Laminate, packaging bag and package

Abstract

To provide a laminate having sufficiently high piercing strength and to provide a packaging bag and a package provided with such a laminate.SOLUTION: There is provided a laminate 100 which includes a polyester film as a base material film 10 and a sealant layer 30, wherein the average value of the birefringence index of the polyester film is 0.02 or more. Further, there are provided a packaging bag 200 provided with such a laminate 100 and a package provided with the packaging bag 200 and a storage object stored in a storage part of the packaging bag 200.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a laminate, a packaging bag, and a packaging body. [Background technology]

[0002] It is known that the birefringence of a base film affects the physical properties of the base film. For example, Patent Document 1 describes that when the birefringence value of a biaxially oriented polyester film increases, the pinhole resistance decreases. Patent Document 2 describes that the heat sealability, thermal dimensional stability, and tearability can be improved by adjusting the birefringence value of a polypropylene-based sealant film. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2007-118476 A [Patent Document 2] JP 2022-042574 A Summary of the Invention [Problem to be solved by the invention]

[0004] A laminate including a base film is required to have high puncture strength because it is used for packaging bags and the like. On the other hand, the molecular orientation of a polyester film used as a base film changes when stretched. Therefore, there is a concern that the puncture strength of the base film is affected by the molecular orientation, and therefore, there is a concern that the puncture strength of a laminate using such a base film is also affected. Therefore, the present disclosure provides a laminate having a sufficiently high puncture strength, and a packaging bag and a packaging body including such a laminate. [Means for solving the problem]

[0005] One aspect of the present disclosure provides a laminate including a polyester film as a base film and a sealant layer, the polyester film having an average birefringence of 0.02 or more.

[0006] The laminate includes a polyester film having an average birefringence of 0.02 or more as a base film. A base film having an average birefringence of 0.02 or more has sufficiently high puncture strength. Therefore, by using such a base film, a laminate having improved puncture strength can be obtained.

[0007] According to one aspect of the present disclosure, there is provided a packaging bag including the laminate. By including the laminate, the packaging bag has high puncture strength.

[0008] One aspect of the present disclosure provides a package including the packaging bag described above and an item to be contained in the container of the packaging bag. The package includes the laminate described above, and thus has high puncture strength. Effect of the Invention

[0009] The present disclosure can provide a laminate having sufficiently high puncture strength, as well as a packaging bag and a packaging body including such a laminate. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a diagram showing an example of a cross section of a laminate. [Diagram 2] FIG. 2 is a diagram showing an example of a method for cutting a stretched film in the TD direction. [Diagram 3] FIG. 2 is a diagram showing an example of a cross section of a laminate. [Figure 4] FIG. 1 is a diagram showing an example of a packaging bag. [Diagram 5] FIG. 1 is a diagram showing the birefringence values ​​at various positions on an MR-PET film. [Figure 6] FIG. 1 shows the absolute values ​​of the orientation angles at each position on the MR-PET film. [Figure 7]FIG. 1 is a graph showing the puncture strength values ​​at each cutting position of an MR-PET film. [Figure 8] FIG. 1 is a diagram showing the birefringence values ​​at various positions on a general PET film. [Figure 9] FIG. 2 is a diagram showing the absolute values ​​of the orientation angle at each position of a general PET film. [Figure 10] FIG. 1 is a graph showing the puncture strength of a general PET film at each cutting position. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the embodiments of the present disclosure will be described. However, the following embodiments are examples for explaining the present disclosure, and are not intended to limit the present disclosure to the following contents. The upper or lower limit of the numerical range specified in this specification may be replaced with any value shown in the examples. In addition, the upper and lower limit values ​​described individually may be arbitrarily combined. Unless otherwise specified, the materials or components exemplified in this specification may be used alone or in combination of two or more types. In the description, the same elements or elements having the same functions are given the same reference numerals, and duplicated descriptions are omitted. In addition, the positional relationships such as up, down, left, and right used in the description are based on the positional relationships shown in the drawings, unless otherwise specified.

[0012] 1 is a diagram showing an example of a cross section of a laminate according to one embodiment. The laminate 100 has a sealant layer 30 on one surface of a base film 10. An adhesive layer S is interposed between the base film 10 and the sealant layer 30.

[0013] The laminate 100 includes a polyester film as a base film 10. The polyester film may be, for example, a polyethylene terephthalate (PET) film. The polyester film may be a recycled polyester film that has been subjected to a recycling process. Examples of recycled polyester films include mechanically recycled polyester films such as mechanically recycled polyethylene terephthalate films (MR-PET films) and chemically recycled polyester films such as chemically recycled polyethylene terephthalate films (CR-PET films).

[0014] MR-PET film can be obtained by crushing and washing PET, treating it at high temperature and reduced pressure for a certain period of time, removing impurities by melt filtration, turning it back into PET resin, and processing it into film. CR-PET film can be obtained by crushing and washing PET, and chemically decomposing it to obtain PET raw material, turning it back into PET resin, and processing it into film. By using the recycled PET film produced through these recycling processes as the base film 10, the consumption of plastic resources and the CO2 emitted during PET production can be reduced. 2 It is possible to obtain an environmentally friendly laminate 100 that reduces emissions.

[0015] The thickness of the base film 10 may be 9 to 100 μm, 9 to 25 μm, or 12 to 16 μm. The thickness of the base film 10 may be adjusted depending on the application or the desired characteristics. If the thickness is too thick, the sealing performance during packaging may decrease, and the flexibility of the package may decrease, which may cause problems during packaging. If the thickness is too thin, the package may not have sufficient stiffness, and problems such as wrinkles may easily occur during packaging.

[0016] The base film 10 may be cut out from a stretched film in order to orient the molecules in the base film 10 and improve the puncture strength. The stretching direction may be either the MD direction or the TD direction. The stretching method may be any method that can provide a film with stable dimensions, such as uniaxial stretching or biaxial stretching. In the case of biaxial stretching, it is preferable to stretch in the MD direction and then in the TD direction.

[0017] A stretched film is deformed anisotropically due to the bowing phenomenon during stretching, which causes the molecular orientation to change depending on the position of the film in the stretching direction. In general, the degree of molecular orientation tends to increase from the center to the end in the stretching direction. Therefore, when cutting out the base film 10 from the stretched film, the base film 10 has different properties such as birefringence and orientation angle depending on the cutting position of the base film 10.

[0018] An example of the position of the base film 10 in the stretched film will be described with reference to FIG. 2. FIG. 2 is a diagram showing one end of the stretched film 105 in the MD direction. The stretched film 105 can be cut along a first virtual line VL1 extending parallel to the MD direction of the stretched film 105 and a second virtual line VL2 extending parallel to the TD direction to obtain a plurality of cut films 11. The cut films 11 to be cut may have any size and may have any shape, not limited to a rectangle. By cutting the cut film 11 so that the positions in the TD direction are different from each other, cut films 11 with different molecular orientations can be obtained due to differences in the degree of stretching in the TD direction.

[0019] As shown in FIG. 2, five cut films 11 are cut out from one side edge of the stretched film 105 parallel to the MD direction to the other side edge, in order as position numbers #1, #2, #3, #4, and #5. In this example, five cut films 11 are cut out, but the number of cut films may be six or more or four or less. The cut films 11 with different position numbers have different degrees of stretching and therefore different physical properties. For example, the cut film 11 (#1) on one side edge side and the cut film 11 (#5) on the other side edge side cut out from the stretched film 105 are more affected by the bowing phenomenon than the cut film 11 (#3) in the center, so that they have relatively large molecular orientation and high puncture strength. Therefore, the laminate 100 using the cut film 11 (#1) or the cut film 11 (#5) as the base film 10 has sufficiently high puncture strength.

[0020] In the case of biaxial stretching, the length of the stretched film 105 in the MD direction is usually sufficiently longer than the length in the TD direction, so that the effect of stretching in the MD direction can be ignored.

[0021] Among the multiple cut films 11, those having an average value of birefringence of 0.02 or more can be used as the base film 10. The average value of birefringence of the base film 10 may be 0.05 or less, or may be 0.04 or less. The average value of birefringence is calculated for each base film 10 (each cut film 11). For example, the average value may be calculated from the measured values ​​of each of the multiple base films 10 cut out from one cutting position, or the average value may be calculated from multiple measured values ​​measured at multiple points on one base film 10 (cut film 11). The relative standard deviation may be calculated from the calculated average value and the number of measurements. The number of measurement points may be 5 or more, or may be 10 or more. In order to suppress the variation in the average value, the number of measurement points may be 20 or less. When the average value of birefringence of the base film 10 is increased, the number of oriented molecules of the base film 10 is increased, and the puncture strength is improved. The laminates 100 and 101 including such base films 10 have high puncture strength.

[0022] The birefringence of the base film 10 is calculated as the difference between the refractive index nx in the x direction and the refractive index ny in the y direction, as shown in the following formula (1), where the direction showing the highest refractive index in the in-plane direction of the base film 10, i.e., the direction perpendicular to the thickness direction of the base film 10, is the x direction, and the direction perpendicular to the x direction is the y direction. The x direction (the in-plane direction showing the highest refractive index) may be the MD direction of the base film 10. The birefringence of the film can be measured, for example, using a "KOBRA-WR retardation measurement device" (manufactured by Oji Scientific Instruments Co., Ltd.). Birefringence = nx-ny (1)

[0023] The absolute value of the orientation angle of the base film 10 may be 80° or less, 70° or less, or 60° or less. The absolute value of the orientation angle may be 45° or more, or 50° or more. When the absolute value of the orientation angle is within the above range, the molecules in the base film 10 are oriented and some of the molecular chains tend to overlap in the thickness direction, improving the puncture strength of the film. A laminate 100 including such a base film 10 has even higher puncture strength.

[0024] The average absolute value of the orientation angle of the base film 10 may be 80° or less, 70° or less, or 60° or less. The average absolute value of the orientation angle may be 45° or more, or 50° or more. The average value and relative standard deviation can be calculated by the same procedure as described in the measurement of birefringence. When the average absolute value of the orientation angle is in the above range, the molecules in the base film 10 are oriented, and a part of the molecular chains is easily overlapped in the thickness direction, thereby improving the puncture strength of the film. The laminate 100 including such a base film 10 has a higher puncture strength.

[0025] The orientation angle can be calculated by subtracting the smaller of the angles between the long axis of the molecule rotated counterclockwise or clockwise by stretching and the stretching direction from 90°. Therefore, the molecules in the center of the film along the stretching direction are hardly oriented, so the orientation angle is close to 90°, and the orientation angle of the molecules becomes smaller toward the end of the film because the angle at which the long axis of the molecule rotates becomes larger. The orientation angle can be measured, for example, using the same "KOBRA-WR phase difference measuring device" (manufactured by Oji Scientific Instruments Co., Ltd.: measurement area 5 mm diameter) as the birefringence measuring device. The measured value of the orientation angle is positive when the sample rotates counterclockwise with the MD direction of the sample as the angle reference 0°, and negative when the sample rotates clockwise, and the positive and negative are reversed depending on the rotation direction, so the orientation angle is expressed as the absolute value of the measured value.

[0026] The cut film 11 (#1) cut from one side edge of the above-mentioned stretched film 105 has a higher degree of molecular orientation than the cut film 11 (#3), and therefore has a higher birefringence and a smaller orientation angle. Therefore, based on the value of the birefringence or orientation angle, the cut film 11 with a high degree of molecular orientation can be used as the base film 10. The base film 10 with a high degree of orientation has more overlap in the thickness direction of the molecules, improving its puncture strength. Therefore, the laminates 100, 101 including such a base film 10 have high puncture strength.

[0027] The puncture strength of the base film 10 and the laminates 100, 101 can be measured based on "7.5 Puncture Strength Test" of JIS Z1707:2019 "General Rules for Food Packaging Plastic Films". The measurement can be performed using, for example, Tensilon AD-7303 (manufactured by A&D Co., Ltd.). The puncture strength of the base film 10 may be 7.0 N or more, or 7.8 N or more. By using such a base film 10, the puncture strength of the laminates 100, 101 can be improved. The puncture strength of the base film 10 may be 9.0 N or less.

[0028] The puncture strength of the laminate 100, 101 can be measured by piercing the laminate 100, 101 from the surface on the base film 10 side toward the opposite side. The puncture strength of the laminate 100, 101 may be 8.5 N or more, or may be 8.60 N or more. By providing a laminate having such a puncture strength, a packaging bag and a packaging body having high puncture strength can be obtained. The puncture strength of the laminate 100, 101 may be 10.0 N or less.

[0029] The sealant layer 30 is a layer that imparts heat-sealing properties to the laminate 100. Examples of components of the sealant layer 30 include thermoplastic resins, specifically, polyolefin resins such as low-density polyethylene (LDPE), medium-density polyethylene (MDPE), linear low-density polyethylene (LLDPE), ethylene-vinyl acetate copolymer (EVA), and ethylene-α-olefin copolymer, ethylene resins such as ethylene-(meth)acrylic acid copolymer, blend resins of polyethylene and polybutene, homopolypropylene resin (PP), propylene-ethylene random copolymer, propylene-ethylene block copolymer, and polypropylene resins such as propylene-α-olefin copolymer, etc. In addition, the sealant layer 30 may contain one of a plurality of types of these thermoplastic resins alone or in combination.

[0030] The resin constituting the sealant layer 30 may contain various additives such as a flame retardant, a slip agent, an antiblocking agent, an antioxidant, a light stabilizer, and a tackifier.

[0031] The thickness of the sealant layer 30 is preferably adjusted depending on the mass of the contents, the shape of the packaging bag, etc. The thickness of the sealant layer 30 is preferably, for example, 10 to 100 μm.

[0032] An adhesive layer S is interposed between the base film 10 and the sealant layer 30. Examples of adhesive materials that can be used include polyester-isocyanate resins, urethane resins, and polyether resins. By interposing the adhesive layer S, the base film 10 and the sealant layer 30 can be bonded more firmly.

[0033] The thickness of the adhesive layer S is not particularly limited and may be, for example, 0.5 to 5 μm or 2 to 3 μm. When the thickness of the adhesive layer S is 0.5 μm or more, the adhesion between the base film 10 and the sealant layer 30 can be improved, and when it is 5 μm or less, the laminate 100 can be easily recycled.

[0034] Examples of methods for forming the laminate 100 include a dry lamination method in which a film-like sealant layer 30 made of the above-mentioned thermoplastic resin is laminated onto the base film 10 using an adhesive such as a one-component curing or two-component curing urethane adhesive, a non-solvent dry lamination method in which a film-like sealant layer 30 is laminated onto the base film 10 using a solvent-free adhesive, and an extrusion lamination method in which the above-mentioned thermoplastic resin is heated and melted, extruded into a curtain shape, and laminated. The adhesive used to laminate the sealant layer 30 onto the base film 10 forms an adhesive layer S as shown in FIG. 1. The sealant layer 30 may be directly laminated onto the base film 10 without the adhesive layer S.

[0035] A printing layer can be provided on the surface of the base film 10 on the side of the sealant layer 30. The printing layer is provided at a position visible from the outside of the laminate for the purpose of displaying information about the contents, identifying the contents, or improving the design of the packaging bag. The printing method and printing ink are not particularly limited, and are appropriately selected from known printing methods and printing inks in consideration of printability on the film, design such as color tone, adhesion, safety as a food container, etc. Examples of printing methods that can be used include gravure printing, offset printing, gravure offset printing, flexographic printing, and inkjet printing. Of these printing methods, gravure printing is preferred from the viewpoints of productivity and high definition of the pattern.

[0036] In order to improve the adhesion of the printed layer, the surface of the base film 10 on the printed layer side may be subjected to various pretreatments such as corona treatment, plasma treatment, and frame treatment, or a coating layer such as an easy-adhesion layer may be provided.

[0037] Fig. 3 is a diagram showing an example of a cross section of a laminate according to another embodiment of the present disclosure. As shown in Fig. 3, the laminate 101 includes an intermediate layer 20 between the base film 10 and the sealant layer 30. The configuration of the intermediate layer 20 can be appropriately referred to the contents described in the configuration of the sealant layer 30. By including the intermediate layer 20 in the laminate 101, deformation of the laminate during the production of a packaging bag can be further reduced. A plurality of intermediate layers 20 may be used depending on the application of the laminate 101.

[0038] As shown in Fig. 3, a metal layer 40 may be laminated between the intermediate layer 20 and the sealant layer 30. The metal layer 40 may be laminated between the base film 10 and the intermediate layer 20, taking into consideration the manufacturing conditions. By providing the laminate 101 with the metal layer 40, the puncture strength and gas barrier properties of the laminate can be improved. In addition, the metal layer 40 may be vapor-deposited on the intermediate layer 20 in advance.

[0039] An anchor coat layer may be provided adjacent to at least one selected from the printed layer and the metal layer 40. By providing the anchor coat layer, the adhesion of the printed layer or the metal layer 40 can be increased, and the puncture strength of the laminate 100, 101 can be further improved. The anchor coat layer can be formed by applying an anchor coat agent onto a predetermined layer and drying it. For example, polyester-based polyurethane resin, polyether-based polyurethane resin, etc. can be used as the anchor coat agent. The thickness of the anchor coat layer is not particularly limited, but may be 0.1 to 1 μm, or 0.3 to 0.5 μm.

[0040] As the metal layer 40, a known metal foil such as copper foil or aluminum foil can be used. From the viewpoint of improving the gas barrier property or preventing the transmission of visible light and ultraviolet light, it is preferable to use aluminum foil. The thickness of the metal layer 40 may be, for example, 6 to 9 μm. By making the thickness of the metal layer 40 6 μm or more, the piercing strength of the laminate 101 is improved. Therefore, even if a foreign object is attached to the base film 10 in a package including the laminate 101, the problem of the foreign object penetrating inside the base film 10 can be prevented. Therefore, deterioration of the quality of the contained contents can be suppressed.

[0041] 4 is an example of a packaging bag formed using a laminate. The packaging bag 200 includes a sealed portion 211 formed by bonding together the peripheries of a pair of substantially rectangular laminates 100, and a storage portion 218 formed between the pair of laminates 100, 100 by the sealed portion 211. That is, the packaging bag 200 has a side end portion 214, a lower end portion 216, and an upper end portion 217 sealed by the sealed portion 211. The packaging bag 200 includes a storage portion 218 in which an object such as food is stored, in a non-sealed portion 215 surrounded by the sealed portion 211. The object such as food is enclosed in the storage portion 218. The sealed portion 211 at the lower end portion 216 may be sealed after the object is filled in the storage portion 218.

[0042] The pair of laminates 100 are overlapped with the sealant layers 30 facing each other. The pair of laminates 100 may be bonded to each other at the seal portion 211 by an adhesive. The pair of laminates 100 may form the seal portion 211 by bonding the heat seal layers provided on the sealant layers 30 to each other.

[0043] The laminate 100 has a high puncture strength, and therefore can sufficiently prevent the formation of through holes. This can sufficiently prevent trace components, PET components, outside air, and the like from entering the inside of the packaging bag 200 through the through holes, thereby sufficiently preventing contamination or deterioration of the contents contained in the containing section 218. The packaging bag 200 may have an arbitrary layer on the base film 10 and the sealant layer 30 of the laminate 100.

[0044] The procedure for manufacturing a packaging bag 200 (packaging body) using the laminate 100 is described below. A pair of laminates 100 is prepared. In the case of the laminate 100, the sealant layers 30 of the laminates 100 are placed opposite each other, and the sealant layers 30 are bonded together with, for example, a fastener tape interposed therebetween, which serves as the resealing means 230. This forms sealed portions 211 at positions corresponding to the upper end 217 and the side ends 214, 214, and forms a non-sealed portion 215 surrounded by the sealed portions 211 in a U-shape.

[0045] After the sealing portion 211 is formed, the opening means 220 may be formed. For example, the side end portions 214, 214 are formed with easy-to-open processed portions 224, 224 consisting of a group of scars. The easy-to-open processed portions 224 are not limited to a group of scars, and may be V-shaped, U-shaped, I-shaped or other notches. In addition, a half-cut line 221 that serves as a trajectory for cutting from the easy-to-open processed portion 224 may be formed on the surface portion of the laminate 100 between the upper end portion 217 and the resealing means 230. The half-cut line 221 can be formed using a laser beam. After the opening means 220 is formed, the sealing portion 211 is cut and trimmed to separate the package into individual packaging bags.

[0046] Next, the contents are filled from the unsealed lower end 216. Thereafter, the laminates 100 are bonded together at the lower end 216, and a seal portion 211 is also formed at the lower end 216. In this manner, the packaging bag 200 and the package can be manufactured. The half-cut line may be formed before the pair of laminates 100 that have been bonded together are slit to a predetermined width.

[0047] The packaging bag 200 is provided with opening means 220 at the upper end side of the non-sealed portion 215 for cutting open the side ends 214, 214 of the packaging bag 200 and across the space therebetween to open the bag, and resealing means 230 below the opening means 220 for resealing the storage portion 218 after the bag is opened by the opening means 220. The resealing means 230 may appropriately adopt a known structure capable of repeatedly opening and sealing. For example, the resealing means 230 may be a synthetic resin fastener capable of repeatedly sealing by fitting a strip-shaped protrusion into a strip-shaped groove, or may be an adhesive seal.

[0048] The package includes a packaging bag 200 and an object contained in a container 218 of the packaging bag 200. Examples of the object include food, electronic materials, and electronic devices. The package includes the packaging bag 200, and therefore has high puncture strength, and can prevent the object from being altered or deteriorated due to intrusion of trace components, PET components, or outside air through a through hole created by puncture. In addition, recycled PET can be used as the packaging bag, so that an environmentally friendly package with improved puncture strength can be provided.

[0049] Although several embodiments of the present disclosure have been described above, the present disclosure is not limited to the above embodiments. For example, the laminate 100 and the laminate 101 used in the above description may be appropriately replaced with each other. The laminates 100 and 101 may have any layer or thin film between the base film 10 and the sealant layer 30, between the base film 10 and the intermediate layer 20, or between the intermediate layer 20 and the sealant layer 30, as long as the function of the laminate is not significantly impaired. The shape of the packaging bag 200 and the packaging body is not limited to a four-sided bag. For example, it may be a two-sided bag, a three-sided bag, or a palm-shaped bag, or it may be a standing pouch shape with a bottom tape added.

[0050] The present disclosure includes the following embodiments. [1] A polyester film as a base film and a sealant layer, The average birefringence of the polyester film is 0.02 or more. [2] The laminate according to [1], wherein the average birefringence is 0.05 or less. [3] The laminate according to [1] or [2], wherein the polyester film comprises a mechanically recycled polyethylene terephthalate film. [4] The laminate according to [3], wherein the absolute value of the orientation angle of the mechanically recycled polyethylene terephthalate film is 80° or less. [5] The laminate according to any one of [1] to [4], wherein the base film has a thickness of 9 to 100 μm. [6] The laminate according to any one of [1] to [5], wherein the base film has a puncture strength of 7.0 N or more. [7] The laminate according to any one of [1] to [6], wherein the average orientation angle of the base film is 80° or less. [8] A packaging bag comprising the laminate according to any one of the above [1] to [7]. [9] A packaging body comprising the packaging bag described in [8] above and an item contained in the storage section of the packaging bag. EXAMPLES

[0051] The present disclosure will be described in more detail below with reference to examples and comparative examples. Note that the present disclosure is not limited to the following examples.

[0052] (Examples 1 to 9, Comparative Example 1) [Preparation of polyethylene terephthalate (PET) film] A commercially available mechanically recycled PET film (MR-PET film) and a commercially available PET film (general PET film) that had not been recycled were prepared. Hereinafter, the term "PET film" refers to both MR-PET film and general film. The thickness of each PET film was 12 μm. All of the PET films used were produced by biaxial stretching, and the films were stretched in the MD direction and then in the TD direction.

[0053] [Preparation of the base film] Each PET film was cut into five pieces along the first virtual line VL1 and the second virtual line VL2 as shown in FIG. 2. The five cut films were identified by position numbers #1, #2, #3, #4, and #5 from left to right. By changing the cutting positions in this way, a plurality of base films (cut films) with different degrees of stretching were prepared. The cut films obtained by cutting the MR-PET film were designated as Examples 1 to 4 and Comparative Example 1, and the cut films obtained by cutting the general PET film were designated as Examples 5 to 9.

[0054] [Measurement of birefringence and orientation angle of a piece of PET film] Each of the cut-out base films was further cut to obtain a 4.0 cm x 4.0 cm film piece. The birefringence and orientation angle of the obtained film piece were measured under the following conditions using a retardation measuring device (product name: KOBRA-WR, manufactured by Oji Scientific Instruments Co., Ltd.). The birefringence and orientation angle were measured simultaneously. Ten film pieces were cut out from each base film, and the birefringence (Δn) and orientation angle of each film piece were measured according to the formula (1) under the following conditions. ·Measurement method: In-plane phase difference measurement ·Measurement method: standard ·Order: automatic ·Orientation angle display range: -90°~90° Thickness input: Yes (for example, if you are measuring a PET film with a thickness of 12 μm, enter the thickness as 12 μm) ·Measurement area: 5mm diameter Birefringence = nx-ny (1)

[0055] From the measured values ​​of the birefringence of the film pieces, the average value and relative standard deviation of the birefringence of the base film were calculated for each position number. Base film having an average value of birefringence of 0.02 or more was used as an example, and base film having an average value of birefringence of less than 0.02 was used as a comparative example. The results of the MR-PET film are shown in Table 1, and the results of the general PET film are shown in Table 2. FIG. 5 is a graph in which the measurement results and average values ​​of the birefringence of the film pieces of each base film obtained from the MR-PET film are plotted for each position number. FIG. 8 is a graph in which the measurement results and average values ​​of the birefringence of the film pieces of each base film obtained from the general PET film are plotted for each position number.

[0056] When the measured value of the orientation angle was a negative value, the absolute value was taken as the orientation angle. The average value and relative standard deviation of the orientation angle of the substrate film were calculated for each position number using the same procedure as for the measurement of birefringence. The results for the MR-PET film are shown in Table 1, and the results for the general PET film are shown in Table 2. The values ​​shown in parentheses in Tables 1 and 2 indicate that the measured value was a negative value. For example, the entry (89.86) in Tables 1 and 2 indicates that the measured value was -89.86. Figure 6 is a graph in which the measurement results and average values ​​of the orientation angles of the film pieces of each substrate film obtained from the MR-PET film are plotted for each position number. Figure 7 is a graph in which the measurement results and average values ​​of the orientation angles of the film pieces of each substrate film obtained from the general PET film are plotted for each position number.

[0057] [PET film puncture strength measurement] As in the measurement of birefringence and orientation angle, the cut-out substrate film at each position number was cut to obtain 10 pieces of film of 5.0 m x 5.0 cm each. The puncture strength of each film piece was measured under the following conditions based on "7.5 Puncture Strength Test" of JIS Z1707:2019 "General Rules for Food Packaging Plastic Films". The measurement device used was Tensilon AD-7703 (manufactured by A & D Co., Ltd.). The average value and relative standard deviation of the puncture strength of the substrate film were calculated for each position number using the same procedure as in the measurement of birefringence. The results of the MR-PET film are shown in Table 1, and the results of the general PET film are shown in Table 2. In addition, Figure 7 is a graph in which the measurement results and average values ​​of the puncture strength of each substrate film obtained from the MR-PET film are plotted for each position number. Figure 10 is a graph in which the measurement results and average values ​​of the puncture strength of each substrate film obtained from the general PET film are plotted for each position number.

[0058] Test speed: 50mm / min Load cell: 100N Load range: 10N (10%)

[0059] [Table 1]

[0060] [Table 2]

[0061] As shown in Tables 1 and 2, the MR-PET film had a smaller average puncture strength than the general PET film. Furthermore, as shown in Table 1, Figures 5 and 7, the average birefringence and average puncture strength of the MR-PET film were the lowest for the substrate film at position number #3. Furthermore, as shown in Figures 5 and 7, a positive correlation was observed between the average birefringence and the average puncture strength of the MR-PET film. Therefore, it was found that a substrate film having high puncture strength can be obtained by selecting a substrate film having a high birefringence. A film having such a high birefringence can be obtained, for example, by cutting out a portion of the original film close to the end along the stretching direction. Furthermore, by using such a film as a substrate film in a laminate, a laminate having high puncture strength can be obtained.

[0062] Furthermore, comparing Figures 7 and 10, the MR-PET film had a larger variation in puncture strength in the TD direction than the general PET film. This confirmed that using birefringence as an index is more useful for the MR-PET film than for the general PET film. In addition, as shown in Figures 5 and 6, as well as Figures 8 and 9, there was a tendency for a negative correlation to exist between the birefringence and the orientation angle. Therefore, it is believed that the birefringence and orientation angle were affected by the change in the molecular orientation of the film due to stretching, and that this in turn caused the puncture strength to change. [Industrial Applicability]

[0063] According to the present disclosure, it is possible to provide a laminate having sufficiently high puncture strength, as well as a packaging bag and a packaging body including such a laminate. [Explanation of symbols]

[0064] 10...base film, 11...cut film, 20...intermediate layer, 30...sealant layer, 40...metal layer, 100, 101...laminate, S...adhesive layer, 105...stretched film, #1, #2, #3, #4, #5...position number, VL1...first virtual line, VL2...second virtual line, 200...packaging bag, 211...sealed portion, 214...side end, 215...non-sealed portion, 216...lower end, 217...upper end, 218...container, 220...opening means, 221...half-cut line, 224...easy-open processing portion, 230...resealing means.

Claims

1. The film includes a polyester film as a base film and a sealant layer, The average birefringence of the polyester film is 0.02 or more.

2. The laminate according to claim 1 , wherein the average value of the birefringence is 0.05 or less.

3. The laminate according to claim 1 or 2, wherein the polyester film comprises a mechanically recycled polyethylene terephthalate film.

4. The laminate according to claim 3, wherein the absolute value of the orientation angle of the mechanically recycled polyethylene terephthalate film is 80° or less.

5. The laminate according to claim 1 or 2, wherein the thickness of the substrate film is 9 to 100 μm.

6. The laminate according to claim 1 or 2, wherein the substrate film has a puncture strength of 7.0 N or more.

7. The laminate according to claim 1 or 2, wherein the average orientation angle of the base film is 80° or less.

8. A packaging bag comprising the laminate according to claim 1 or 2.

9. A package comprising the packaging bag according to claim 8 and an item contained in the container of the packaging bag.

Images