. In Examples A1 to A3, the loop stiffness of packaging material 30 in both the machine direction and the perpendicular direction was less than 0.150 N. On the other hand, as can be seen from Comparative Examples 1 and 2, when the loop stiffness of packaging material 30 in the machine direction and the perpendicular direction was 0.150 N or more, some bags 10 broke in the drop test. From these findings, it is believed that a loop stiffness of packaging material 30 less than 0.150 N and appropriate flexibility of packaging material 30 contribute to improving the drop strength of bags 10 after retort treatment.

[0229] Example B1 As in Example A1, a high-stiffness PET film having a thickness of 16 μm was prepared as the first biaxially oriented plastic film 40. Then, as in Example A3, a transparent vapor deposition layer and a gas barrier coating film were formed on the surface of the first biaxially oriented plastic film 40. Then, a printed layer having a thickness of 1 μm was formed on the surface of the gas barrier coating film.

[0230] As the second biaxially stretched plastic film 50, a biaxially stretched PET film having a thickness of 12 μm was prepared in the same manner as in Example A1.

[0231] Furthermore, as the sealant layer 70, a sealant film (thickness: 50 μm) made of a mixed resin containing low-density polyethylene and linear low-density polyethylene and having a melting point of 105° C. was prepared.

[0232] Next, the first biaxially oriented plastic film 40, the second biaxially oriented plastic film 50, and the sealant layer 70 were laminated in this order by dry lamination to produce the packaging material 30. The printed layer was laminated so that it faced the surface of the second biaxially oriented plastic film 50. A two-component polyurethane adhesive (main agent: RU-40, curing agent: H-4) manufactured by Rock Paint Co., Ltd. was used for the first adhesive layer 45 and the second adhesive layer 55. The main agent RU-40 is a polyester polyol. The thickness of the first adhesive layer 45 and the second adhesive layer 55 was 3 μm. The overall thickness of the packaging material 30 was 85 μm.

[0233] Next, in the same manner as in Example A1, the puncture strength and loop stiffness in the machine direction and perpendicular direction of the packaging material 30 were measured. As a result, the puncture strength was 16.5 N, the loop stiffness in the machine direction was 0.111 N, and the loop stiffness in the perpendicular direction was 0.121 N.

[0234] Next, bags 10 containing 200 g of water were produced using packaging material 30 in the same manner as in Example A1, except that the heat sealing temperature of the heat sealing device was set to 180°C. Furthermore, the bags 10 containing water were subjected to a heat sterilization treatment. Specifically, the bags 10 were subjected to a boiling treatment. The boiling temperature was 95°C, and the boiling time was 60 minutes. Furthermore, the drop strength of the bags 10 after the heat sterilization treatment was evaluated in the same manner as in Example A1. As a result, the pass rates for the low-temperature drop test and the room-temperature drop test were both 10 / 10.

[0235] (Example B2) A packaging material 30 was produced in the same manner as in Example B1, except that the biaxially oriented PET film used as the second biaxially oriented plastic film 50 in Example B1 was used as the first biaxially oriented plastic film 40, and the high-stiffness PET film used as the first biaxially oriented plastic film 40 in Example A1 was used as the second biaxially oriented plastic film 50. The overall thickness of the packaging material 30 was 85 μm.

[0236] Next, in the same manner as in Example A1, the puncture strength and loop stiffness in the machine direction and perpendicular direction of the packaging material 30 were measured. As a result, the puncture strength was 16.4 N, the loop stiffness in the machine direction was 0.114 N, and the loop stiffness in the perpendicular direction was 0.123 N.

[0237] Next, in the same manner as in Example B1, bags 10 containing 200 g of water were produced using packaging material 30. Also, in the same manner as in Example B1, the bags 10 containing water were subjected to a heat sterilization treatment. Also, in the same manner as in Example B1, the drop strength of the bags 10 after the heat sterilization treatment was evaluated. As a result, the pass rates for the low-temperature drop test and the room-temperature drop test were both 10 / 10.

[0238] (Example B3) A packaging material 30 was produced in the same manner as in Example B1, except that a transparent vapor deposition layer and a gas barrier coating film were not provided on the high-stiffness PET film constituting the first biaxially stretched plastic film 40. The overall thickness of the packaging material 30 was 85 μm.

[0239] Next, in the same manner as in Example A1, the puncture strength and loop stiffness in the machine direction and perpendicular direction of the packaging material 30 were measured. As a result, the puncture strength was 16.5 N, the loop stiffness in the machine direction was 0.111 N, and the loop stiffness in the perpendicular direction was 0.121 N.

[0240] Next, in the same manner as in Example B1, bags 10 containing 200 g of water were produced using packaging material 30. Also, in the same manner as in Example B1, the bags 10 containing water were subjected to a heat sterilization treatment. Also, in the same manner as in Example B1, the drop strength of the bags 10 after the heat sterilization treatment was evaluated. As a result, the pass rates for the low-temperature drop test and the room-temperature drop test were both 10 / 10.

[0241] The layer structures and evaluation results of the packaging materials 30 of Examples B1 to B3 are summarized in Figure 22. In Examples B1 to B3, the packaging materials 30 contained high-stiffness polyester films, which enabled the puncture strength of the packaging materials 30 to be increased to 14.0 N or more. In Examples B1 to B3, the puncture strength of the packaging materials 30 was 16.0 N or more.

[0242] As can be seen from Examples B1 to B3, when the loop stiffness of the packaging material 30 in at least one direction was less than 0.150 N, the pass rates for the low-temperature drop test and the room-temperature drop test conducted after the boiling treatment were both 10 / 10. In Examples B1 to B3, the loop stiffness of the packaging material 30 in both the machine direction and the perpendicular direction was less than 0.150 N. From these findings, it is believed that a loop stiffness of the packaging material 30 of less than 0.150 N and the appropriate flexibility of the packaging material 30 also contribute to improving the drop strength of the bag 10 after the boiling treatment.

[0243] Example C1 A packaging material 30 was produced in the same manner as in Example B1, except that a co-extruded film having easy-peel properties and including a first layer 71 and a second layer 72 as shown in FIG. 12 was used as the sealant layer 70. The first layer 71 was a 45 μm thick layer made of polyethylene. The second layer 72 was a 5 μm thick layer containing a mixed resin of polyethylene and polypropylene. The polyethylene had a density of 0.950 g / cm. 3High-density polyethylene having a density of 1000 MPa was used. An ethylene-propylene random copolymer was used as the polypropylene. The mass ratio of polypropylene to polyethylene in the second layer 72 was 7:3. The thickness of the sealant layer 70 was 50 μm. The overall thickness of the packaging material 30 was 85 μm.

[0244] Subsequently, in the same manner as in Example A1, the puncture strength and loop stiffness in the machine direction and perpendicular direction of the packaging material 30 were measured. As a result, the puncture strength was 16.2 N, the loop stiffness in the machine direction was 0.112 N, and the loop stiffness in the perpendicular direction was 0.115 N.

[0245] Next, the packaging material 30 was used as a lid material 114 to produce a lidded container 110 shown in FIGS. 18A and 18B.

[0246] First, the container body 112 was prepared. An ethylene-propylene block copolymer was used as the material for the container body 112. The inner dimension R1 of the flange portion 113 of the container body 112 was 60 mm, the outer dimension R2 of the flange portion 113 was 70 mm, and the height R3 of the container body 112 was 110 mm.

[0247] Next, 200 g of water was filled into container body 112 as the contents, and then lid member 114 made of packaging material 30 was heat-sealed to the upper surface of flange portion 113 of container body 112 to form seal portion 116. Sealed portion 116 had a width R4 of 5 mm. In this manner, a plurality of lidded containers 110 containing 200 g of water, as shown in Figures 18A and 18B, were produced.

[0248] In the process of producing the lidded container 110, a heat sealer TP-701-A manufactured by Tester Sangyo Co., Ltd. was used as the heat sealing device for forming the sealed portion 116. The heat sealing conditions were as follows. Heat sealing temperature: 180℃ Heat sealing time: 1.5 seconds Heat sealing pressure: 0.5MPa

[0249] Next, the lidded container 110 containing the water was subjected to a heat sterilization treatment. Specifically, a spray-type retort treatment was performed on the lidded container 110. The retort temperature was 121°C, and the retort time was 30 minutes.

[0250] Next, some of the plurality of lidded containers 110 after heat sterilization treatment were stored for one week in an environment at 3° C. Thereafter, the following steps C1 to C3 were carried out successively. Step C1: The lidded container 110 stored in an environment at 3°C ​​is taken out. Step C2: The lidded container 110 is held so that the side surface 112b is parallel to the horizontal direction and is dropped twice repeatedly from a height of 60 cm. Step C3: It is checked whether water is leaking from the container 110 with lid.

[0251] The above-described steps C1 to C3 were performed on 10 lidded containers 110, and the number of lidded containers 110 that did not leak water was counted, and it was found to be 10. In other words, the pass rate for the low-temperature drop test was 10 / 10.

[0252] Furthermore, some of the plurality of lidded containers 110 after heat sterilization treatment were stored for one week in an environment at 25° C. Thereafter, the following steps D1 to D3 were carried out successively. Step D1: The lidded container 110 stored in an environment at 25°C is taken out. Step D2: The lidded container 110 is held so that the side surface 112b faces horizontally and is dropped twice repeatedly from a height of 60 cm. Step D3: It is checked whether water is leaking from the container 110 with lid.

[0253] The above-described steps D1 to D3 were performed on 10 lidded containers 110, and the number of lidded containers 110 that did not leak water was counted, and it was found to be 10. In other words, the room temperature drop test pass rate was 10 / 10.

[0254] (Example C2) A packaging material 30 was produced in the same manner as in Example C1, except that the biaxially oriented PET film used as the second biaxially oriented plastic film 50 in Example C1 was used as the first biaxially oriented plastic film 40, and the high-stiffness PET film used as the first biaxially oriented plastic film 40 in Example C1 was used as the second biaxially oriented plastic film 50. The overall thickness of the packaging material 30 was 85 μm.

[0255] Next, in the same manner as in Example A1, the puncture strength and loop stiffness in the machine direction and perpendicular direction of the packaging material 30 were measured. As a result, the puncture strength was 16.3 N, the loop stiffness in the machine direction was 0.114 N, and the loop stiffness in the perpendicular direction was 0.119 N.

[0256] Next, in the same manner as in Example C1, a lidded container 110 containing 200 g of water was produced using the packaging material 30 as the lid member 114. Also, in the same manner as in Example C1, the lidded container 110 containing water was subjected to a heat sterilization treatment. Also, in the same manner as in Example C1, the drop strength of the lidded container 110 after the heat sterilization treatment was evaluated. As a result, the pass rates for the low-temperature drop test and the room-temperature drop test were both 10 / 10.

[0257] (Example C3) A packaging material 30 was produced in the same manner as in Example C1, except that a transparent vapor deposition layer and a gas barrier coating film were not provided on the high-stiffness PET film constituting the first biaxially stretched plastic film 40. The overall thickness of the packaging material 30 was 85 μm.

[0258] Subsequently, in the same manner as in Example A1, the puncture strength and loop stiffness in the machine direction and perpendicular direction of the packaging material 30 were measured. As a result, the puncture strength was 16.2 N, the loop stiffness in the machine direction was 0.112 N, and the loop stiffness in the perpendicular direction was 0.115 N.

[0259] Next, in the same manner as in Example C1, a lidded container 110 containing 200 g of water was produced using the packaging material 30 as the lid member 114. Also, in the same manner as in Example C1, the lidded container 110 containing water was subjected to a heat sterilization treatment. Also, in the same manner as in Example C1, the drop strength of the lidded container 110 after the heat sterilization treatment was evaluated. As a result, the pass rates for the low-temperature drop test and the room-temperature drop test were both 10 / 10.

[0260] The layer structures and evaluation results of the packaging materials 30 of Examples C1 to C3 are summarized in Figure 23. In Examples C1 to C3, the packaging materials 30 contained high-stiffness polyester films, which enabled the puncture strength of the packaging materials 30 to be increased to 14.0 N or more. In Examples C1 to C3, the puncture strength of the packaging materials 30 was 16.0 N or more.

[0261] As can be seen from Examples C1 to C3, when the loop stiffness of the packaging material 30 in at least one direction was less than 0.150 N, the pass rates for the low-temperature drop test and the room-temperature drop test conducted on the lidded container 110 after retort treatment were both 10 / 10. In Examples C1 to C3, the loop stiffness of the packaging material 30 in both the flow direction and the perpendicular direction was less than 0.150 N. From these findings, it is believed that a loop stiffness of the packaging material 30 of less than 0.150 N and the appropriate flexibility of the packaging material 30 also contribute to improving the drop strength of the lidded container 110 after retort treatment. [Explanation of symbols]

[0262] 10 bags 11 Upper 12 Lower 12a Lower seal 13 Side 13a Side seal 14 Surface film 15 Back film 16 Lower film 17 Storage section 18 Contents 20 Steam release mechanism 20a Steam release seal 25 Easy-to-open means 26 notches 30 Packaging materials 32 Printing layer 34 Deposited layer 36 Gas barrier coating film 40 First biaxially stretched plastic film 45 First adhesive layer 50 Second biaxially stretched plastic film 55 Second adhesive layer 70 Sealant Layer

Claims

1. A packaging material comprising, in order from the outer surface side to the inner surface side, at least a first biaxially oriented plastic film, a second biaxially oriented plastic film, and a sealant layer, The first biaxially oriented plastic film and the second biaxially oriented plastic film contain polyester as a main component, One of the first biaxially oriented plastic film and the second biaxially oriented plastic film is a high-stiffness polyester film having a loop stiffness of 0.0017 N or more in at least one direction; The loop stiffness of the packaging material in one direction is less than 0.150 N; A packaging material having a puncture strength of 14.0 N or more.

2. The packaging material according to claim 1 , wherein the first biaxially oriented plastic film and the second biaxially oriented plastic film each contain polyethylene terephthalate as a primary component.

3. The packaging material according to claim 1 or 2, comprising a printed layer.

4. 4. The packaging material according to claim 1, comprising: a vapor deposition layer located on the surface of the first biaxially oriented plastic film or the surface of the second biaxially oriented plastic film; and a gas barrier coating film located on the vapor deposition layer.

5. The packaging material according to claim 1 , wherein the packaging material has a puncture strength of 16.0 N or more.

6. The packaging material according to claim 1 , wherein the sealant layer contains polypropylene as a main component.

7. The packaging material according to claim 1 , wherein the sealant layer comprises polyethylene having a melting point of 100° C. or higher.

8. 6. The packaging material according to claim 1, wherein the sealant layer comprises a first layer containing polyethylene or polypropylene as a main component, and a second layer located on the inner side of the first layer and containing a mixed resin of polyethylene and polypropylene.

9. A retort pouch comprising the packaging material according to any one of claims 1 to 8.

10. A microwave pouch having a storage section, A packaging material according to any one of claims 1 to 8; a seal portion joining the inner surfaces of the packaging material together, the seal portion including a steam release seal portion that peels off due to an increase in pressure in the containing portion.

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