bag

Abstract

To provide a bag making it possible to release steam to the outside through a part of a laminate strength adjustment layer which is peeled off due to heat.SOLUTION: A bag includes: an outer edge sealing part that is extended along an outer edge of the bag and connects inner surfaces of a bag material together; and a butt-seam sealing part to connect an inner surface of an upper surface film and an inner surface of a lower surface film at a butt-seam part where the upper surface film is overlapped with the lower surface film. A laminate strength adjustment layer is disposed so as to be overlapped at least partially with the butt-seam part.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a bag having a packaging material that includes a laminate strength adjusting layer partially positioned between a substrate and a sealant layer. [Background technology]

[0002] Conventionally, many products on the market contain contents housed in containers made of laminated plastic. In these containers, the non-sealed sections, where the laminated layers are not joined, constitute the storage area where the contents are held. The sealed sections, where the laminated layers are joined, seal the storage area. The contents are stored in the container, for example, in a frozen state. The contents are then heated in the container using a microwave oven or similar device.

[0003] Incidentally, when contents contained in a sealed container are heated using a microwave oven, the water contained in the contents evaporates as heating occurs, increasing the pressure inside the container. When the pressure inside the container rises, there is a risk that the container may burst, scattering the contents and contaminating the inside of the microwave oven. Considering this problem, for example, Patent Document 1 proposes a mechanism that automatically connects the container to the outside when the pressure inside the container rises, thereby releasing the steam inside the container to the outside. The mechanism disclosed in Patent Document 1 includes a laminate strength adjustment layer located between the base material layer and the thermoplastic resin layer. The laminate strength adjustment layer is a layer that has the property of decreasing in strength at high ambient temperatures. By providing such a layer, steam can be released to the outside of the container through the portion of the laminate strength adjustment layer that has peeled off due to heat. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2008-1394 [Overview of the project] [Problems that the invention aims to solve]

[0005] The present invention aims to provide a bag comprising a laminate strength adjustment layer that is positioned to at least partially overlap the gusseted seal portion. [Means for solving the problem]

[0006] The present invention relates to a bag having a front and back surface formed from a packaging material, The packaging material has at least a base material and a sealant layer, arranged in order from the outer side to the inner side. The substrate includes at least one biaxially oriented plastic film, The sealant layer contains polyethylene as its main component, The packaging material constituting the surface includes an upper surface film located at least at the top of the bag, and a lower surface film located at least at the bottom of the bag and partially overlapping with the upper surface film. At least one of the packaging material constituting the upper surface film and the packaging material constituting the lower surface film further comprises a laminate strength adjusting layer partially located between the substrate and the sealant layer. The aforementioned bag is The bag comprises an outer edge sealing portion that extends along the outer edge and joins the inner surfaces of the packaging materials together, and a gusset sealing portion that joins the inner surface of the upper surface film and the inner surface of the lower surface film in the gusset portion where the upper surface film and the lower surface film are overlapped, The laminate strength adjustment layer is positioned so as to at least partially overlap the gable seal portion of the bag.

[0007] In the bag according to the present invention, the gusset seal portion includes a tip seal portion extending along the tip of the gusset portion and a steam vent seal portion protruding from the tip seal portion toward the base of the gusset portion. The aforementioned gable portion has an unsealed portion that is isolated from the storage portion of the bag by the steam venting seal portion. The laminate strength adjustment layer may be arranged so as to at least partially overlap the steam vent seal portion.

[0008] In the bag according to the present invention, the laminate strength adjustment layer may spread from the inner edge to the outer edge of the steam vent seal portion.

[0009] The bag according to the present invention may include a through portion that penetrates the packaging material in the non-sealed portion that is separated from the accommodating portion of the bag by the steam vent seal portion.

[0010] In the bag according to the present invention, the non-sealed portion that is separated from the accommodating portion of the bag by the steam vent seal portion may spread to the tip of the clasp portion.

[0011] The bag according to the present invention includes a through portion that penetrates the packaging material in the clasp seal portion, and the laminate strength adjustment layer may spread from the inner edge of the clasp seal portion to the through portion.

[0012] The bag according to the present invention may include a lower film that is located between the lower surface film and the back film and constitutes the lower part of the bag.

[0013] The bag according to the present invention may include an easy-opening means formed at the side edge of the bag between the clasp portion and the lower film.

[0014] In the bag according to the present invention, there may be only two biaxially stretched plastic films included in the base material.

[0015] In the bag according to the present invention, the two biaxially stretched plastic films may contain polyester as a main component.

[0016] In the bag according to the present invention, one of the two biaxially oriented plastic films may contain polyester as its main component, and the other of the two biaxially oriented plastic films may contain polyamide as its main component.

[0017] In the bag according to the present invention, there is only one biaxially oriented plastic film contained in the base material. The biaxially oriented plastic film may contain polyester as its main component.

[0018] In the bag according to the present invention, there is only one biaxially oriented plastic film contained in the base material. The biaxially oriented plastic film may contain polyamide as its main component.

[0019] In the bag according to the present invention, the polyethylene in the sealant layer may include low-density polyethylene, and / or linear low-density polyethylene in which the α-olefin is butene.

[0020] In the bag according to the present invention, the laminate strength adjusting layer may be composed of a resin composition comprising polyamide, cellulose, and an ethylene-vinyl acetate copolymer resin or polyolefin wax. [Effects of the Invention]

[0021] According to the present invention, steam can be released to the outside of the bag through the portion of the laminate strength adjustment layer that has been peeled off by heat. [Brief explanation of the drawing]

[0022] [Figure 1] This is a front view showing an example of a bag according to an embodiment of the present invention. [Figure 2] Figure 1 is an exploded view showing the film that makes up the bag. [Figure 3] This is a front view showing the bag with the top sealed. [Figure 4]This is a cross-sectional view along line IV-IV of the bag in Figure 3. [Figure 5] This is a cross-sectional view showing an example of the layer structure of packaging material. [Figure 6] This is a cross-sectional view showing an example of the layer structure of packaging material. [Figure 7] This is a cross-sectional view showing an example of the layer structure of packaging material. [Figure 8] This is a cross-sectional view showing an example of the layer structure of packaging material. [Figure 9] This is a cross-sectional view showing an example of the layer structure of packaging material. [Figure 10] This is a cross-sectional view showing an example of the layer structure of packaging material. [Figure 11] This is a cross-sectional view showing an example of the layer structure of packaging material. [Figure 12] This is a cross-sectional view showing an example of the layer structure of packaging material. [Figure 13] This is a plan view showing an example of a loop stiffness measuring instrument. [Figure 14] Figure 13 is a cross-sectional view of the loop stiffness measuring instrument along line XIV-XIV. [Figure 15] This is a diagram illustrating the process of attaching a test specimen to a loop stiffness measuring instrument. [Figure 16] This is a diagram illustrating the process of forming a loop portion on a test specimen. [Figure 17] This is a diagram illustrating the process of applying a load to the loop portion of the test specimen. [Figure 18] This is a diagram illustrating the process of applying a load to the loop portion of the test specimen. [Figure 19] This is a cross-sectional view showing an example of a test specimen for measuring the lamination strength of the first region of a packaging material. [Figure 20] This is a cross-sectional view showing an example of a test specimen for measuring the lamination strength of the first region of a packaging material. [Figure 21] This is a cross-sectional view showing an example of a test specimen for measuring the lamination strength of the second region of a packaging material. [Figure 22] This figure shows an example of a method for measuring laminate strength. [Figure 23] This figure shows an example of the change in tensile stress with respect to the distance between a pair of grips during the process of measuring the laminate strength of the test specimen shown in Figure 20. [Figure 24] This figure shows an example of the change in tensile stress with respect to the distance between a pair of grips during the process of measuring the laminate strength of the test specimen shown in Figure 21. [Figure 25] Figure 1 is an exploded view showing a modified example of the film that makes up the bag shown. [Figure 26] Figure 25 is a cross-sectional view showing a bag made of the film shown. [Figure 27] This is a front view showing one modified version of the bag. [Figure 28] This is a cross-sectional view of the bag along line XXVIII-XXVIII in Figure 27. [Figure 29] This is a front view showing an example of a bag. [Figure 30] Figure 29 is a cross-sectional view along the line XXX-XXX of the bag. [Figure 31] This is a front view showing one modified example of the packaging. [Figure 32] This is a front view showing one modified example of the packaging. [Figure 33] This is a front view showing one modified example of the packaging. [Figure 34] This figure shows the evaluation results of the examples and comparative examples. [Figure 35] This figure shows the evaluation results of the examples and comparative examples. [Modes for carrying out the invention]

[0023] Embodiments of the present invention will be described with reference to Figures 1 to 24. Note that, for the sake of illustration and ease of understanding, the scale and aspect ratios of the drawings attached to this specification have been appropriately modified and exaggerated from those of the actual objects.

[0024] Furthermore, terms such as "parallel," "orthogonal," and "identical," as well as values ​​for length and angle, used in this specification to specify shapes, geometric conditions, and their degrees, shall not be strictly interpreted, but shall be interpreted to include a range that allows for the expectation of similar functionality.

[0025] bag Figure 1 is a front view showing the bag 10 according to this embodiment. Figure 2 is an exploded view showing the film that constitutes the bag shown in Figure 1. The bag 10 includes a storage section 17 for containing contents. Note that Figure 1 shows the bag 10 without any contents inside. The configuration of the bag 10 will be described below.

[0026] In this embodiment, the bag 10 is a gusset-type bag configured to be self-supporting. The bag 10 includes an upper part 11, a lower part 12, and side parts 13, and has a substantially rectangular outline in the front view. The names such as "upper part," "lower part," and "side parts," as well as terms such as "upper" and "downward," merely describe the relative position and orientation of the bag 10 and its components based on the state in which the bag 10 is self-supporting with the gusset part facing downwards. The posture of the bag 10 during transport or use is not limited by the names and terms used herein.

[0027] The bag 10 comprises a surface film that constitutes the surface, a back film 15 that constitutes the back surface, and a bottom film 16 that constitutes the bottom 12. The surface film 14 includes an upper surface film 141 located at least on the upper part 11 of the bag 10, and a lower surface film 142 located at least on the bottom part 12 of the bag 10. The upper surface film 141 and the lower surface film 142 are partially overlapped. Specifically, the inner surface of the lower tip portion of the upper surface film 141 and the inner surface of the upper tip portion of the lower surface film 142 are overlapped and joined to each other. In the following description, the portion where the upper surface film 141 and the lower surface film 142 are overlapped will also be referred to as the girdle portion 20. Furthermore, the end of the girdle portion 20 that is on the side of the storage portion 17 will also be referred to as the base portion 201, and the end located on the opposite side of the base portion 201 will also be referred to as the tip portion 202.

[0028] Each film constituting the bag 10 is made of a packaging material comprising a base material including at least one biaxially oriented plastic film and a sealant layer mainly composed of polyethylene. Furthermore, at least one of each film, either the upper surface film 141 or the lower surface film 142, is made of a packaging material 30 described later, which has a laminate strength adjustment layer 35 partially located between the base material and the sealant layer. In this embodiment, the lower surface film 142 is made of a packaging material 30 having a laminate strength adjustment layer 35 partially located between the base material and the sealant layer. The lower film 16 is folded over at the folded portion 16f and positioned between the lower surface film 142 and the back film 15.

[0029] It should be noted that the terms "upper surface film," "lower surface film," "surface film," "backside film," and "bottom film" mentioned above are merely ways of dividing the films according to their relative positions, and the method of providing the films when manufacturing the bag 10 is not limited by these terms. For example, as will be described later, the bag 10 may be manufactured using a total of three films: one film in which the upper surface film 141 and the lower surface film 142 are connected, one backside film 15, and one bottom film 16. Alternatively, the lower surface film 142 and the bottom film 16 may be connected, or the backside film 15 and the bottom film 16 may be connected.

[0030] The upper surface film 141, the lower surface film 142, the back film 15, and the lower film 16 are joined together on their inner surfaces by a sealing portion. In the front view of the bag 10, such as in Figure 1, hatching is applied to the sealing portion.

[0031] As shown in Figure 1, the sealing portion has an outer edge sealing portion that extends along the outer edge of the bag 10 when viewed from the surface film 14 side. The outer edge sealing portion includes a lower sealing portion 12a that extends to the lower part 12, and a pair of side sealing portions 13a that extend along the pair of side portions 13. In the state before contents are filled (when the bag 10 does not contain contents), as shown in Figure 1, the upper part 11 of the bag 10 is an opening 11b.

[0032] Figure 3 shows a bag 10 with contents 19 inside and the top 11 sealed. After the contents 19 are placed inside the bag 10, the inner surface of the upper surface film 141 and the inner surface of the back film 15 are joined at the top 11 to form the upper seal portion 11a and seal the bag 10.

[0033] The side sealing portion 13a and the upper sealing portion 11a are sealing portions formed by joining the inner surface of the upper surface film 141 or the inner surface of the lower surface film 142 to the inner surface of the back surface film 15. On the other hand, the lower sealing portion 12a is a sealing portion formed by joining the inner surface of the lower surface film 142 to the inner surface of the lower film 16, or the inner surface of the back surface film 15 to the inner surface of the lower film 16.

[0034] Furthermore, the sealing portion of the bag 10 has a gusset sealing portion 21 that joins the inner surface of the upper surface film 141 and the inner surface of the lower surface film 142 in the gusset portion 20 where the upper surface film 141 and the lower surface film 142 are overlapped. As shown in Figures 1 and 3, the gusset sealing portion 21 includes at least a tip sealing portion 21a that extends along the tip portion 202 of the gusset portion 20 from one side sealing portion 13a to the other side sealing portion 13a.

[0035] The method for forming the seal is not particularly limited, as long as the opposing films can be joined together to seal the bag 10. For example, the seal may be formed by melting the inner surfaces of the films by heating and welding the inner surfaces together, i.e., by heat sealing. Alternatively, the seal may be formed by bonding the inner surfaces of the opposing films together using an adhesive or the like.

[0036] In the following description, the direction in which the pair of side portions 13 face each other will also be referred to as the first direction D1, and the direction perpendicular to the first direction D1 will also be referred to as the second direction D2. The first direction D1 is the transport direction of the packaging material 30 when making the bag 10 from each film 14, 15, and 16, and is the so-called MD (Machine Direction). The second direction D2 is the so-called TD (Transverse Direction). In the examples shown in Figures 1 and 3, the upper part 11, lower part 12, and gusset portion 20 extend along the first direction D1, and the side portions 13 extend along the second direction D2.

[0037] The contents 19 are, for example, cooked or partially cooked food. Examples of food include frozen foods, prepared foods, and snacks. However, the contents 19 are not limited to these.

[0038] Examples of frozen foods include frozen noodles (frozen pasta, frozen yakisoba, frozen udon, frozen ramen, frozen vermicelli, etc.), frozen prepared foods (for example, frozen hijiki seaweed stew, frozen dried daikon radish stew, frozen meat and potato stew, frozen simmered butterbur, frozen Chikuzen-ni (a type of Japanese stew), frozen blanched vegetables, frozen sesame-dressed vegetables, etc.), and frozen rice dishes (frozen fried rice, frozen pilaf, frozen chicken rice, frozen dry curry, frozen rice with sauce, frozen fried rice with sauce, frozen porridge, etc.).

[0039] Examples of prepared foods include takoyaki, french fries, fried chicken, steamed buns, hamburgers, meatballs, minced meat cutlets, croquettes, chicken nuggets, shumai, gyoza, sausages, tonkatsu, karaage, meatballs, tempura, and edamame.

[0040] Snack foods include rice crackers such as senbei and arare, direct puff snacks, potato chips, corn chips, nuts, pretzels, and popcorn, all of which are made primarily from starchy agricultural products such as potatoes, wheat flour, corn, and rice. Note that snack foods made from these ingredients may or may not be deep-fried.

[0041] The intended use of bag 10 is heating, such as in a microwave oven. Bag 10 is equipped with a steam release mechanism 25 to release steam generated from the contents during heating. The steam release mechanism 25 is configured to release steam by connecting the inside and outside of bag 10 when the moisture contained in the contents 19 evaporates during heating and the pressure in the storage compartment exceeds a predetermined value.

[0042] Furthermore, when heating the bag 10 equipped with the steam venting mechanism 25 using a microwave oven or the like, the pressure in the containment compartment may not rise to a level sufficient to allow steam to escape from the steam venting mechanism 25. In other words, depending on how the bag 10 is used, the probability of the steam venting mechanism 25 functioning to release steam to the outside may be low. Even in this case, by providing the steam venting mechanism 25 in the bag 10, the probability of steam escaping from locations other than the steam venting mechanism 25 or the bag 10 bursting can be further reduced.

[0043] In this embodiment, the steam venting mechanism 25 is provided in the gable portion 20. The gable portion 20 will be described in detail below. Figure 4 is a cross-sectional view of the bag 10 in Figure 3 along line IV-IV. In this embodiment, the gable portion 20 includes a steam venting seal portion 21b that protrudes from the tip seal portion 21a toward the base portion 201. The gable portion 20 also has an unsealed portion 23 that is isolated from the containment portion 17 by the steam venting seal portion 21b. The steam venting seal portion 21b and the unsealed portion 23 may be located in the center of the gable portion 20 in the first direction D1.

[0044] An "unsealed portion" is a part where the inner surface of one packaging material and the inner surface of another packaging material face each other, but their inner surfaces are not joined together. In the unsealed portion 23, the inner surface of the upper surface film 141 and the inner surface of the lower surface film 142 face each other, but their inner surfaces are not joined together. "Isolation" means that the containment portion 17 and the unsealed portion 23 are not in communication with each other. In this embodiment, the unsealed portion 23 is surrounded by the tip seal portion 21a and the steam vent seal portion 21b.

[0045] Furthermore, the girder portion 20 has a through portion 22 that penetrates at least one of the upper surface film 141 or the lower surface film 142 in the non-seal portion 23. The through portion 22 may penetrate both the upper surface film 141 and the lower surface film 142. The through portion 22 may be a notch or a hole, as shown in Figures 1 and 3. The notch constituting the through portion 22 may have a shape that is convex toward the base portion 201, as shown in Figures 1 and 3.

[0046] When the contents are heated using a microwave oven, the moisture evaporates and the pressure in the storage section 17 increases, causing the steam vent seal section 21b to peel off, creating communication between the storage section 17 and the unsealed section 23. Steam that flows from the storage section 17 to the unsealed section 23 through the peeled portion of the steam vent seal section 21b escapes to the outside of the bag 10 through the penetration section 22. In this way, the steam vent seal section 21b, the unsealed section 23, and the penetration section 22 can function as a steam venting mechanism 25 that connects the inside and outside of the bag 10 to release steam when the pressure in the storage section 17 exceeds a predetermined value.

[0047] The girder portion 20 may further have an unseal portion 26 that is isolated from the unseal portion 23 and the housing portion 17. The unseal portion 26 is located, for example, between the steam vent seal portion 21b and the side portion 13 in a first direction D1. Multiple unseal portions 26 may be lined up in the first direction D1. Also, a through portion 27 may be formed in the unseal portion 26. For example, among the multiple unseal portions 26 located between the steam vent seal portion 21b and the side portion 13, the through portion 27 may be formed in the unseal portion 26 that is closest to the steam vent seal portion 21b.

[0048] Furthermore, in this embodiment, the steam venting mechanism 25 includes a laminate strength adjustment layer 35 that is partially disposed between multiple layers constituting the packaging material 30 of the lower surface film 142. The laminate strength adjustment layer 35 is disposed in the portion of the lower surface film 142 that constitutes the girth portion 20. Specifically, as shown in Figure 2, the laminate strength adjustment layer 35 is disposed in the center of the upper end of the lower surface film 142. Also, as shown in Figures 1, 3, and 4, the laminate strength adjustment layer 35 is disposed so as to at least partially overlap the steam venting seal portion 21b of the girth portion seal portion 21 formed on the girth portion 20. The laminate strength adjustment layer 35 may extend to overlap both the steam venting seal portion 21b and the tip seal portion 21a of the girth portion seal portion 21.

[0049] The laminate strength adjustment layer 35 is a layer that has the property of decreasing in strength at high ambient temperatures. The laminate strength adjustment layer 35 may have a predetermined strength at ambient temperatures below room temperature. Ambient temperatures below room temperature typically refer to the ambient temperature during the packaging process in which the contents are packaged, the ambient temperature during the process of refrigerating or freezing the bags containing the contents, and the ambient temperature during the distribution stage when the contents are transported or stored in a refrigerated or frozen state. The materials that make up such a laminate strength adjustment layer 35 will be described later.

[0050] As shown in Figures 3 and 4, the laminate strength adjustment layer 35 may extend across the steam vent seal portion 21b and the containment portion 17 of the girdle portion 20 in the packaging material 30 of the lower surface film 142. Alternatively, the laminate strength adjustment layer 35 may extend from the inner edge (the edge on the containment portion side) to the outer edge (the edge on the external environment side) of the steam vent seal portion 21b. This allows for the formation of a steam flow path from the inner edge (the edge on the containment portion side) to the outer edge (the edge on the external environment side) of the steam vent seal portion 21b if peeling of the laminate strength adjustment layer 35 occurs due to heating. The laminate strength adjustment layer 35 may extend in the first direction D1 in the girdle portion 20 so as not to reach the portion of the girdle portion seal portion 21 that surrounds the non-sealed portion 26.

[0051] As shown in Figures 1 and 4, the dimensions of the laminate strength adjustment layer 35 in the first direction D1, which is the direction in which the rafter portion 20 extends, may be larger than the dimensions of the laminate strength adjustment layer 35 in the second direction D2. Alternatively, although not shown, the dimensions of the laminate strength adjustment layer 35 in the first direction D1 may be smaller than the dimensions of the laminate strength adjustment layer 35 in the second direction D2.

[0052] In the following description, the region of the packaging material 30 that includes the laminate strength adjustment layer 35 will also be referred to as the first region 33. The region of the packaging material 30 that does not include the laminate strength adjustment layer 35 will also be referred to as the second region 34.

[0053] Easy-to-open means The bag 10 may be equipped with an easy-opening means 28 for opening the bag 10 by tearing the packaging material that constitutes the bag 10. For example, as shown in Figures 1 and 3, the easy-opening means 28 may include a notch 29 formed in the side seal portion 13a that serves as the starting point for tearing. In addition, the easy-opening means 28 may be provided in the part that serves as the path when tearing the bag 10, such as a half-cut line formed by laser processing or a cutter.

[0054] The easy-opening means 28 may be formed on only one of the pair of side sealing portions 13a, or on both of the pair of side sealing portions 13a. Alternatively, the easy-opening means 28 may be formed on the side sealing portion 13a between the girdle portion 20 and the lower portion 12.

[0055] Furthermore, although not shown in the figures, the easy-open means 28 may also include notches or groups of scratches formed in the side sealing portion 13a. The group of scratches may include, for example, a plurality of through holes formed to penetrate the surface film 14 and / or back film 15. Alternatively, the group of scratches may include a plurality of holes formed on the outer surface of the surface film 14 and / or back film 15 so as not to penetrate the surface film 14 and / or back film 15.

[0056] Other configurations Notches may be formed in the portion of the lower film 16 that overlaps with the lower surface film 142 and the back film 15. In the example shown in Figure 1, semicircular notches are formed in the portions of the lower film 16 that constitute a pair of side edges of the bag 10. In this case, at the positions where the notches are formed in the lower film 16, the inner surface of the lower surface film 142 and the inner surface of the back film 15 can be joined to form a side seal portion 13a. This can improve the self-supporting ability of the bag 10.

[0057] packaging material (Packaging material for surface film) Next, the layer structure of the packaging material 30, which comprises the laminate strength adjustment layer 35 described above and constitutes the lower surface film 142, will be explained. Figure 5 is a cross-sectional view showing an example of the layer structure of the packaging material 30.

[0058] The packaging material 30 has an outer surface 31 and an inner surface 32. The inner surface 32 is the surface located on the side of the container, and the outer surface 31 is the surface located on the opposite side of the inner surface 32. As shown in Figure 5, the packaging material 30 comprises at least a base material 40 located on the side of the outer surface 31, a sealant layer 50 located on the side of the inner surface 32, and a laminate strength adjustment layer 35 located between the base material 40 and the sealant layer 50. In this application, not only the surface of the packaging material 30 but also the surfaces of each layer are referred to as the inner surface if they are located on the side of the container such as the bag 10, and the outer surface if they are located on the opposite side of the inner surface.

[0059] The substrate 40 has at least one biaxially oriented plastic film. In the example shown in Figure 5, the substrate 40 has a first biaxially oriented plastic film 41, a second biaxially oriented plastic film 42 located on the sealant layer 50 side of the first biaxially oriented plastic film 41, and an adhesive layer 43 located between the first biaxially oriented plastic film 41 and the second biaxially oriented plastic film 42. In the example shown in Figure 5, the packaging material 30 contains only two biaxially oriented plastic films: the first biaxially oriented plastic film 41 and the second biaxially oriented plastic film 42.

[0060] As shown in Figure 5, the packaging material 30 may further include a pattern layer 45 located between the first biaxially oriented plastic film 41 and the adhesive layer 43.

[0061] In the example shown in Figure 5, the sealant layer 50 is laminated by bonding a sealant film 51, which has been pre-formed using a method such as inflation, to a laminate strength adjustment layer on the second biaxially oriented plastic film 42 of the substrate 40 via an adhesive using a dry lamination method. In this case, an adhesive layer 61 made of adhesive exists between the substrate 40 and the sealant layer 50.

[0062] Figure 6 is a cross-sectional view showing another example of the layer structure of the packaging material 30. The packaging material 30 shown in Figure 6 is identical to the packaging material 30 shown in Figure 5, except that the method of laminating the sealant layer 50 is different.

[0063] In the example shown in Figure 6, the sealant layer 50 is laminated by applying an anchor coating agent to the second biaxially oriented plastic film 42 and the laminate strength adjustment layer 35 of the substrate 40, and then coating the materials constituting the sealant layer 50 using an extrusion coating method. In this case, an anchor coating layer 62 made of the anchor coating agent exists between the substrate 40 and the sealant layer 50.

[0064] Figure 7 is a cross-sectional view showing another example of the layer structure of the packaging material 30. The packaging material 30 shown in Figure 7 is identical to the packaging material 30 shown in Figure 5, except that the method of laminating the sealant layer 50 is different.

[0065] In the example shown in Figure 7, the sealant layer 50 is laminated by coating the material constituting the sealant layer 50 onto the second biaxially oriented plastic film 42 and the laminate strength adjustment layer 35 of the substrate 40 using an extrusion coating method. In this case, the sealant layer 50 is in contact with the inner surface of the second biaxially oriented plastic film 42 and the inner surface of the laminate strength adjustment layer 35 of the substrate 40.

[0066] Figure 8 is a cross-sectional view showing another example of the layer structure of the packaging material 30. The packaging material 30 shown in Figure 8 is identical to the packaging material 30 shown in Figure 5, except that the position of the pattern layer 45 is different.

[0067] As shown in Figure 8, the pattern layer 45 may be located between the second biaxially oriented plastic film 42 and the adhesive layer 43. Although not shown, in the packaging material 30 shown in Figure 6 and the packaging material 30 shown in Figure 7, the pattern layer 45 may also be located between the second biaxially oriented plastic film 42 and the adhesive layer 43.

[0068] Figure 9 is a cross-sectional view showing another example of the layer structure of the packaging material 30. The packaging material 30 shown in Figure 9 is identical to the packaging material 30 shown in Figure 5, except that the position of the pattern layer 45 is different.

[0069] As shown in Figure 9, the pattern layer 45 may be located between the second biaxially oriented plastic film 42 and the sealant layer 50. Although not shown, in the packaging material 30 shown in Figure 6 and the packaging material 30 shown in Figure 7, the pattern layer 45 may also be located between the second biaxially oriented plastic film 42 and the sealant layer 50.

[0070] As shown in Figures 5 to 9, when the packaging material 30 contains only two biaxially oriented plastic films, the thickness of the packaging material 30 may be, for example, 80 μm or more, 90 μm or more, 100 μm or more, or 105 μm or more. Alternatively, the thickness of the packaging material 30 may be 140 μm or less, 130 μm or less, 120 μm or less, 115 μm or less, or 110 μm or less.

[0071] The packaging material 30 may contain only one biaxially oriented plastic film. The packaging material 30 comprising only one biaxially oriented plastic film will be described below with reference to Figures 10 to 12.

[0072] Figure 10 is a cross-sectional view showing an example of the layer structure of the packaging material 30. The packaging material 30 comprises at least a base material 40 located on the outer surface 31 side and containing a biaxially oriented plastic film 44, a sealant layer 50 located on the inner surface 32 side, and a laminate strength adjustment layer 35 located between the base material 40 and the sealant layer 50. The packaging material 30 contains only one biaxially oriented plastic film.

[0073] As shown in Figure 10, the packaging material 30 may further include a pattern layer 45 located between the biaxially oriented plastic film 44 and the adhesive layer 43.

[0074] In the example shown in Figure 10, the sealant layer 50 is laminated by bonding a sealant film 51, which has been pre-formed using a method such as inflation, to a laminate strength adjustment layer on a biaxially oriented plastic film 44 of the substrate 40 via an adhesive using a dry lamination method. In this case, an adhesive layer 61 made of adhesive exists between the substrate 40 and the sealant layer 50.

[0075] Figure 11 is a cross-sectional view showing another example of the layer structure of the packaging material 30. The packaging material 30 shown in Figure 11 is identical to the packaging material 30 shown in Figure 10, except that the method of laminating the sealant layer 50 is different.

[0076] In the example shown in Figure 11, the sealant layer 50 is laminated by applying an anchor coating agent to the biaxially oriented plastic film 44 of the base material 40 and the laminate strength adjustment layer 35, and then coating the materials constituting the sealant layer 50 using an extrusion coating method. In this case, an anchor coating layer 62 made of the anchor coating agent exists between the base material 40 and the sealant layer 50.

[0077] Figure 12 is a cross-sectional view showing another example of the layer structure of the packaging material 30. The packaging material 30 shown in Figure 12 is identical to the packaging material 30 shown in Figure 10, except that the method of laminating the sealant layer 50 is different.

[0078] In the example shown in Figure 12, the sealant layer 50 is laminated by coating the material constituting the sealant layer 50 onto the biaxially oriented plastic film 44 of the substrate 40 and the laminate strength adjustment layer 35 using an extrusion coating method. In this case, the sealant layer 50 is in contact with the inner surface of the biaxially oriented plastic film 44 of the substrate 40 and the inner surface of the laminate strength adjustment layer 35.

[0079] As shown in Figures 10 to 12, when the packaging material 30 contains only one biaxially oriented plastic film, the thickness of the packaging material 30 is, for example, 60 μm or more, may be 70 μm or more, may be 80 μm or more, or may be 90 μm or more. Alternatively, the thickness of the packaging material 30 may be 120 μm or less, may be 110 μm or less, or may be 100 μm or less.

[0080] The following describes each layer that makes up the packaging material 30.

[0081] (base material) The biaxially oriented plastic films constituting the base material 40, such as the first biaxially oriented plastic film 41, the second biaxially oriented plastic film 42, and the biaxially oriented plastic film 44, are plastic films that have been stretched in two predetermined directions. The biaxially oriented plastic films are intentionally stretched to improve the mechanical strength of the plastic films. The stretching direction of each biaxially oriented plastic film 41, 42, and 44 is not particularly limited. For example, the biaxially oriented plastic films 41, 42, and 44 may be stretched in the first direction D1 and the second direction D2 described above. Also, the stretching directions of each biaxially oriented plastic film 41, 42, and 44 may be the same or different from each other. The stretching ratio of each biaxially oriented plastic film 41, 42, and 44 is, for example, 1.05 times or more.

[0082] The first biaxially oriented plastic film 41 and the second biaxially oriented plastic film 42 of the packaging material 30 shown in Figures 5 to 9 will be described in detail. Both the first biaxially oriented plastic film 41 and the second biaxially oriented plastic film 42 may be polyester films containing polyester as the main component. In the following description, a biaxially oriented plastic film containing polyester as the main component will also be referred to as a biaxially oriented polyester film. In this application, "main component" refers to the component that accounts for 51% by mass.

[0083] Biaxially oriented polyester films contain, for example, 51% by mass or more of polyester. Preferably, the polyester is an aromatic polyester composed mainly 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 (hereinafter also referred to as PET) and polybutylene terephthalate (hereinafter also referred to as PBT). In the following description, a biaxially oriented polyester film containing 51% by mass or more of PET will also be referred to as a biaxially oriented PET film. Similarly, a biaxially oriented polyester film containing 51% by mass or more of PBT will also be referred to as a biaxially oriented PBT film. The 51% by mass or more of polyester in the biaxially oriented polyester film may consist of one type of polyester or two or more types of polyester.

[0084] The thickness of the biaxially oriented polyester film is preferably 9 μm or more, and more preferably 12 μm or more. Furthermore, the thickness of the biaxially oriented polyester film is preferably 25 μm or less, and 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 gains sufficient strength. Furthermore, by making the thickness of the biaxially oriented polyester film 25 μm or less, the biaxially oriented polyester film exhibits excellent moldability. Therefore, the process of processing the packaging material 30 to manufacture the bag 10 can be carried out efficiently.

[0085] The thickness of a biaxially oriented polyester film is calculated by randomly measuring the thickness at 10 points on a cross-sectional photograph of the biaxially oriented polyester film taken using an optical microscope, and then determining the arithmetic mean of the measured thicknesses. The thickness of other films and layers, as well as the overall thickness of the packaging material 30, are calculated using the same method.

[0086] A biaxially oriented polyester film may have a loop stiffness of 0.0017 N or more in at least one direction. In the following description, a biaxially oriented polyester film having a loop stiffness of 0.0017 N or more in at least one direction and containing polyester as the main 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 flow direction (MD) or the perpendicular direction (TD). A high-stiffness polyester film may have a loop stiffness of 0.0017 N or more in both the flow direction (MD) and the perpendicular direction (TD). By including a high-stiffness polyester film in the packaging material 30, the packaging material 30 can have excellent puncture strength. A high-stiffness polyester film does not contain polyamide.

[0087] The thickness of the high-stiffness polyester film is preferably 5 μm or more, and more preferably 7 μm or more. Furthermore, the thickness of the high-stiffness polyester film is preferably 25 μm or less, and more preferably 20 μm or less.

[0088] Loop stiffness is a parameter that represents the stiffness of a film, such as a biaxially oriented plastic film. The method for measuring loop stiffness will be explained below with reference to Figures 13 to 18. The measurement method described below can be used not only for single-layer films such as biaxially oriented plastic films, but also for multi-layer films 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 oriented 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 the packaging material 30.

[0089] Figure 13 is a plan view showing the test specimen 80 and the loop stiffness measuring instrument 85, and Figure 14 is a cross-sectional view of the test specimen 80 and the loop stiffness measuring instrument 85 in Figure 13 along line XIV-XIV. The test specimen 80 is a rectangular film having a long side and a short side. In this application, the length L1 of the long side of the test specimen 80 is set to 150 mm, and the length L2 of the short side is set to 15 mm. As the loop stiffness measuring instrument 85, for example, the No. 581 Loop Stiffness Tester (registered trademark) LOOP STIFFNESS TESTER DA type manufactured by Toyo Seiki Co., Ltd. can be used. The length L1 of the long side of the test specimen 80 is adjustable insofar as the test specimen 80 can be gripped by a pair of chuck parts 86, which will be described later.

[0090] The loop stiffness measuring instrument 85 includes a pair of chucks 86 for gripping a pair of long-side ends of a test specimen 80, and a support member 87 for supporting the chucks 86. The chucks 86 include a first chuck 861 and a second chuck 862. In the state shown in Figures 13 and 14, the test specimen 80 is positioned on the pair of first chucks 861, and the second chuck 862 has not yet gripped the test specimen 80 between itself and the first chuck 861. 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 chucks 86. The second chuck 862 may be connected to the first chuck 861 via a hinge mechanism.

[0091] If the film to be measured, such as a biaxially oriented plastic film, a vapor-deposited film, or a laminated film, is available before it is processed into a packaging product, the test specimen 80 may be prepared by cutting the film to be measured. Alternatively, the test specimen 80 may be prepared by cutting a packaging product made from packaging material 30, such as a bag, and obtaining the target film. Figure 3 shows an example of a method for preparing a test specimen 80 from samples S1A to S2B obtained by cutting the packaging material 30 that constitutes the bag 10. When measuring loop stiffness in the flow direction, as indicated by the symbols S1A or S2A in Figure 3, the packaging material 30 of the bag 10 is cut so that the long side direction of the sample coincides with the flow direction, and then the target film, such as a biaxially oriented plastic film, is obtained from the sample. When measuring loop stiffness in the vertical direction, as indicated by the symbols S1B or S2B in Figure 3, the packaging material 30 of the bag 10 is cut so that the long side direction of the sample coincides with the vertical direction, and then the target film, such as a biaxially oriented plastic film, is obtained from the sample.

[0092] A method for measuring the loop stiffness of a test specimen 80 using a loop stiffness measuring instrument 85 will be described. First, as shown in Figures 13 and 14, the test specimen 80 is placed on the first chuck 861 of a pair of chuck portions 86 arranged with a gap L3 between them. In this application, the gap L3 is set so that the length of the loop portion 81 (hereinafter also referred to as the loop length), which will be described later, is 60 mm. The test specimen 80 includes an inner surface 80x located on the side of the first chuck 861 and an outer surface 80y located on the opposite side of the inner surface 80x. When the test specimen 80 is made of packaging material 30, the inner surface 80x and outer surface 80y of the test specimen 80 coincide with the inner surface 32 and outer surface 31 of the packaging material 30. When the loop portion 81, which will be described later, is formed on the test specimen 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 Figure 15, the second chuck 862 is placed on the test piece 80 so as to grip the long side end of the test piece 80 between it and the first chuck 861.

[0093] Next, as shown in Figure 16, 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 Figure 16 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 the parts of the test piece 80 that are gripped by the pair of chuck portions 86. The pair of intermediate portions 82 are the parts of the test piece 80 located between the loop portion 81 and the pair of intermediate portions 82. As shown in Figure 16, 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 with 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 the position P1 where the loop portion 81 side surface of one second chuck 862 intersects with the test piece 80, and the position P2 where the loop portion 81 side surface of the other second chuck 862 intersects with the test piece 80. The above-mentioned interval L3 is the length of the loop portion 81 plus 2 × t, where t is the thickness of the second chuck 862 of the chuck portion 86.

[0094] Subsequently, as shown in Figure 17, the posture of the chuck portion 86 is adjusted so that the protrusion 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 Figure 17, the protrusion direction Y of the loop portion 81 coincides with the thickness direction of the chuck portion. A load cell 88 is also prepared at a distance Z1 from the second chuck 862 in the protrusion 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 as shown in Figure 17. The distance Z2 is set so that the load cell 88 contacts the loop portion 81, and then the load cell 88 pushes the loop portion 81 toward the chuck portion 86, as shown in Figures 17 and 18. 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 86 when the load cell 88 is pushing the loop portion 81 toward the chuck portion 86 is 10 mm. The speed V used to move the load cell 88 was set to 3.3 mm / second.

[0095] Next, as shown in Figure 18, the load cell 88 is moved a distance Z2 toward the chuck portion 86, and while the load cell 88 is pressing against the loop portion 81 of the test piece 80, the load value applied from the loop portion 81 to the load cell 88 is recorded after it stabilizes. The load value obtained in this way is adopted as the loop stiffness of the film constituting the test piece 80. In this application, unless otherwise specified, the environment during the measurement of loop stiffness is a temperature of 23°C and a relative humidity of 50%.

[0096] The desirable mechanical properties of high-stiffness polyester films will be further explained. The puncture strength of the high-stiffness polyester film is preferably 10N or higher, and more preferably 11N or higher.

[0097] The breaking strength of the high-stiffness polyester film in at least one direction is preferably 250 MPa or more, and more preferably 280 MPa or more. For example, the breaking strength of the high-stiffness polyester film in the flow direction is preferably 250 MPa or more, and more preferably 280 MPa or more. Also, the breaking strength of the high-stiffness polyester film in the vertical direction is preferably 250 MPa or more, and more preferably 280 MPa or more. The elongation at break of the high-stiffness polyester film in at least one direction is preferably 130% or less, and more preferably 120% or less. For example, the elongation at break of the high-stiffness polyester film in the flow direction is preferably 130% or less, and more preferably 120% or less. Also, the elongation at break of the high-stiffness polyester film in the vertical direction is preferably 120% or less, and more preferably 110% or less. Preferably, in at least one direction, the value obtained by dividing the breaking strength of the high-stiffness polyester film by the elongation at break is 2.0 [MPa / %] or more. For example, the value obtained by dividing the breaking strength of the high-stiffness polyester film by the elongation at break in the vertical direction (TD) is preferably 2.0 [MPa / %] or more, and more preferably 2.2 [MPa / %] or more. The value obtained by dividing the breaking strength of the high-stiffness polyester film by the elongation at break in the flow direction (MD) is preferably 1.8 [MPa / %] or more, and more preferably 2.0 [MPa / %] or more.

[0098] The breaking strength and elongation at break of high-stiffness polyester film can be measured in accordance with JIS K7127. A tensile testing machine STA-1150 manufactured by Orientec Co., Ltd. can be used as the measuring instrument. A rectangular piece of high-stiffness polyester film, 15 mm wide and 150 mm long, can be used as the test specimen. The initial distance between the pair of chucks holding the test specimen is 100 mm, and the tensile speed is 300 mm / min. The length of the test specimen is adjustable as long as it can be gripped by the pair of chucks. Unless otherwise specified in this application, the environment for measuring breaking strength and elongation at break is 23°C and 50% relative humidity.

[0099] The thermal shrinkage rate of the high-stiffness polyester film in at least one direction is preferably 0.7% or less, and more preferably 0.5% or less. For example, the thermal shrinkage rate of the high-stiffness polyester film in the flow direction is preferably 0.7% or less, and more preferably 0.5% or less. The thermal shrinkage rate of the high-stiffness polyester film in the perpendicular direction is preferably 0.7% or less, and more preferably 0.5% or less. The heating temperature when measuring the thermal shrinkage rate 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 higher, and more preferably 4.5 MPa or higher. For example, the Young's modulus of the high-stiffness polyester film in the flow direction is preferably 4.0 GPa or higher, and more preferably 4.5 MPa or higher. The Young's modulus of the high-stiffness polyester film in the perpendicular direction is preferably 4.0 GPa or higher, and more preferably 4.5 GPa or higher.

[0100] The Young's modulus of high-stiffness polyester film can be measured in accordance with JIS K7127, similar to the breaking strength and elongation at breaking. A tensile testing machine STA-1150 manufactured by Orientec Co., Ltd. can be used as the measuring instrument. A rectangular piece of high-stiffness polyester film, 15 mm wide and 150 mm long, can be used as the test specimen. The initial distance between the pair of chucks holding the test specimen is 100 mm, and the tensile speed is 300 mm / min. The length of the test specimen is adjustable as long as it can be gripped by the pair of chucks. Unless otherwise specified in this application, the environment for measuring Young's modulus is a temperature of 23°C and a relative humidity of 50%.

[0101] In a packaging material 30 comprising a high-stiffness polyester film, the high-stiffness polyester film may be provided with a vapor-deposited layer. In this case, the high-stiffness polyester film provided with the vapor-deposited layer may have mechanical properties equivalent to those of a high-stiffness polyester film alone. For example, the high-stiffness polyester film provided with the vapor-deposited layer may have a loop stiffness of 0.0017 N or more in at least one direction.

[0102] In the manufacturing process of high-stiffness polyester film, for example, first, a plastic film obtained by melting and molding polyester is stretched to 3 to 4.5 times its original size in the flow direction and perpendicular direction at 90°C to 145°C, respectively, in a first stretching step. Subsequently, the plastic film is stretched to 1.1 to 3.0 times its original size in the flow direction and perpendicular direction at 100°C to 145°C, respectively, in a second stretching step. After that, heat setting is performed at a temperature of 190°C to 220°C. Subsequently, a relaxation treatment (a treatment to reduce the film width) of approximately 0.2% to 2.5% is performed in the flow direction and perpendicular direction at a temperature of 100°C to 190°C. By adjusting the stretching ratio, stretching temperature, heat setting temperature, and relaxation treatment rate in these steps, a high-stiffness polyester film with the above-mentioned mechanical properties can be obtained.

[0103] At least one of the first biaxially oriented plastic film 41 and the second biaxially oriented plastic film 42 may be an oriented plastic film containing polyamide as a main component. In the following description, a biaxially oriented plastic film containing polyamide as a main component will also be referred to as a biaxially oriented polyamide film. For example, one of the first biaxially oriented plastic film 41 and the second biaxially oriented plastic film 42 may be a biaxially oriented polyamide film and the other may be a biaxially oriented polyester film.

[0104] The biaxially oriented polyamide film contains, for example, 51% by mass or more of polyamide. Examples of polyamides include aliphatic polyamides and aromatic polyamides. Examples of aliphatic polyamides include nylon such as nylon-6, nylon-6,6, and copolymers of nylon-6 and nylon-6,6, while examples of aromatic polyamides include polymetaxylene adipamide (MXD6). By including a biaxially oriented polyamide film in the packaging material 30, the puncture strength of the packaging material 30 can be increased.

[0105] A biaxially oriented polyamide film may consist of a single layer or multiple layers. When a biaxially oriented polyamide film contains multiple layers, it is, for example, a co-extruded film produced by co-extrusion. The co-extruded film includes, for example, a first layer made of polyester such as PET, a second layer made of polyamide such as nylon, and a third layer made of polyester such as PET, which are laminated in order. If the mass of the second layer made of polyamide such as nylon is 51% or more of the total mass of the co-extruded film, then the main component of the co-extruded film can be said to be polyamide.

[0106] The thickness of the biaxially oriented polyamide film is preferably 12 μm or more, and more preferably 15 μm or more. Furthermore, the thickness of the biaxially oriented polyamide film is preferably 25 μm or less, and more preferably 20 μm or less.

[0107] An example of a combination of the first biaxially oriented plastic film 41 and the second biaxially oriented plastic film 42 in this embodiment is as follows. [Table 1]

[0108] Examples of biaxially oriented polyester films include the biaxially oriented PET film, biaxially oriented PBT film, and high-stiffness polyester film mentioned above. Detailed specific examples of the combinations of Examples 1, 2, and 3 shown in Table 1 are shown in Tables 2, 3, and 4, respectively. [Table 2] [Table 3] [Table 4]

[0109] If the biaxially oriented plastic films 41 and 42 contain PET, the PET may also contain biomass-derived PET. In this case, the biaxially oriented plastic films 41 and 42 may consist solely of biomass-derived PET. Alternatively, the biaxially oriented plastic films 41 and 42 may consist of biomass-derived PET and fossil fuel-derived PET. By including biomass-derived PET in the biaxially oriented plastic films 41 and 42, the amount of fossil fuel-derived PET can be reduced compared to conventional methods, thereby reducing carbon dioxide emissions and the environmental burden. Biomass-derived PET consists of biomass-derived ethylene glycol as a diol unit and fossil fuel-derived terephthalic acid as a dicarboxylic acid unit. Fossil fuel-derived PET consists of fossil fuel-derived ethylene glycol as a diol unit and fossil fuel-derived terephthalic acid as a dicarboxylic acid unit.

[0110] Atmospheric carbon dioxide contains a certain proportion (105.5 pMC) of C14, and it is known that the C14 content in plants that grow by taking in atmospheric carbon dioxide, such as corn, is also around 105.5 pMC. It is also known that fossil fuels contain almost no C14. Therefore, by measuring the proportion of C14 contained in the total carbon atoms in PET, the proportion of carbon derived from biomass can be calculated. In this invention, "biomass degree" refers to the weight ratio of biomass-derived components. Taking PET as an example, PET is a polymer of ethylene glycol containing 2 carbon atoms and terephthalic acid containing 8 carbon atoms in a molar ratio of 1:1. If only biomass-derived ethylene glycol is used in PET, the weight ratio of biomass-derived components in PET is 31.25%, so the theoretical value of the biomass degree 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 biaxially oriented plastic films 41 and 42 is preferably 5.0% or more, and more preferably 10.0% or more. In addition, the biomass content of the biaxially oriented plastic films 41 and 42 is preferably 30.0% or less.

[0111] Biomass-derived ethylene glycol is produced using ethanol (biomass ethanol) made from biomass as a raw material. For example, biomass-derived ethylene glycol can be obtained by conventionally known methods, such as producing ethylene glycol via ethylene oxide from biomass ethanol. Examples of raw materials for biomass ethanol include corn, sugarcane, beets, and manioc. Commercially available biomass ethylene glycol may also be used; for example, the biomass ethylene glycol commercially available from India Glycol is suitably used. Note that India Glycol's biomass ethylene glycol is made from sugarcane molasses.

[0112] Next, we will describe the adhesive layer 43 located between the first biaxially oriented plastic film 41 and the second biaxially oriented plastic film 42 in the packaging material 30 shown in Figures 5 to 9. The adhesive layer 43 is either an adhesive layer or an adhesive resin layer. The adhesive layer and the adhesive resin layer will be described below, respectively.

[0113] The adhesive layer can be formed by conventionally known methods, such as the dry lamination method. When bonding two layers by the dry lamination method, the adhesive layer is formed by applying the adhesive to the surface of the layer to be laminated and drying it. As the adhesive to be applied, for example, one-component or two-component curing or non-curing type adhesives such as vinyl-based, (meth)acrylic-based, polyamide-based, polyester-based, polyether-based, polyurethane-based, epoxy-based, rubber-based, and others can be used, and are available in solvent-type, water-type, or emulsion-type adhesives. As a two-component curing type adhesive, a cured product of a polyol and an isocyanate compound can be used. As a coating method for the above laminating adhesive, for example, it can be applied by the direct gravure roll coating method, gravure roll coating method, kiss coating method, reverse roll coating method, fontein method, transfer roll coating method, and other methods. After drying, the adhesive layer has a thickness of, for example, 1 μm to 10 μm, preferably 2 μm to 5 μm.

[0114] The adhesive layer may contain biomass-derived components. For example, if the adhesive layer contains a cured product of a polyol and an isocyanate compound, at least one of the polyol or the isocyanate compound may contain biomass-derived components. This can further improve the biomass content of the packaging material 30.

[0115] The adhesive resin layer contains a thermoplastic resin. The adhesive resin layer can be formed by conventionally known methods, such as melt extrusion lamination or sand lamination. Suitable thermoplastic resins for the adhesive resin layer include polyethylene resins, polypropylene resins, or cyclic polyolefin resins, or copolymer resins, modified resins, or mixtures of these resins. Examples of polyolefin resins include low-density polyethylene (LDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), polypropylene (PP), ethylene-α-olefin copolymers polymerized using metallocene catalysts, random or block copolymers of ethylene-polypropylene, ethylene-vinyl acetate copolymer (EVA), ethylene-acrylic acid copolymer (EAA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methacrylic acid copolymer (EMAA), ethylene-methyl methacrylate copolymer (EMMA), ethylene-maleic acid copolymer, and ionomer resins. Furthermore, to improve interlayer adhesion, acid-modified polyolefin resins can be used, which are obtained by modifying the above-mentioned polyolefin resins with unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, and itaconic acid. Additionally, resins obtained by graft polymerization or copolymerization of polyolefin resins with unsaturated carboxylic acids, unsaturated carboxylic acid anhydrides, or ester monomers can be used. These materials can be used individually or in combination of two or more. Examples of cyclic polyolefin resins include ethylene-propylene copolymers, polymethylpentene, polybutene, polynorvonene, and other cyclic polyolefins. These resins can be used individually or in combination of several. The adhesive resin layer has a thickness of, for example, 5 μm to 50 μm, preferably 10 μm to 30 μm.

[0116] Furthermore, the polyethylene resin mentioned above may be one that uses biomass-derived ethylene as the monomer unit. This can further improve the biomass content of the packaging material 30.

[0117] Next, the biaxially oriented plastic film 44 of the packaging material 30 shown in Figures 10 to 12 will be described in detail. As the biaxially oriented plastic film 44, either the biaxially oriented plastic film exemplified as the first biaxially oriented plastic film 41 or the second biaxially oriented plastic film 42 described above can be used. For example, the biaxially oriented plastic film 44 may be the biaxially oriented polyester film described above, which contains polyester as the main component. Examples of biaxially oriented polyester films include the biaxially oriented PET film, biaxially oriented PBT film, and high-stiffness polyester film described above. In addition, the biaxially oriented plastic film 44 may be a biaxially oriented polyamide film, which contains polyamide as the main component.

[0118] If the biaxially oriented plastic film 44 contains PET, the PET may also contain biomass-derived PET, as in the case of the first biaxially oriented plastic film 41 or the second biaxially oriented plastic film 42.

[0119] Next, the pattern layer 45 of the packaging material 30 shown in Figures 5 to 12 will be described. The pattern layer 45 is a layer provided on the packaging material 30 to indicate information about the contents or container, or to add an aesthetic appeal to a container such as a bag 10. The pattern layer 45 can represent letters, numbers, symbols, figures, pictures, etc. Gravure printing inks or flexographic printing inks can be used as materials to make up the pattern layer 45. A specific example of a gravure printing ink is Finart manufactured by DIC Graphics Corporation.

[0120] (Sealant layer) Next, the sealant layer 50 will be described. The sealant layer 50 has heat-sealing properties and is a layer that constitutes the inner surface 32 of the packaging material 30. The sealant layer 50 contains a thermoplastic resin. Examples of thermoplastic resins 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.

[0121] Low-density polyethylene has a density of 0.910 g / cm³. 3 The above and 0.925 g / cm³ 3 The following polyethylenes are used. Medium-density polyethylene has a density of 0.926 g / cm³. 3 The above and 0.940 g / cm³ 3 The following polyethylenes are used. High-density polyethylene has a density of 0.941 g / cm³. 3 The above and 0.965 g / cm³ 3 The following polyethylenes are used. Low-density polyethylene is obtained, for example, by polymerizing ethylene at a high pressure of 1000 atmospheres or more and less than 2000 atmospheres. Medium-density polyethylene and high-density polyethylene are obtained, for example, by polymerizing ethylene at a medium or low pressure of 1 atmosphere or more and less than 1000 atmospheres.

[0122] Medium-density polyethylene and high-density polyethylene may partially contain copolymers of ethylene and α-olefins. Furthermore, even when polymerizing ethylene at medium or low pressure, medium-density or low-density polyethylene can be produced if it contains copolymers of ethylene and α-olefins. Such polyethylene is referred to as the linear low-density polyethylene described above. Linear low-density polyethylene is obtained by copolymerizing a linear polymer obtained by polymerizing ethylene at medium or low pressure with α-olefins to introduce short-chain branching. Examples of α-olefins include 1-butene (C4), 1-hexene (C6), 4-methylpentene (C6), and 1-octene (C8), with 1-butene (C4) being particularly preferred. The density of linear low-density polyethylene is, for example, 0.915 g / cm³. 3 The above and 0.945 g / cm³ 3 The following applies:

[0123] The thickness of the sealant layer 50 is preferably 10 μm or more. Alternatively, the thickness of the sealant layer 50 may be, for example, 200 μm or less, 150 μm or less, or 100 μm or less.

[0124] The sealant layer 50 may be a layer obtained by laminating a sealant film 51, which has been pre-formed using a method such as inflation, to the substrate 40 via an adhesive layer 61 or the like, as shown in Figures 5, 8, 9, and 10. Alternatively, the sealant layer 50 may be a layer obtained by coating the substrate 40 or the like with the materials constituting the sealant layer 50 using an extrusion coating method, as shown in Figures 6, 7, 11, and 12.

[0125] Preferably, the sealant layer 50 has a low elongation at break or low breaking strength at the microwave heating temperature. This makes it easier for the sealant layer 50 to break in the portion located in the first region 33 after the laminate strength adjustment layer 35 has peeled off from the sealant layer 50. This makes it easier for steam to escape to the outside of the bag 10 through the break in the sealant layer 50.

[0126] The following describes preferred properties of the sealant film 51 when the sealant layer 50 is made of the sealant film 51.

[0127] Preferably, the sealant film 51 has a break elongation of 60% to 100% at 80°C in one direction, for example, in the flow direction. Having a break elongation of 100% or less at 80°C allows the sealant layer 50 to be properly broken in at least a portion of the first region 33 of the packaging material 30 at the microwave heating temperature. Furthermore, having a break elongation of 60% or more at 80°C ensures seal strength in the sealed area. Additionally, it is possible to suppress breakage of the sealant layer 50 in the second region 34.

[0128] Furthermore, the sealant film 51 preferably has a break elongation of 40% to 70% at 90°C in one direction, for example, in the flow direction.

[0129] Furthermore, the sealant film 51 has a breaking strength of 5N to 10N at 80°C in one direction, for example, in the flow direction. The breaking strength of the sealant film 51 at 80°C being 10N or less allows the sealant layer 50 to be properly broken in at least a portion of the first region 33 of the packaging material 30 at the microwave heating temperature. Additionally, the breaking strength of the sealant film 51 at 80°C being 5N or more suppresses the occurrence of rupture in the sealant layer 50 in the second region 34.

[0130] The elongation at break and breaking strength of the sealant film 51 can be measured in accordance with JIS K7127. A No.260 Strograph VG1F manufactured by Toyo Seiki Co., Ltd. can be used as the measuring instrument. A rectangular film of sealant film 51 with a width of 15 mm and a length of 150 mm can be used as the test specimen. The initial distance between the pair of chucks holding the test specimen is 50 mm, and the tensile speed is 200 mm / min. The length of the test specimen is adjustable as long as it can be gripped by the pair of chucks.

[0131] In this application, unless otherwise specified, the breaking strength and elongation at high temperatures of the sealant film 51 are measured after holding the test specimen in an environment of 80°C and 5% relative humidity for 1 minute. Furthermore, the breaking strength and elongation at room temperature of the sealant film 51 are measured after holding the test specimen in an environment of 25°C and 50% relative humidity for 1 minute.

[0132] According to novel findings from the inventors' research and development, a phenomenon was observed in multiple types of sealant films containing the same material and having equivalent density, MFR, melting point, etc., where the sealant film material was manufactured in different factories: the elongation at the breaking point of the sealant film differed at microwave heating temperatures such as 80°C. The inventors' considerations suggest that this is because the ratio of the heat of fusion of the sealant film, one of the material's properties, differs at microwave heating temperatures due to differences in manufacturing conditions. The ratio of the heat of fusion of the sealant film can be expressed as the ratio of the heat of fusion at microwave heating temperatures (e.g., 80°C, 90°C, 100°C) to the total heat of fusion of the material (50°C to 120°C), using differential scanning calorimetry (DSC). A high ratio of the heat of fusion of the sealant film at microwave heating temperatures means that a relatively large amount of material is melted in the sealant film at microwave heating temperatures. The inventors of this case have confirmed that sealant films with particularly low elongation at the break point in the flow direction at microwave heating temperatures have a high proportion of the heat of fusion of the sealant film.

[0133] The sealant layer 50 may or may not contain biomass-derived components. When the sealant layer 50 is formed using a material containing biomass-derived components, the sealant layer 50 can be formed using the biomass polyolefins described below. When the sealant layer 50 is formed using a material that does not contain biomass-derived components, the sealant layer 50 can be formed using conventionally known thermoplastic resins derived from fossil fuels.

[0134] Biomass polyolefins are polymers of monomers containing olefins such as ethylene derived from biomass. Because biomass-derived olefins are used as raw material monomers, the resulting polyolefins are biomass-derived. However, the raw material monomers for polyolefins do not necessarily have to contain 100% by mass of biomass-derived olefins.

[0135] For example, biomass-derived ethylene can be produced using biomass-derived ethanol as a raw material. In particular, it is preferable to use biomass-derived fermented ethanol obtained from plant materials. The plant materials are not particularly limited, and conventionally known plants can be used. Examples include corn, sugarcane, beet, and manioc.

[0136] Biomass-derived fermented ethanol refers to ethanol produced by contacting a culture medium containing a carbon source obtained from plant raw materials with microorganisms that produce ethanol or products derived from their crushed material, and then purifying the ethanol. Conventional known methods such as distillation, membrane separation, and extraction can be applied to purify the ethanol from the culture medium. For example, methods such as adding benzene, cyclohexane, etc., and azeotropic distillation, or removing water by membrane separation, etc., can be used.

[0137] The monomers used as raw materials for biomass polyolefins may further include ethylene monomers derived from fossil fuels and / or α-olefin monomers derived from fossil fuels, or may further include α-olefin monomers derived from biomass.

[0138] The above-mentioned α-olefin is not particularly limited in terms of the number of carbon atoms, but typically those with 3 to 20 carbon atoms can be used, and butylene, hexene, or octene are preferred. This is because butylene, hexene, or octene can be produced by polymerization of ethylene, which is a biomass-derived raw material. Furthermore, by including such an α-olefin, the polymerized polyolefin has alkyl groups as branched structures, making it more flexible than simple linear polyolefins.

[0139] As the biomass polyolefin, polyethylene or a copolymer of ethylene and an α-olefin may be used alone, or two or more of them may be mixed and used. In particular, the biomass polyolefin is preferably polyethylene. This is because by using ethylene which is a raw material derived from biomass, it becomes possible to manufacture it from 100% components derived from biomass theoretically.

[0140] The biomass polyolefin may contain two or more biomass polyolefins having different biomass degrees, and as the whole polyolefin resin layer, the biomass degree may be within the range described later.

[0141] The biomass polyolefin preferably has a density of 0.91 g / cm 3 or more and 0.93 g / cm 3 or less, more preferably 0.912 g / cm 3 or more and 0.928 g / cm 3 or less, even more preferably 0.915 g / cm 3 or more and 0.925 g / cm 3 or less. The density of the biomass polyolefin is a value measured according to the method specified in Method A of JIS K7112-1980 after annealing described in JIS K6760-1995. If the density of the biomass polyolefin is 0.9 g / cm 3 or more, the rigidity of the polyolefin resin layer containing the biomass polyolefin can be increased, and it can be suitably used as the inner layer of the packaging product. Also, if the density of the biomass polyolefin is 0.93 g / cm 3 or less, the transparency and mechanical strength of the polyolefin resin layer containing the biomass polyolefin can be increased, and it can be suitably used as the inner layer of the packaging product.

[0142] The biomass polyolefin has a melt flow rate (MFR) of 0.1 g / 10 min to 10 g / 10 min, preferably 0.2 g / 10 min to 9 g / 10 min, and more preferably 1 g / 10 min to 8.5 g / 10 min. The melt flow rate is a value measured by Method A under the conditions of a temperature of 190°C and a load of 21.18 N, as specified in JIS K7210-1995. If the MFR of the biomass polyolefin is 0.1 g / 10 min or higher, the extrusion load during molding can be reduced. Furthermore, if the MFR of the biomass polyolefin is 10 g / 10 min or lower, the mechanical strength of the polyolefin resin layer containing the biomass polyolefin can be increased.

[0143] Suitable biomass polyolefins include low-density polyethylene derived from biomass, manufactured by Braskem (product name: SBC818, density: 0.918 g / cm³). 3 MFR: 8.1g / 10 min, Biomass content 95%, Low-density polyethylene derived from biomass manufactured by Braskem (product name: SPB681, density: 0.922g / cm³) 3 MFR: 3.8g / 10 min, Biomass content 95%, Biomass-derived linear low-density polyethylene (product name: SLL118, density: 0.916g / cm³) manufactured by Braskem. 3 Examples include MFR: 1.0g / 10min, biomass content 87%).

[0144] Next, the adhesive layer 61 and anchor coat layer 62, which are layers used to laminate the sealant layer 50, will be described.

[0145] The adhesive layer 61 can be formed by a conventionally known method, such as a dry lamination method, similar to the adhesive layer of the adhesive layer 43 described above. As the adhesive for the adhesive layer 61, the adhesive exemplified in the adhesive layer of the adhesive layer 43 described above can be used.

[0146] The anchor coat layer 62 is a layer that enhances the adhesion between the substrate 40 and the sealant layer 50. The resin used to make up the anchor coat layer 62 can be a vinyl-modified resin, epoxy resin, urethane resin, polyester resin, or the like.

[0147] (Laminate strength adjustment layer) Next, the laminate strength adjustment layer 35 will be described. The laminate strength adjustment layer 35 is a layer that contains resin and softens when heated. The laminate strength adjustment layer 35 can be formed using a resin material having a melting point of 60 to 110°C.

[0148] The resin material constituting the laminate strength adjustment layer 35 will be described below. The laminate strength adjustment layer 35 can be formed using a resin containing, for example, polyamide, cellulose, and an ethylene-vinyl acetate copolymer resin. Alternatively, the laminate strength adjustment layer 35 can also be formed using a resin containing, for example, polyamide, cellulose, and polyolefin wax. Cellulose is, for example, nitrated cotton. Polyolefin wax is, for example, polyethylene wax. As a resin containing polyamide, nitrated cotton, and polyethylene wax, MWOP varnish (softening point: 105°C) manufactured by DIC Graphics Co., Ltd. can be used.

[0149] The thickness of the laminate strength adjustment layer 35 is preferably 1 μm or more and 5 μm or less. If the thickness of the laminate strength adjustment layer 35 is 1 μm or more, it is possible to cause a rupture between the laminate strength adjustment layer 35 and the sealant layer 50 when heated in a microwave oven. Also, if the thickness of the laminate strength adjustment layer 35 is too large, depending on the pattern of the laminate strength adjustment layer, when the film-like packaging material 30 is wound into a roll, a part of it may bulge, and the packaging material in that part may stretch. However, if the thickness of the laminate strength adjustment layer 35 is 5 μm or less, such stretching of the packaging material 30 can be suppressed.

[0150] (Other layers) The packaging material 30 may include a vapor-deposited layer located on the surface of the first biaxially oriented plastic film 41 or the second biaxially oriented plastic film 42. The packaging material 30 may further include a transparent gas barrier coating film located on the surface of the vapor-deposited layer.

[0151] The vapor-deposited layer is a layer provided on the packaging material 30 to enhance the gas barrier properties of the packaging material 30. The vapor-deposited layer is a transparent vapor-deposited layer formed of a transparent inorganic material such as aluminum oxide (aluminum oxide) or silicon oxide. Two or more vapor-deposited layers 37 may be provided. If there are two or more vapor-deposited layers 37, each may have the same composition or different compositions.

[0152] Examples of methods for forming the vapor-deposited layer include physical vapor deposition (PVD) methods such as vacuum deposition, sputtering, and ion plating, or chemical vapor deposition (CVD) methods such as plasma chemical vapor deposition, thermochemical vapor deposition, and photochemical vapor deposition. Specifically, the vapor-deposited layer can be formed on a deposition roller using a roller-type vapor deposition apparatus. The thickness of the vapor-deposited layer is, for example, 20 Å or more and 200 Å, preferably 30 Å or more and 150 Å, and more preferably 50 Å or more and 120 Å or less. The thickness of the vapor-deposited layer can be measured, for example, by the fundamental parameter method using an X-ray fluorescence analyzer (product name: RIX2000, manufactured by Rigaku Corporation).

[0153] A gas barrier coating is a layer that functions to suppress the permeation of oxygen gas and water vapor. The gas barrier coating is generally represented by formula R 1 n M(OR 2 ) m (However, in the formula, R 1 , R 2The transparent gas barrier composition is obtained by polycondensing a polyvinyl alcohol resin and / or ethylene-vinyl alcohol copolymer as described above, in the presence of a sol-gel catalyst, acid, water, and an organic solvent. (where 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.)

[0154] (Layer structure of the packaging material on the upper surface film) Next, the packaging material constituting the upper surface film 141 will be described. As the packaging material constituting the upper surface film 141, a packaging material 30 partially comprising a laminate strength adjustment layer 35 may be used, similar to the lower surface film 142. In this case, the laminate strength adjustment layer 35 of the upper surface film 141 may be arranged to overlap with the laminate strength adjustment layer 35 of the lower surface film 142. Alternatively, the packaging material constituting the upper surface film 141 may be the same as the packaging material 30 described above, except that it does not have a laminate strength adjustment layer 35. In other words, the packaging material 30, in which the entire area is composed of the second region 34 described above, may be used as the upper surface film 141. Although not shown in the diagram, instead of providing the lamination strength adjustment layer 35 on the lower surface film 142, the lamination strength adjustment layer 35 may be provided on the portion of the upper surface film 141 that constitutes the girdle portion 20.

[0155] (Layer structure of the packaging material on the back film) Next, the layer structure of the back film 15 will be described. The layer configuration of the lower film 16 is arbitrary, as long as it has an inner surface that can be joined to the inner surface of the upper surface film 141, the inner surface of the lower surface film 142, and the inner surface of the lower film 16. For example, the back film 15 may be the same as the packaging material 30 described above, except that it does not have a laminate strength adjustment layer 35. In other words, the packaging material 30 whose entire area is composed of the second region 34 described above may be used as the back film 15. Alternatively, a film with a different configuration from the second region 34 may be used as the back film 15.

[0156] (Layer structure of the packaging material in the lower film) Next, the layer structure of the lower film 16 will be described. The layer configuration of the lower film 16 is arbitrary, as long as it has an inner surface that can be joined to the inner surface of the lower surface film 142 and the inner surface of the back film 15. For example, the lower film 16 may be the same as the packaging material 30 described above, except that it does not have a laminate strength adjustment layer 35. In other words, the packaging material 30 whose entire area is composed of the second region 34 described above may be used as the lower film 16. Alternatively, a film with a different configuration from the second region 34 may be used as the lower film 16.

[0157] Manufacturing method for packaging materials Next, an example of a method for manufacturing the packaging material 30 will be described.

[0158] First, prepare the base material 40 as described above. In the examples shown in Figures 5 to 9, the first biaxially oriented plastic film 41 and the second biaxially oriented plastic film 42 are laminated together via an adhesive layer 43 by using a lamination method such as dry lamination or sand lamination. This allows the base material 40 to be obtained. If the pattern layer 45 is located between the first biaxially oriented plastic film 41 and the second biaxially oriented plastic film 42, the pattern layer 45 is provided on either the first biaxially oriented plastic film 41 or the second biaxially oriented plastic film 42 before the lamination process. In the examples shown in Figures 10 to 12, a biaxially oriented plastic film 44 that functions as a base material 40 is prepared.

[0159] Next, if necessary, a pattern layer 45 is formed on the inner surface of the base material 40, and then a laminate strength adjustment layer 35 is partially formed on the inner surface of the base material 40 or the inner surface of the pattern layer 45. For example, while conveying the base material 40 in the flow direction, the material constituting the laminate strength adjustment layer 35 is applied to the area of ​​the base material 40 that overlaps with the area where the first end seal portion 13 and the girth seal portion 15 intersect, and the area that overlaps with the area where the second end seal portion 14 and the girth seal portion 15 intersect. The flow direction of the base material 40 corresponds to the first direction D1 shown in Figure 4.

[0160] Next, a sealant layer 50 is laminated onto a substrate 40 on which a laminate strength adjustment layer 35 is partially provided. For example, the substrate 40 and the sealant film 51 are laminated via an adhesive layer 61 by a dry lamination method. Alternatively, the material constituting the sealant layer 50 is coated onto the substrate 40 by an extrusion coating method. Prior to coating, the above-mentioned anchor coat layer 62 may be formed on the substrate 40. In this way, a packaging material 30 can be obtained that comprises at least the substrate 40, the laminate strength adjustment layer 35, and the sealant layer 50 in order from the outer surface 31 to the inner surface 32.

[0161] Characteristics of packaging materials Next, the properties of the packaging material 30 will be described. Specifically, the elongation at break, breaking strength, and laminate strength of the packaging material 30 will be described. First, the environment and measurement method for measuring the elongation at break, breaking strength, and laminate strength will be described.

[0162] In the following description, the elongation at break in the first region 33 of the packaging material 30 will also be referred to as the first elongation at break, and the elongation at break in the second region 34 of the packaging material 30 will also be referred to as the second elongation at break. Furthermore, of the first and second elongations at break, the elongations at break obtained by holding a test piece of the packaging material 30 in an environment of 80°C and 5% relative humidity for 1 minute, and then measuring it in an environment of 80°C and 5% relative humidity, will also be referred to as the high-temperature first elongation at break and the high-temperature second elongation at break, respectively. Furthermore, of the first and second elongations at break, the elongations at break obtained by holding a test piece of the packaging material 30 in an environment of 25°C and 50% relative humidity for 1 minute, and then measuring it in an environment of 25°C and 50% relative humidity, will also be referred to as the room-temperature first elongation at break and the room-temperature second elongation at break, respectively.

[0163] Furthermore, in the following description, the breaking strength in the first region 33 of the packaging material 30 will also be referred to as the first breaking strength, and the breaking strength in the second region 34 of the packaging material 30 will also be referred to as the second breaking strength. In addition, of the first and second breaking strengths, the breaking strengths obtained by holding a test piece of the packaging material 30 in an environment of 80°C and 5% relative humidity for 1 minute, and then measuring it in an environment of 80°C and 5% relative humidity, will also be referred to as the high-temperature first breaking strength and high-temperature second breaking strength, respectively. In addition, of the first and second breaking strengths, the breaking strengths obtained by holding a test piece of the packaging material 30 in an environment of 25°C and 50% relative humidity for 1 minute, and then measuring it in an environment of 25°C and 50% relative humidity, will also be referred to as the room-temperature first breaking strength and room-temperature second breaking strength, respectively.

[0164] The elongation at break and breaking strength of the packaging material 30 can be measured in accordance with JIS K7127. A No.260 Strograph VG1F manufactured by Toyo Seiki Co., Ltd. can be used as the measuring instrument. As the test specimen, a rectangular film of the packaging material 30 with a width of 15 mm and a length of 150 mm can be used. The initial distance between the pair of chucks holding the test specimen is 50 mm, and the tensile speed is 200 mm / min. The length of the test specimen is adjustable as long as it can be gripped by the pair of chucks.

[0165] If the packaging material 30 is available in its unprocessed state, before being made into a container such as a bag 10, a test specimen of the packaging material 30 is prepared by cutting the packaging material 30 before processing. Alternatively, a test specimen of the packaging material 30 may be prepared by cutting a container made from the packaging material 30, such as a bag 10. For example, when measuring the elongation at break and breaking strength of the packaging material 30 in the flow direction, the packaging material 30 of the bag 10 may be cut so that the direction of the long side of the test piece coincides with the flow direction of the packaging material 30, as indicated by the symbols S1A or S2A in Figure 3. Test piece S1A is for measuring the elongation at break and breaking strength of the first region 33 of the packaging material 30 in the flow direction, and includes at least a portion of the laminate strength adjustment layer 35. Test piece S2A is for measuring the elongation at break and breaking strength of the second region 34 of the packaging material 30 in the flow direction, and does not include the laminate strength adjustment layer 35. Furthermore, for example, when measuring the elongation at break and breaking strength of the packaging material 30 in the vertical direction, the packaging material 30 of the bag 10 may be cut so that the direction of the long side of the test piece coincides with the vertical direction of the packaging material 30, as indicated by the symbols S1B or S2B in Figure 3. Test piece S1B is for measuring the elongation at break and breaking strength of the first region 33 of the packaging material 30 in the vertical direction, and includes at least a portion of the laminate strength adjustment layer 35. Test piece S2B is for measuring the elongation at break and breaking strength of the second region 34 of the packaging material 30 in the vertical direction, and does not include the laminate strength adjustment layer 35.

[0166] Furthermore, in the following description, the lamination strength in the first region 33 of the packaging material 30 will also be referred to as the first lamination strength, and the lamination strength in the second region 34 of the packaging material 30 will also be referred to as the second lamination strength. In addition, among the first and second lamination strengths, the lamination strengths obtained by holding a test piece of the packaging material 30 in an environment of 80°C and 5% relative humidity for 1 minute and then measuring it in an environment of 80°C and 5% relative humidity will be referred to as the high-temperature first lamination strength and high-temperature second lamination strength, respectively. In addition, among the first and second lamination strengths, the lamination strengths obtained by holding a test piece of the packaging material 30 in an environment of 25°C and 50% relative humidity for 1 minute and then measuring it in an environment of 25°C and 50% relative humidity will be referred to as the room-temperature first lamination strength and room-temperature second lamination strength, respectively.

[0167] The laminate strength of the packaging material 30 can be measured in accordance with JIS K7127. A No.260 Strograph VG1F manufactured by Toyo Seiki Co., Ltd. can be used as the measuring instrument. As with the cases of elongation at break and breaking strength, a rectangular film cut from the packaging material 30 with a width of 15 mm and a length of 150 mm can be used as the test specimen. The length of the test specimen can be adjusted as long as the interval S described later can be secured. As with the cases of elongation at break and breaking strength, the test specimen may also be made by cutting a container made from the packaging material 30, such as a bag 10. In the case of the test specimen of the first region 33 of the packaging material 30, it is preferable that the laminate strength adjustment layer 35 extends over the entire width of the test specimen in at least a portion of the specimen.

[0168] The method for measuring the laminate strength of the packaging material 30 will be described below with reference to Figures 19 to 24. First, the test specimen for measuring the laminate strength of the packaging material 30 will be described.

[0169] Figure 19 is a cross-sectional view showing an example of a test specimen 91 for measuring the laminate strength of a first region 33 of a packaging material 30. The test specimen 91 shown in Figure 19 includes a laminate strength adjustment layer 35 that extends over the entire longitudinal region of the test specimen 91. First, as shown in Figure 19, the substrate 40 and sealant layer 50 of the test specimen 91 are partially peeled off from the leading edge of the test specimen 91 in the long direction, for example, over a distance of 15 mm. At this time, the laminate strength adjustment layer 35 may be located on the substrate 40 side, as shown in Figure 19.

[0170] Figure 20 is a cross-sectional view showing another example of a test specimen 91 for measuring the laminate strength of a first region 33 of the packaging material 30. As shown in Figure 20, the test specimen 91 may include a laminate strength adjusting layer 35 that extends over a portion of the longitudinal direction of the test specimen 91.

[0171] Figure 21 is a cross-sectional view showing a test specimen 92 for measuring the laminate strength of a second region 34 of the packaging material 30. The test specimen 92 does not include the laminate strength adjustment layer 35.

[0172] Next, we will describe the process of measuring the laminate strength of the packaging material 30 using test specimens 91 and 92. Here, we will describe an example using test specimen 91 shown in Figure 20.

[0173] As shown in Figure 22, one of the substrate 40 and the sealant layer 50 is placed on the support base 93 side of the measuring instrument, and the already peeled portion of the other substrate 40 and sealant layer 50 is gripped by the gripper 94 of the measuring instrument. The part of the substrate 40 and sealant layer 50 that is on the support base 93 side is fixed to the support base 93 with a fixing device 95 as shown in Figure 22. For example, the substrate 40 side is gripped by the gripper 94, and the sealant layer 50 side is fixed to the support base 93. Furthermore, the gripper 94 is pulled at a speed of 50 mm / min in a direction in which the surface of the substrate 40 gripped by the gripper 94 forms a 180° angle with the surface of the sealant layer 50 fixed to the support base 93, and the tensile force T applied by the gripper 94 to the test piece is measured. The distance S between the gripping device 94 and the fixing device 95 in the direction of movement of the gripping device 94 at the start of pulling is 30 mm, and the distance S at the end of pulling is 60 mm.

[0174] Figure 23 shows the change in tensile force with respect to the distance S between the grippers 93 and 94 when using the test specimen 91 shown in Figure 20. As shown in Figure 23, the tensile force value shows a second tensile force in the second peeling region after passing through a transition region, a first tensile force in the first peeling region, and then a second tensile force in the second peeling region. The second peeling region is the region observed when peeling the substrate 40 and the sealant layer 50 in the region of the test specimen shown in Figure 20 where the laminate strength adjustment layer 35 is absent. The first peeling region is the region observed when peeling the substrate 40 and the sealant layer 50 in the region of the test specimen shown in Figure 20 where the laminate strength adjustment layer 35 is present. In this application, the average value of the tensile force in the first peeling region was calculated for each of the five test specimens 91, and this average value was taken as the laminate strength (first laminate strength) in the first region 33 of the packaging material 30.

[0175] Figure 24 shows the change in tensile force with respect to the distance S between the grippers 93 and 94 when using the test specimen 92 shown in Figure 21. As shown in Figure 24, the tensile force value shows a second tensile force in the second peel region after passing through the transition region. In this application, the average value of the tensile force in the second peel region was calculated for each of the five test specimens 92, and this average value was taken as the laminate strength (second laminate strength) in the second region 34 of the packaging material 30.

[0176] Next, the preferred ranges for the elongation at break and the breaking strength of the packaging material 30 will be described.

[0177] [Elongation and strength at break of the first type of packaging material] First, we will describe the case where the base material 40 of the packaging material 30 includes a first biaxially oriented plastic film 41 and a second biaxially oriented plastic film 42, and both the first biaxially oriented plastic film 41 and the second biaxially oriented plastic film 42 contain polyester as the main component. In the following description, such a packaging material 30 will also be referred to as the first type of packaging material 30.

[0178] In the first type of packaging material 30, preferably, the high-temperature second elongation at break is 180% or less in at least one direction. The elongation at break of the packaging material 30 is a property that is mainly determined by the mechanical properties of the base material 40 and the sealant layer 50, especially in the flow direction, and the laminate strength adjustment layer 35 is not considered to contribute much to the elongation at break. Therefore, if the high-temperature second elongation at break of the packaging material 30 is 180% or less, the high-temperature first elongation at break of the packaging material 30 is also expected to be 180% or less.

[0179] By having a high-temperature first elongation at break of 180% or less, after delamination of the laminate strength adjustment layer 35 occurs in the first region 33 of the packaging material 30 at the microwave heating temperature, a portion of the packaging material 30 that overlaps with the laminate strength adjustment layer 35 can be made to rupture, for example, the sealant layer 50. This makes it easier for steam to escape to the outside of the bag 10 through the rupture in the sealant layer 50. The high-temperature second elongation at break may be 170% or less, or 160% or less.

[0180] Furthermore, in the first type of packaging material 30, preferably, the high-temperature second breaking strength is 60 N or less in at least one direction. The breaking strength of the packaging material 30, especially in the flow direction, is a characteristic determined mainly by the mechanical properties of the base material 40 and the sealant layer 50, similar to the elongation at break, and the laminate strength adjustment layer 35 is not considered to contribute much to the breaking strength. Therefore, if the high-temperature second breaking strength of the packaging material 30 is 60 N or less, the high-temperature first breaking strength of the packaging material 30 is also expected to be 60 N or less.

[0181] Since the high-temperature first breaking strength of the packaging material 30 is 60N or less, after delamination of the laminate strength adjustment layer 35 occurs in the first region 33 of the packaging material 30 at the microwave heating temperature, a portion of the packaging material 30 that overlaps with the laminate strength adjustment layer 35 can be made to break, for example, the sealant layer 50. This makes it easier for steam to escape to the outside of the bag 10 through the break in the sealant layer 50.

[0182] Furthermore, in the first type of packaging material 30, preferably, the high-temperature second elongation at break is lower than the room-temperature second elongation at break in at least one direction. Also, in the first type of packaging material 30, preferably, the high-temperature second breaking strength is lower than the room-temperature second breaking strength. That is, the packaging material 30 preferably has the property of being less elongated or more easily broken at high temperatures compared to room temperatures. As a result, while maintaining a predetermined strength at room temperature, a portion of the packaging material 30 that overlaps with the laminate strength adjustment layer 35, for example, the sealant layer 50, can be broken at the microwave heating temperature. In the first type of packaging material 30, the room-temperature second elongation at break is, for example, more than 160%. Also, in the first type of packaging material 30, the room-temperature second breaking strength is, for example, more than 60N.

[0183] [Elongation and strength at break of the second type of packaging material] Next, we will describe the case in which the base material 40 of the packaging material 30 includes a first biaxially oriented plastic film 41 and a second biaxially oriented plastic film 42, where one of the first biaxially oriented plastic film 41 and the second biaxially oriented plastic film 42 mainly contains polyester, and the other of the first biaxially oriented plastic film 41 and the second biaxially oriented plastic film 42 mainly contains polyamide. In the following description, such a packaging material 30 will also be referred to as the second type of packaging material 30.

[0184] In the second type of packaging material 30, preferably, the high-temperature second elongation at break is 135% or less in at least one direction. If the high-temperature second elongation at break of the packaging material 30 is 135% or less, the high-temperature first elongation at break of the packaging material 30 is also expected to be 135% or less. The high-temperature second elongation at break may be 130% or less, 120% or less, 110% or less, or 100% or less.

[0185] Furthermore, in the second type of packaging material 30, preferably, the high-temperature second breaking strength is 60 N or less in at least one direction. If the high-temperature second breaking strength of the packaging material 30 is 60 N or less, it is expected that the high-temperature first breaking strength of the packaging material 30 will also be 60 N or less.

[0186] Furthermore, in the second type of packaging material 30, preferably, the high-temperature second elongation at break is lower than the room-temperature second elongation at break in at least one direction. Also, in the second type of packaging material 30, preferably, the high-temperature second breaking strength is lower than the room-temperature second breaking strength. In the second type of packaging material 30, the room-temperature second elongation at break is, for example, greater than 100%. Also, in the second type of packaging material 30, the room-temperature second breaking strength is, for example, greater than 60N, and may be greater than 65N.

[0187] [Elongation and strength at break of the third type of packaging material] Next, we will describe the case where the base material 40 of the packaging material 30 includes a biaxially oriented plastic film 44, and the biaxially oriented plastic film 44 mainly contains polyester. In the following description, such a packaging material 30 will also be referred to as the third type of packaging material 30.

[0188] In the third type of packaging material 30, preferably, the high-temperature second elongation at break is 125% or less in at least one direction. The high-temperature second elongation at break may be 120% or less, 110% or less, 100% or less, or 95% or less.

[0189] Furthermore, in the third type of packaging material 30, preferably, the high-temperature second breaking strength is 30 N or less in at least one direction.

[0190] Furthermore, in the third type of packaging material 30, preferably, the high-temperature second elongation at break is lower than the room-temperature second elongation at break in at least one direction. Also, in the third type of packaging material 30, preferably, the high-temperature second breaking strength is lower than the room-temperature second breaking strength. In the third type of packaging material 30, the room-temperature second elongation at break is, for example, greater than 100%. Also, in the third type of packaging material 30, the room-temperature second breaking strength is, for example, greater than 30N, may be greater than 35N, may be greater than 40N, or may be greater than 45N.

[0191] [Fourth type of packaging material: elongation at break and breaking strength] Next, we will describe the case where the base material 40 of the packaging material 30 includes a biaxially oriented plastic film 44, and the biaxially oriented plastic film 44 mainly contains polyamide. In the following description, such a packaging material 30 will also be referred to as the fourth type of packaging material 30.

[0192] In the fourth type of packaging material 30, preferably, the high-temperature second elongation at break is 155% or less in one direction and in a direction perpendicular to one direction, for example, in the flow direction and the perpendicular direction. The high-temperature second elongation at break may be 150% or less, 145% or less, 140% or less, or 135% or less.

[0193] Furthermore, in the fourth type of packaging material 30, preferably, the high-temperature second breaking strength is 60 N or less in at least one direction, for example, in at least one of the flow direction or the perpendicular direction. Furthermore, in the fourth type of packaging material 30, preferably, the high-temperature second breaking strength is 60 N or less in one direction and in a direction perpendicular to one direction, for example, in the flow direction and the perpendicular direction.

[0194] Furthermore, in the fourth type of packaging material 30, preferably, the high-temperature second breaking strength is lower than the room-temperature second breaking strength. In the fourth type of packaging material 30, the room-temperature second breaking elongation is, for example, greater than 130%. Also, in the fourth type of packaging material 30, the room-temperature second breaking strength is, for example, greater than 60N, may be greater than 65N, or may be greater than 70N.

[0195] [Lamination strength of packaging materials] Next, the preferred range of laminate strength for the packaging material 30 will be described. The preferred range of laminate strength for the packaging material 30 described below can be applied to any of the first to fourth types of packaging material 30 described above.

[0196] In the packaging material 30, preferably, the high-temperature second lamination strength is at least twice the high-temperature first lamination strength. In other words, preferably, the high-temperature lamination strength in the region where the lamination strength adjustment layer 35 is present is at least half the high-temperature lamination strength in the region where the lamination strength adjustment layer 35 is not present. This allows for proper delamination of the lamination strength adjustment layer 35 in the first region 33 of the packaging material 30 at the microwave heating temperature. The high-temperature second lamination strength of the packaging material 30 is, for example, 0.5 N or less. The high-temperature first lamination strength of the packaging material 30 is, for example, greater than 1.0 N.

[0197] Furthermore, in the packaging material 30, the room temperature second lamination strength may be twice or more than the room temperature first lamination strength, or it may be three times or more. The room temperature second lamination strength of the packaging material 30 is, for example, 2.0 N or less. Also, the room temperature first lamination strength of the packaging material 30 is, for example, greater than 4.0 N, may be greater than 5.0 N, or it may be greater than 6.0 N.

[0198] Method of heating the contents Next, an example of a method for heating the contents 19 contained in bag 10 will be described.

[0199] First, the bag 10 is placed inside the microwave oven with its bottom 12 facing downwards, allowing it to stand upright. Next, the contents are heated using the microwave oven. This raises the temperature of the contents 19, causing the moisture in the contents 19 to evaporate and increasing the pressure in the storage compartment 17.

[0200] According to this embodiment, the packaging material 30 constituting the gusset portion 20 of the bag 10 is provided with a laminate strength adjustment layer 35 that at least partially overlaps the steam vent seal portion 21b of the steam vent mechanism 25 located in the gusset portion 20. As a result, a steam flow path from the containment portion 17 to the unsealed portion 23 is easily formed in the portion of the packaging material 30 that overlaps with the steam vent seal portion 21b. This reduces the probability of steam escaping from locations other than the steam vent mechanism 25 or the bag 10 bursting. Steam that reaches the unsealed portion 23 is discharged to the outside through the penetration portion 22.

[0201] In this embodiment, preferably, the high-temperature second laminate strength of the packaging material 30 is twice or more the high-temperature first laminate strength. This allows the lamination strength adjustment layer 35 to be properly peeled off in the first region 33 of the packaging material 30 at the microwave heating temperature.

[0202] Furthermore, in this embodiment, preferably, the packaging material 30 has a low high-temperature second elongation at break or a high-temperature second breaking strength. For example, the high-temperature second elongation at break is lower than the room-temperature second elongation at break. Alternatively, the high-temperature second breaking strength may be lower than the room-temperature second breaking strength. Therefore, after delamination of the laminate strength adjustment layer 35 occurs, a portion of the packaging material 30 that overlaps with the laminate strength adjustment layer 35 can be made to break, for example, the sealant layer 50. This makes it easier for steam to escape to the outside of the bag 10 through the break in the sealant layer 50.

[0203] In the above-described embodiment, when heating the contents 19 contained in the bag 10, an example was shown in which the bag 10 was placed inside the microwave oven with the bottom 12 facing downwards, allowing it to stand upright. However, the invention is not limited to this, and the bag 10 may also be placed inside the microwave oven with the back film 15 facing downwards. In this case as well, since the surface film 14, which has a girdle portion 20 with a steam release mechanism 25, is located above the storage portion 17, it is possible to prevent the contents 19 from leaking out of the steam release mechanism 25.

[0204] Furthermore, when the bag 10 is placed inside the microwave oven with the back film 15 facing downwards, the contents are more easily heated uniformly compared to when the bag 10 is standing upright with the bottom 12 facing downwards. Also, because the area of ​​the bag 10 in contact with the microwave oven is large, even if the bag 10 softens due to heating, the level of the liquid inside is less likely to change. Therefore, during the heating process using a microwave oven, it is less likely that the contents will adhere to the inner surface of the surface film 14 above the liquid level of the contents. This prevents the phenomenon of the contents adhering to the inner surface of the surface film 14 being excessively overheated and causing holes to form in the surface film 14.

[0205] Variation It is possible to make various modifications to each of the embodiments described above. The following describes the modifications, referring to the drawings as needed. In the following description and the drawings used therein, parts that can be configured similarly to the embodiments described above will be given the same reference numerals as those used for the corresponding parts in the embodiments described above, and redundant explanations will be omitted. Furthermore, if it is clear that the effects and advantages obtained in the embodiments described above can also be obtained in the modifications, the explanation may be omitted.

[0206] (First variation) In the above-described embodiment, an example was shown in which the upper surface film 141 and the lower surface film 142 constituting the surface of the bag 10 are separate films that are not connected. However, the invention is not limited to this, and the upper surface film 141 and the lower surface film 142 constituting the surface of the bag 10 may be made of a single connected film. That is, the surface film 14 constituting the surface of the bag 10 may be made of a single film that is partially folded back to form the grommet portion 20.

[0207] Figure 25 is an exploded view showing an example of the film that constitutes the bag 10 described above as shown in Figure 1. Figure 26 is a cross-sectional view showing the bag 10 made of the film shown in Figure 25. In this modified example, the tip 202 of the gusset portion 20 is formed by folding back a single sheet of packaging material 30 that constitutes the surface film 14.

[0208] (Second variation) In the above-described embodiment, an example was shown in which the steam venting mechanism 25 provided in the girdle portion 20 of the bag 10 has a steam venting seal portion 21b that protrudes from the tip seal portion 21a toward the containment portion 17 side, and a non-seal portion 23. However, the configuration of the steam venting mechanism 20 is arbitrary, as long as it can connect the containment portion 17 and the outside of the bag 10 when the steam pressure exceeds a predetermined value.

[0209] Figure 27 is a front view showing the bag 10 according to this modified example. Figure 28 is a cross-sectional view of the bag 10 in Figure 27 along line XXVIII-XXVIII. In this modified example, the steam venting mechanism 25 has a penetration portion 22 that penetrates at least one of the upper surface film 141 or the lower surface film 142 at the tip seal portion 21a of the girdle seal portion 21 that extends along the tip portion 202. The penetration portion 22 may penetrate both the upper surface film 141 and the lower surface film 142, as shown in Figure 28. In addition, the laminate strength adjustment layer 35 of the packaging material 30 that constitutes the lower surface film 142 extends from the inner edge (the edge on the containment side) of the girdle seal portion 21 to at least the penetration portion 22. As shown in Figure 27, the laminate strength adjustment layer 35 of the packaging material 30 may extend from the inner edge (the edge on the containment side) of the girdle seal portion 21 to the outer edge (the edge on the external environment side).

[0210] In this modified example as well, when the laminate strength adjustment layer 35 peels off due to heating, the portion of the sealant layer 50 that overlaps with the laminate strength adjustment layer 35 is more likely to rupture. Therefore, steam from the containment section 17 can be easily released to the outside of the bag 10 through the penetration section 22 via the ruptured portion of the sealant layer 50 and the peeled portion of the laminate strength adjustment layer 35.

[0211] (Third variation) In the first modified example described above, an example was shown in which the non-seal portion 23 located at the gusset portion 20 of the bag 10 is surrounded by the tip seal portion 21a and the steam vent seal portion 21b. However, the invention is not limited to this, and as shown in Figure 29, the non-seal portion 23 may extend to the tip portion 202 of the gusset portion 20. Figure 30 is a cross-sectional view of the bag 10 in Figure 29 along the line XXX-XXX.

[0212] In this modified example, the packaging material 30 constituting the gusset portion 20 of the bag 10 is provided with a laminate strength adjustment layer 35 that at least partially overlaps the steam vent seal portion 21b of the steam vent mechanism 25 located in the gusset portion 20. As a result, a steam flow path from the containment portion 17 to the unsealed portion 23 is easily formed in the portion of the packaging material 30 that overlaps with the steam vent seal portion 21b. This reduces the probability of steam escaping from locations other than the steam vent mechanism 25 or the bag 10 bursting. Steam that reaches the unsealed portion 23 flows inside the unsealed portion 23 to the tip portion 202, and then is discharged to the outside from the tip portion 202.

[0213] (Fourth variation) In the embodiments and modifications described above, an example was shown in which the bag 10 is a gusset-type bag that includes a lower film 16 located between the surface film 14 and the back film 15 and is configured to be self-supporting. However, as long as the bag 10 has a gusset portion 20, the structure of the lower part 12 of the bag 10 is arbitrary. For example, as shown in Figures 31 to 33, the lower part 12 of the bag 10 may have a lower seal portion 12a formed by joining the inner surface of the lower surface film 142 of the surface film 14 and the inner surface of the back film 15. If the lower film 16 is not provided in the lower part 12 of the bag 10, the side with the opening 11b when filling the bag 10 with contents 19 is defined as the upper part 11, and the opposite side is defined as the lower part 12.

[0214] The bag 10 shown in Figure 31 is identical to the bag 10 of the embodiment described above shown in Figure 1, except that the lower part 12 of the bag 10 has a lower seal portion 12a formed by joining the inner surface of the lower surface film 142 of the surface film 14 and the inner surface of the back film 15. The bag 10 shown in Figure 32 is identical to the bag 10 of the second modified example described above shown in Figure 27, except that the lower part 12 of the bag 10 has a lower seal portion 12a formed by joining the inner surface of the lower surface film 142 of the surface film 14 and the inner surface of the back film 15. The bag 10 shown in Figure 33 is identical to the bag 10 of the third modified example described above shown in Figure 29, except that the lower part 12 of the bag 10 has a lower seal portion 12a formed by joining the inner surface of the lower surface film 142 of the surface film 14 and the inner surface of the back film 15.

[0215] While we have described several variations of the above-mentioned embodiment, it is naturally possible to combine and apply multiple variations as appropriate. [Examples]

[0216] Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the invention.

[0217] (Example A1) Low-density polyethylene (density 0.924 g / cm³) 3 A pellet with an MFR of 4.0 g / 10 min was fed into an extruder, and inflation molding was performed at a temperature of 150°C to produce a sealant film 51 with a thickness of 40 μm.

[0218] Next, the elongation at break and breaking strength of the sealant film 51 in the flow direction and perpendicular direction were measured in accordance with JIS K7127. A No.260 Strograph VG1F manufactured by Toyo Seiki Co., Ltd. was used as the measuring instrument. The test specimens were made by cutting the sealant film 51 into rectangular films with a width of 15 mm and a length of 150 mm. The distance between the pair of chucks holding the test specimen at the start of measurement was 50 mm, and the tensile speed was 200 mm / min. Measurements were performed in an environment with a temperature of 25°C and a relative humidity of 50% (hereinafter also referred to as the normal temperature environment), and in an environment with a temperature of 80°C and a relative humidity of 5% (hereinafter also referred to as the high temperature environment). As a result, in the normal temperature environment, the elongation at break of the sealant film 51 in the flow direction and perpendicular direction was 182.5% and 282.5%, respectively. Furthermore, in a normal temperature environment, the breaking strength of the sealant film 51 in the flow direction and perpendicular direction was 12.1 N and 7.3 N, respectively. In a high-temperature environment, the breaking elongation of the sealant film 51 in the flow direction and perpendicular direction was 90.1% and 150.1%, respectively. Furthermore, in a high-temperature environment, the breaking strength of the sealant film 51 in the flow direction and perpendicular direction was 6.7 N and 4.4 N, respectively.

[0219] (Example B1) A biaxially oriented PET film with a thickness of 12 μm was prepared as the first biaxially oriented plastic film 41 and the second biaxially oriented plastic film 42. The biaxially oriented PET film used had approximately the same tensile strength in the flow direction (MD) and the perpendicular direction (TD). A pattern layer 45 was formed on the inner surface of the first biaxially oriented plastic film 41. A laminate strength adjustment layer 35 was partially formed on the inner surface of the second biaxially oriented plastic film 42. The laminate strength adjustment layer 35 was made of a resin containing polyamide, nitrated cotton, and polyethylene wax. The thickness of the laminate strength adjustment layer 35 was 0.5 μm. A sealant film 51, as described in Example A1 above, was prepared as the sealant layer 50.

[0220] Next, a first biaxially oriented plastic film 41 with a pattern layer 45, a second biaxially oriented plastic film 42 with a laminate strength adjustment layer 35, and a sealant film 51 were laminated using a dry lamination method to produce the packaging material 30 shown in Figure 5. For the adhesive layer 43 and adhesive layer 61, a two-component polyurethane adhesive (main component: RU-40, curing agent: H-4) manufactured by Rock Paint Co., Ltd. was used. The thickness of the adhesive layer 43 was 3 μm, and the thickness of the adhesive layer 61 was 3 μm. The total thickness of the packaging material 30 was 72 μm.

[0221] Next, the elongation at break and the breaking strength were measured in the first region 33 and the second region 34 of the packaging material 30 in the flow direction and perpendicular direction. The method for measuring the elongation at break and the breaking strength was the same as in Example A1 described above, except that the film constituting the test specimen was the packaging material 30.

[0222] In a normal temperature environment, the elongation at break in the first region 33 of the packaging material 30 in the flow direction and perpendicular direction was 175.1% and 81.2%, respectively, and the elongation at break in the second region 34 was 164.6% and 131.9%, respectively. Also in a normal temperature environment, the breaking strength in the first region 33 of the packaging material 30 in the flow direction and perpendicular direction was 66.5 N and 83.0 N, respectively, and the breaking strength in the second region 34 was 65.7 N and 100.1 N, respectively. Also in a high temperature environment, the elongation at break in the first region 33 of the packaging material 30 in the flow direction and perpendicular direction was 158.8% and 70.8%, respectively, and the elongation at break in the second region 34 was 155.2% and 140.6%, respectively. Furthermore, in a high-temperature environment, the breaking strengths of the packaging material 30 in the first region 33 in the flow direction and perpendicular direction were 58.7 N and 69.6 N, respectively, and the breaking strengths in the second region 34 were 57.6 N and 79.2 N, respectively.

[0223] Thus, in Example B1, both the high-temperature first fracture elongation and the high-temperature second fracture elongation were 180% or less in the flow direction, specifically 160% or less. Furthermore, both the high-temperature first fracture strength and the high-temperature second fracture strength were 60N or less in the flow direction. In addition, in the flow direction, the high-temperature second fracture elongation was lower than the room-temperature second fracture elongation, and the high-temperature second fracture strength was lower than the room-temperature second fracture strength.

[0224] Furthermore, the lamination strength of the packaging material 30 in the flow direction was measured in accordance with JIS K7127. A No.260 Strograph VG1F manufactured by Toyo Seiki Co., Ltd. was used as the measuring instrument. For the test specimens, the first region 33 and the second region 34 of the packaging material 30 were cut into rectangular films with a width of 15 mm and a length of 150 mm. For the measurement, first, the base material 40 and the sealant layer 50 of the test specimen were peeled off along the long side for 15 mm from the tip of the test specimen. Next, as shown in Figure 22, the side of the test specimen with the sealant layer 50 was fixed to the support base 93 with a fixing device 95, and the already peeled portion of the base material 40 was gripped with the gripper 94 of the measuring instrument. Subsequently, the gripper 94 was pulled at a speed of 50 mm / min in a direction in which the surface of the base material 40 gripped by the gripper 94 formed a 180° angle with the surface of the sealant layer 50 fixed to the support base 93. The distance S between the gripping device 94 and the fixing device 95 in the direction of movement of the gripping device 94 was set to 30 mm when pulling was started, and the distance S when pulling was ended was set to 60 mm.

[0225] Under normal temperature conditions, the lamination strengths of the first region 33 and the second region 34 of the packaging material 30 were 1.5 N and 6.3 N, respectively. Furthermore, under high temperature conditions, the lamination strengths of the first region 33 and the second region 34 of the packaging material 30 were 0.5 N and 1.2 N, respectively.

[0226] Thus, in Example B1, the high-temperature second laminate strength of the packaging material 30 in the flow direction was more than twice that of the high-temperature first laminate strength. Furthermore, in the flow direction, the room-temperature second laminate strength of the packaging material 30 was more than twice that of the room-temperature first laminate strength, specifically more than four times.

[0227] (Comparative Example B1) The packaging material 30 was prepared in the same manner as in Example B1, except that TUX HC (thickness 40 μm) manufactured by Mitsui Chemicals Tohcello was used as the sealant film 51 constituting the sealant layer 50. The total thickness of the packaging material 30 was 72 μm.

[0228] Next, in the same manner as in Example B1, the elongation at break and breaking strength were measured in the second region 34 of the packaging material 30 in the flow direction and perpendicular direction. As a result, in a normal temperature environment, the elongation at break in the second region 34 of the packaging material 30 in the flow direction and perpendicular direction was 164.6% and 150.1%, respectively. Also in a normal temperature environment, the breaking strength in the second region 34 of the packaging material 30 in the flow direction and perpendicular direction was 65.7 N and 63.2 N, respectively. Furthermore, in a high temperature environment, the elongation at break in the second region 34 of the packaging material 30 in the flow direction and perpendicular direction was 183.2% and 170.1%, respectively. Also in a high temperature environment, the breaking strength in the second region 34 of the packaging material 30 in the flow direction and perpendicular direction was 61.1 N and 58.4 N, respectively.

[0229] Furthermore, in the same manner as in Example B1, the lamination strength in the second region 34 of the packaging material 30 was measured in the flow direction. As a result, the lamination strength in the second region 34 of the packaging material 30 was 5.7 N in a room temperature environment. In a high-temperature environment, the lamination strength in the second region 34 of the packaging material 30 was 1.1 N.

[0230] (Example B2) As the first biaxially stretched plastic film 41, a biaxially stretched nylon film (thickness 15 μm) was used, and a packaging material 30 having the layer structure shown in FIG. 5 was produced in the same manner as in Example B1, except for this. The thickness of the entire packaging material 30 was 75 μm.

[0231] Subsequently, in the same manner as in Example B1, the elongation at break and the breaking strength were measured in the first region 33 and the second region 34 of the packaging material 30 in the flow direction and the vertical direction. As a result, at room temperature environment, the elongation at break in the first region 33 of the packaging material 30 in the flow direction and the vertical direction were 115.0% and 106.7% respectively, and the elongation at break in the second region 34 were 100.2% and 118.4% respectively. Also, at room temperature environment, the breaking strength in the first region 33 of the packaging material 30 in the flow direction and the vertical direction were 66.7 N and 90.1 N respectively, and the breaking strength in the second region 34 were 67.0 N and 97.3 N respectively. Also, in a high temperature environment, the elongation at break in the first region 33 of the packaging material 30 in the flow direction and the vertical direction were 97.8% and 125.2% respectively, and the elongation at break in the second region 34 were 93.0% and 110.2% respectively. Also, in a high temperature environment, the breaking strength in the first region 33 of the packaging material 30 in the flow direction and the vertical direction were 56.4 N and 75.6 N respectively, and the breaking strength in the second region 34 were 55.7 N and 76.5 N respectively.

[0232] Thus, in Example B2, in the flow direction, both the high temperature first elongation at break and the high temperature second elongation at break were 135% or less, specifically 100% or less. Also, in the flow direction, both the high temperature first breaking strength and the high temperature second breaking strength were 60 N or less. Also, in the flow direction, the high temperature second elongation at break was lower than the room temperature second elongation at break, and the high temperature second breaking strength was lower than the room temperature second breaking strength.

[0233] (Comparative Example B2) A packaging material 30 was produced in the same manner as in Example B2, except that TUX HC (thickness: 40 μm) manufactured by Mitsui Chemicals Toagosei Co., Ltd. was used as the sealant layer 50. The thickness of the entire packaging material 30 was 75 μm.

[0234] Subsequently, in the same manner as in Example B1, the elongation at break and the breaking strength were measured in the second region 34 of the packaging material 30 in the flow direction and the perpendicular direction. As a result, at normal temperature, the elongation at break in the second region 34 of the packaging material 30 in the flow direction and the perpendicular direction was 102.3% and 110.1% respectively. Also, at normal temperature, the breaking strength in the second region 34 of the packaging material 30 in the flow direction and the perpendicular direction was 66.2 N and 95.1 N respectively. Also, in a high-temperature environment, the elongation at break in the second region 34 of the packaging material 30 in the flow direction and the perpendicular direction was 138.1% and 143.2% respectively. Also, in a high-temperature environment, the breaking strength in the second region 34 of the packaging material 30 in the flow direction and the perpendicular direction was 60.1 N and 74.2 N respectively.

[0235] (Example B3) Biaxially stretched plastic films 44 with a thickness of 12 μm each were prepared as biaxially stretched PET films. As with Example B1, biaxially stretched PET films with substantially the same tensile strength in the flow direction (MD) and the perpendicular direction (TD) were used. Also, a pattern layer 45 was formed on the inner surface of the biaxially stretched plastic film 44, and a laminate strength adjustment layer 35 was partially formed on the inner surface of the pattern layer 45. As with Example B1, a resin containing polyamide, nitrocellulose, and polyethylene wax was used as the laminate strength adjustment layer 35. The thickness of the laminate strength adjustment layer 35 was 0.5 μm. Also, as the sealant layer 50, the sealant film 51 described in Example A1 above was prepared.

[0236] Next, a biaxially oriented plastic film 44 and a sealant film 51, each having a pattern layer 45 and a laminate strength adjustment layer 35, were laminated using a dry lamination method to produce the packaging material 30 shown in Figure 10. For the adhesive layer 61, a two-component polyurethane adhesive (main component: RU-40, curing agent: H-4) manufactured by Rock Paint Co., Ltd. was used. The thickness of the adhesive layer 61 was 3 μm. The total thickness of the packaging material 30 was 56 μm.

[0237] Next, in the same manner as in Example B1, the elongation at break and breaking strength were measured in the first region 33 and the second region 34 of the packaging material 30 in the flow direction and perpendicular direction. As a result, at room temperature, the elongation at break in the first region 33 of the packaging material 30 in the flow direction and perpendicular direction was 132.7% and 78.0%, respectively, and the elongation at break in the second region 34 was 102.5% and 96.2%, respectively. Also at room temperature, the breaking strength in the first region 33 of the packaging material 30 in the flow direction and perpendicular direction was 49.6 N and 43.7 N, respectively, and the breaking strength in the second region 34 was 47.0 N and 45.0 N, respectively. Furthermore, in a high-temperature environment, the elongation at break in the first region 33 of the packaging material 30 in the flow direction and perpendicular direction was 120.5% and 56.6%, respectively, and the elongation at break in the second region 34 was 91.3% and 49.8%, respectively. In addition, in a high-temperature environment, the breaking strength in the first region 33 of the packaging material 30 in the flow direction and perpendicular direction was 29.9 N and 27.6 N, respectively, and the breaking strength in the second region 34 was 25.9 N and 28.5 N, respectively.

[0238] Thus, in Example B3, both the high-temperature first fracture elongation and the high-temperature second fracture elongation were 125% or less in the flow direction. Furthermore, the high-temperature second fracture elongation was 95% or less in the flow direction. Also, both the high-temperature first fracture strength and the high-temperature second fracture strength were 30 N or less in the flow direction. Furthermore, in the flow direction, the high-temperature second fracture elongation was lower than the room-temperature second fracture elongation, and the high-temperature second fracture strength was lower than the room-temperature second fracture strength.

[0239] Furthermore, in the same manner as in Example B1, the lamination strength in the first region 33 and the second region 34 of the packaging material 30 was measured in the flow direction. As a result, at room temperature, the lamination strengths in the first region 33 and the second region 34 of the packaging material 30 were 1.7 N and 6.1 N, respectively. In a high-temperature environment, the lamination strengths in the first region 33 and the second region 34 of the packaging material 30 were 0.4 N and 1.4 N, respectively.

[0240] Thus, in Example B3, the high-temperature second laminate strength of the packaging material 30 in the flow direction was more than twice, specifically more than three times, the high-temperature first laminate strength. Furthermore, in the flow direction, the room-temperature second laminate strength of the packaging material 30 was more than twice, specifically more than three times, the room-temperature first laminate strength.

[0241] (Comparative Example B3-1) The packaging material 30 was prepared in the same manner as in Example B3, except that TUX HC (thickness 40 μm) manufactured by Mitsui Chemicals Tohcello was used as the sealant layer 50. The total thickness of the packaging material 30 was 56 μm.

[0242] Next, in the same manner as in Example B1, the elongation at break and breaking strength were measured in the second region 34 of the packaging material 30 in the flow direction and perpendicular direction. As a result, in a normal temperature environment, the elongation at break in the second region 34 of the packaging material 30 in the flow direction and perpendicular direction was 102.5% and 95.1%, respectively. Also in a normal temperature environment, the breaking strength in the second region 34 of the packaging material 30 in the flow direction and perpendicular direction was 47.9 N and 44.3 N, respectively. Furthermore, in a high temperature environment, the elongation at break in the second region 34 of the packaging material 30 in the flow direction and perpendicular direction was 142.1% and 113.1%, respectively. Also in a high temperature environment, the breaking strength in the second region 34 of the packaging material 30 in the flow direction and perpendicular direction was 34.9 N and 34.2 N, respectively.

[0243] Furthermore, in the same manner as in Example B1, the lamination strength in the second region 34 of the packaging material 30 was measured in the flow direction. As a result, the lamination strength in the second region 34 of the packaging material 30 was 5.4 N in a room temperature environment. In a high-temperature environment, the lamination strength in the second region 34 of the packaging material 30 was 1.2 N.

[0244] (Comparative Example B3-2) The packaging material 30 was prepared in the same manner as in Example B3, except that Toyobo's Rix L6102 (thickness 40 μm) was used as the sealant layer 50. The total thickness of the packaging material 30 was 56 μm.

[0245] Next, in the same manner as in Example B1, the elongation at break and breaking strength were measured in the second region 34 of the packaging material 30 in the flow direction and perpendicular direction. As a result, in a normal temperature environment, the elongation at break in the second region 34 of the packaging material 30 in the flow direction and perpendicular direction was 104.3% and 94.2%, respectively. Also in a normal temperature environment, the breaking strength in the second region 34 of the packaging material 30 in the flow direction and perpendicular direction was 40.1 N and 38.7 N, respectively. Furthermore, in a high temperature environment, the elongation at break in the second region 34 of the packaging material 30 in the flow direction and perpendicular direction was 126.2% and 110.2%, respectively. Also in a high temperature environment, the breaking strength in the second region 34 of the packaging material 30 in the flow direction and perpendicular direction was 32.4 N and 30.3 N, respectively.

[0246] (Example B4) Except for using a biaxially oriented nylon film (15 μm thick) as the biaxially oriented plastic film 44, a packaging material 30 having the layer structure shown in Figure 10 was prepared in the same manner as in Example B3. The total thickness of the packaging material 30 was 59 μm.

[0247] Next, in the same manner as in Example B1, the elongation at break and breaking strength were measured in the second region 34 of the packaging material 30 in the flow direction and perpendicular direction. As a result, in a normal temperature environment, the elongation at break in the second region 34 of the packaging material 30 in the flow direction and perpendicular direction was 110.3% and 90.3%, respectively. Also in a normal temperature environment, the breaking strength in the second region 34 of the packaging material 30 in the flow direction and perpendicular direction was 65.4 N and 63.2 N, respectively. Furthermore, in a high temperature environment, the elongation at break in the second region 34 of the packaging material 30 in the flow direction and perpendicular direction was 133.0% and 135.0%, respectively. Also in a high temperature environment, the breaking strength in the second region 34 of the packaging material 30 in the flow direction and perpendicular direction was 57.6 N and 55.4 N, respectively.

[0248] Thus, in Example B4, the high-temperature second fracture elongation was 155% or less in both the flow direction and the perpendicular direction, specifically 135% or less. Furthermore, the high-temperature second fracture strength was 60 N or less in both the flow direction and the perpendicular direction.

[0249] (Comparative example B4) The packaging material 30 was prepared in the same manner as in Example B4, except that the sealant film 51 described in Comparative Example A1 above was used as the sealant layer 50. The total thickness of the packaging material 30 was 54 μm.

[0250] Subsequently, in the same manner as in the case of Example B1, the elongation at break and the breaking strength were measured in the second region 34 of the packaging material 30 in the flow direction and the vertical direction. As a result, at room temperature, the elongation at break in the second region 34 of the packaging material 30 in the flow direction and the vertical direction was 119.0% and 130.2% respectively. Also, at room temperature, the breaking strength in the second region 34 of the packaging material 30 in the flow direction and the vertical direction was 70.9 N and 68.6 N respectively. Further, in a high-temperature environment, the elongation at break in the second region 34 of the packaging material 30 in the flow direction and the vertical direction was 158.2% and 130.4% respectively. Also, in a high-temperature environment, the breaking strength in the second region 34 of the packaging material 30 in the flow direction and the vertical direction was 48.2 N and 50.4 N respectively.

[0251] The measurement results of the elongation at break and the breaking strength in Examples B1 and B2 and Comparative Examples B1 and B2 are shown together with the layer structure of the packaging material 30 in FIG. 32. Also, the measurement results of the elongation at break and the breaking strength in Examples B3 and B4 and Comparative Examples B3-1, B3-2 and B4 are shown together with the layer structure of the packaging material 30 in FIG. 33. In the column of "layer structure", "low-density polyethylene 1" means the sealant film (thickness: 40 μm) shown in Example A1. Also, "low-density polyethylene 2" means TUX HC (thickness: 40 μm) manufactured by Mitsui Chemicals Toatsu Chemicals, Inc. Also, "low-density polyethylene 3" means Lix L6102 (thickness: 40 μm) manufactured by Toyobo Co., Ltd.

Explanation of Signs

[0252] 10 bag 11 upper part 11a upper seal part 11b opening part 12 lower part 12a lower seal part 13 side part 13a side seal part 14 surface film 141 upper surface film 142 lower surface film 15 lower surface film 16 Lower film 17. Detention Unit 19 Contents 20 Gassho Club 201 Base 202 Tip 21. Joint sealing section (extending along the tip) 21a Tip sealing section 21b Steam vent seal section 22 Penetration section 23 Non-sealed portion 25 Steam venting mechanism 26 Non-sealed portion 27 Penetration section 28 Easy-to-open means 29 Notches 30 Packaging materials 31 Exterior 32 Inner self 33 First area 34 Second area 35. Laminate strength adjustment layer 40 Base material 41. First biaxially oriented plastic film 42. Second biaxially oriented plastic film 43 Adhesive layer 44 Biaxially oriented plastic film 45 Pattern Layers 50 sealant layer 51 Sealant film 61 Adhesive layer 62 Anchor Coat Layer

Claims

1. A bag having a front and back surface formed from packaging material, The packaging material has at least a base material and a sealant layer, arranged in order from the outer side to the inner side. The substrate includes at least one biaxially oriented plastic film, The sealant layer contains polyethylene as its main component, The packaging material constituting the surface includes an upper surface film located at least at the top of the bag, and a lower surface film located at least at the bottom of the bag and partially overlapping with the upper surface film. At least one of the packaging material constituting the upper surface film and the packaging material constituting the lower surface film further comprises a laminate strength adjusting layer partially located between the substrate and the sealant layer. The aforementioned bag is The bag comprises an outer edge sealing portion that extends along the outer edge and joins the inner surfaces of the packaging materials together, and a gusset sealing portion that joins the inner surface of the upper surface film and the inner surface of the lower surface film in the gusset portion where the upper surface film and the lower surface film are overlapped, The laminate strength adjustment layer is positioned so as to at least partially overlap the gable seal portion. The aforementioned gable seal portion includes a tip seal portion extending along the tip of the gable portion and a steam vent seal portion protruding from the tip seal portion toward the base of the gable portion. The gable portion has a non-seal portion (23) isolated from the storage portion of the bag by the steam vent seal portion, and a plurality of non-seal portions (26) isolated from the non-seal portion (23) and the storage portion and arranged in a first direction. The first direction is the direction in which the pair of sides of the bag face each other. The laminate strength adjustment layer is positioned so as to at least partially overlap the steam vent seal portion. The bag has a through portion consisting of a cut line that penetrates the packaging material in the unsealed portion (23) which is isolated from the storage portion of the bag by the steam vent seal portion, The bag wherein the laminate strength adjustment layer extends from the inner edge to the outer edge of the steam vent seal portion.

2. The bag according to claim 1, wherein the unsealed portion (23), which is isolated from the storage portion of the bag by the steam-venting seal portion, extends to the tip of the gable portion.

3. The bag according to claim 1 or 2, wherein the bag has a through portion (27) in the non-seal portion (26) that is a cut line that penetrates the packaging material.

4. The bag according to any one of claims 1 to 3, comprising a lower film located between the lower surface film and the back film, and constituting the lower part of the bag.

5. The bag according to claim 4, further comprising an easy-opening means formed on the side edge of the bag between the girdle portion and the lower film.

6. The bag according to any one of claims 1 to 5, wherein the biaxially oriented plastic film contained in the base material is only two.

7. The bag according to claim 6, wherein the two biaxially oriented plastic films contain polyester as the main component.

8. The bag according to claim 6, wherein one of the two biaxially oriented plastic films contains polyester as the main component, and the other of the two biaxially oriented plastic films contains polyamide as the main component.

9. The substrate contains only one biaxially oriented plastic film. The bag according to any one of claims 1 to 5, wherein the biaxially oriented plastic film mainly comprises polyester.

10. The substrate contains only one biaxially oriented plastic film. The bag according to any one of claims 1 to 5, wherein the biaxially oriented plastic film mainly comprises polyamide.

11. The bag according to any one of claims 1 to 10, wherein the polyethylene in the sealant layer comprises low-density polyethylene, and / or linear low-density polyethylene in which the α-olefin is butene.

12. The bag according to any one of claims 1 to 11, wherein the laminate strength adjusting layer is composed of a resin composition comprising polyamide, cellulose, and an ethylene-vinyl acetate copolymer resin or polyolefin wax.

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