Package, and laminate constituting package

Abstract

To provide a package for microwave cooking configured so that vapor can be properly extracted from a vapor extraction part, and a laminate constituting the package.SOLUTION: A package for microwave cooking is composed of a laminate in which a polyethylene terephthalate film and a sealant layer are provided in this order. The sealant layer has a sea-island structure therein. In a processed image obtained by subjecting an image of a cross section parallel to a machine direction of the sealant layer, observed with a scanning-type probe microscope to contrast highlighting processing, mist removal processing, binarization processing and shadow processing, an average value of areas of an island part is 0.153 μm2 or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a package and a laminate that constitutes the package. [Background technology]

[0002] Patent Document 1 discloses a package for microwave cooking that is made of a laminate including a polyethylene terephthalate film and a sealant layer. The package is provided with a steam vent that opens as a steam port when the internal pressure reaches or exceeds a predetermined pressure. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-130141 Summary of the Invention [Problem to be solved by the invention]

[0004] In a package for microwave cooking such as that described in Patent Document 1, depending on the structure of the laminate that constitutes the package, steam may not escape from the steam release section even when the internal pressure of the package reaches or exceeds a predetermined pressure. The present disclosure provides a package for microwave cooking that allows steam to escape appropriately from the steam release section, and a laminate that constitutes the package. [Means for solving the problem]

[0005] One aspect of the present disclosure is a package for microwave cooking that is composed of a laminate including a polyethylene terephthalate film and a sealant layer. The sealant layer has an internal sea-island structure, and in a processed image obtained by contrast-enhancing, matting, binarizing, and shadow-processing an image of a cross section of the sealant layer parallel to the machine direction observed with a scanning probe microscope, the average area of ​​the islands is 0.153 μm. 2 The sealant layer has an average island area of ​​0.153 μm in the processed image. 2The above-described sea-island structure allows steam to be properly released from the steam release section of the package for microwave cooking.

[0006] Another aspect of the present disclosure is a package for microwave cooking that is composed of a laminate including a polyethylene terephthalate film and a sealant layer. The sealant layer has an internal sea-island structure, and in a processed image obtained by contrast-enhancing, matting, binarizing, and shadow-processing an image of a cross section of the sealant layer parallel to the machine direction observed with a scanning probe microscope, the average longitudinal length of the island portions is 1.658 μm or more. By having the sealant layer have a sea-island structure in which the average longitudinal length of the island portions is 1.658 μm or more in the processed image, steam can be properly released from the steam vent portion of the package for microwave cooking.

[0007] Another aspect of the present disclosure is a laminate that constitutes the above-described package for microwave cooking, and that provides the same effects as the above-described package. [Effects of the Invention]

[0008] The present disclosure can provide a package for microwave cooking that allows steam to escape appropriately through a steam release section, and a laminate that constitutes the package. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a plan view showing an example of a packaging body according to an embodiment. [Figure 2] FIG. 2 is a plan view showing an example of the packaging bag shown in FIG. [Figure 3] FIG. 3 is a partially enlarged view showing another example of the steam release section of the packaging bag shown in FIG. [Figure 4] FIG. 4 is a cross-sectional view showing an example of the laminate shown in FIG. [Figure 5]Figure 5(A) is an example of an image opened in Image J. Figure 5(B) is an example of an image that has undergone contrast enhancement processing. Figure 5(C) is an example of an image that has undergone defocusing processing. Figure 5(D) is an example of an image that has undergone binarization processing. Figure 5(E) is an example of an image that has undergone shadow processing. [Figure 6] Figure 6(A) is a graph plotting the average island area for each sample. Figure 6(B) is a graph plotting the average island length (approximated as a rectangle) for each sample. Figure 6(C) is a graph plotting the average island length (approximated as an ellipse) for each sample. [Figure 7] FIG. 7 is a graph plotting the average value of the ellipse slope for each sample. DETAILED DESCRIPTION OF THE INVENTION

[0010] The following describes embodiments of the present disclosure. The following embodiments are examples for explaining the present disclosure and are not intended to limit the present disclosure to the following content. The upper or lower limit of a numerical range specified in this disclosure may be replaced with any value shown in the examples. The upper and lower limit values ​​individually described may be combined arbitrarily. Unless otherwise specified, the materials or components exemplified in this disclosure may be used alone or in combination of two or more. In the description, the same elements or elements having the same functions are denoted by the same reference numerals, and redundant explanations are omitted. Positional relationships such as up, down, left, and right used in the description are based on the positional relationships shown in the drawings, unless otherwise specified.

[0011] [Packaging composition] FIG. 1 is a plan view showing an example of a packaging body according to one embodiment. The packaging body 1 is a packaging body for microwave cooking. Microwave cooking means cooking the contents inside the packaging body by heating in a microwave oven. The packaging body 1 includes a packaging bag 2 and a content 21 accommodated in an accommodation section 20 of the packaging bag 2. The packaging bag 2 is composed of two laminates 10a and 10b that form the side surfaces and a laminate 10c that forms the bottom surface. The laminates 10a, 10b, and 10c have the same structure. The laminate 10a is a laminate that includes a polyethylene terephthalate film and a sealant layer. Details of the laminates will be described later.

[0012] The packaging bag 2 has a top seal portion 22 at the top end, side seal portions 23, 24 at both side ends, and bottom seal portions 25, 26 at the bottom end. The top seal portion 22 and the side seal portions 23, 24 are formed by heat-sealing the sealant layers at the respective ends of the laminates 10a, 10b in an overlapping state. The bottom seal portion 25 is formed by heat-sealing the sealant layers at the respective ends of the laminates 10a, 10c in an overlapping state. The bottom seal portion 26 is formed by heat-sealing the sealant layers at the respective ends of the laminates 10b, 10c in an overlapping state. The dotted portions in FIG. 1 indicate the seal portions formed by heat sealing. The portions other than the sealed portions are non-sealed portions where the laminates 10a, 10b, 10c are not heat-sealed. The laminates 10a, 10b, and 10c that make up the packaging bag 2 form an internal space (storage section 20) that stores an item 21 by sealing the respective seal sections. In this way, the storage section 20 is surrounded by the laminates 10a, 10b, and 10c.

[0013] FIG. 2 is a plan view showing an example of the packaging bag shown in FIG. 1. The packaging body 1 may be manufactured using the packaging bag 2A shown in FIG. 2. In the packaging bag 2A, the upper end 22a of the laminate 10a (10b) is not heat-sealed. Before the upper end 22a is heat-sealed, the contents 21 are filled through the opening formed at the upper end 22a, and then the upper end 22a of the laminate 10a (10b) is heat-sealed. After the contents 21 are filled, the upper end seal portion 22 is formed, thereby obtaining the packaging body 1 shown in FIG. 1, in which the contents 21 are sealed in the storage portion 20 of the packaging bag 2. The position where the opening for filling the contents 21 is formed is not limited to the upper end 22a, and may be a side portion or a bottom portion.

[0014] A pair of notches 27, 27 may be provided in the side edge seal portions 23, 24 of the packaging bag 2. A planned tear line (not shown) may be provided connecting the pair of notches 27, 27. After heating the packaging body 1 in a microwave oven, the end user can open the packaging body 1 from one of the notches 27 along the planned tear line and remove the heated contents 21. The contents 21 are not particularly limited. The contents 21 may contain not only water but also oils and fats. Examples of the contents 21 include foods such as curry, stew, soup, simmered dishes, and grilled dishes.

[0015] The side edge seal portions 24 include steam release portions 28 configured to form steam vents that communicate between the storage portion 20 and the outside of the packaging bag 2 when the pressure in the storage portion 20 of the packaging bag 2 increases. The steam release portions 28 protrude toward the center of the packaging bag 2. When the contents 21 in the storage portion 20 are heated in a microwave oven and steam is generated, the storage portion 20 expands. The forces applied to the top end seal portion 22, the side edge seal portions 23, 24, and the bottom end seal portions 25, 26 as the storage portion 20 expands increase the closer the distance from the center. Therefore, large tensile stresses are applied to the steam release portions 28 that protrude toward the center as the contents 21 are heated.

[0016] When the pressure in the storage section 20 reaches or exceeds a predetermined value, the side edge seal section 24 peels away from the inner edge in the steam release section 28, connecting the storage section 20 to the outside of the packaging bag 2 (packaging body 1). Steam then escapes to the outside through a steam vent hole (steam release hole) formed in the steam release section 28. The steam release section 28 has the function of forming a steam vent hole when the pressure in the storage section 20 rises, thereby preventing the packaging bag 2 (packaging body 1) from rupturing.

[0017] In the steam release section 28, a non-sealed section 29 is provided on the outside of the side edge sealed section 24. The seal width of the side edge sealed section 24 in the steam release section 28 is smaller than the seal width of the side edge sealed section 24 other than the steam release section 28. Therefore, when the pressure inside the accommodating section 20 increases, a steam vent port that connects the accommodating section 20 to the outside is appropriately formed in the steam release section 28. In order to appropriately release (exhaust) steam from the accommodating section 20 to the outside, the non-sealed section 29 may be provided with a through-hole that penetrates in the stacking direction of the stacks 10a, 10b.

[0018] The minimum seal width of the side edge seal portion 24 in the steam release portion 28 may be 1 to 5 mm, or may be 2 to 4 mm. In this case, steam can be appropriately released during heating in a microwave oven while maintaining hermetic sealing. The shape and position of the steam release portion 28 are not particularly limited. FIG. 3 is a partially enlarged view showing another example of the steam release portion of the packaging bag shown in FIG. 1. As shown in FIG. 3, the steam release portion 28 may protrude toward the center CE of the packaging bag 2. In a modified example, the steam release portion 28 may be provided in the upper end seal portion 22. Regardless of the shape and position, the minimum seal width of the steam release portion 28 may be within the above-mentioned numerical range. The steam release portion 28 may be provided in multiple locations.

[0019] The packaging bag 2 (packaging body 1) is subjected to a retort treatment in which it is heated for several minutes or more in a hot water spray at over 100° C. The packaging body 1 is sterilized by the retort treatment and can be stored at room temperature for a long period of time.

[0020] The packaging bag 2 does not need to include the laminate 10c that forms the bottom surface. In this case, the packaging bag 2 is formed by heat-sealing the sealant layers at the ends of the two laminates 10a and 10b in a state where they are overlapped.

[0021] [Laminate structure] Fig. 4 is a cross-sectional view showing an example of the laminate shown in Fig. 1. As shown in Fig. 4, the laminate 10 has a sealant layer 16 on one side of a polyethylene terephthalate (PET) film 11. A nylon 6 film 14 is interposed between the PET film 11 and the sealant layer 16. A first adhesive layer 13 is interposed between the PET film 11 and the nylon 6 film 14. A second adhesive layer 15 is interposed between the nylon 6 film 14 and the sealant layer 16. A printed layer 12 is interposed between the PET film 11 and the first adhesive layer 13. The laminate 10 only needs to include the PET film 11 and the sealant layer 16, and the printed layer 12, the first adhesive layer 13, the nylon 6 film 14, and / or the second adhesive layer 15 may be included as needed.

[0022] The thickness of the PET film 11 is not particularly limited and may be 9 to 25 μm, 10 to 20 μm, or 10 to 15 μm. The thickness of the PET film 11 may be adjusted depending on the application or desired properties.

[0023] The PET content in the PET film 11 may be 50% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more of the total amount of the PET film 11.

[0024] A commercially available PET film 11 can be used. The PET film 11 may be a stretched film or an unstretched film. It is believed that the degree of crystal orientation in a polymer film is improved by stretching the film. When a stretched film is used, the number of oriented crystals in the film increases, improving puncture strength. The stretching direction may be the MD direction or the TD direction. The stretching method may be any method that can provide a dimensionally stable film, such as uniaxial stretching, biaxial stretching, or a tubular method. From the viewpoint of further improving puncture strength, a biaxially stretched film may be used as the PET film 11. The biaxially stretched film may be a biaxially stretched film obtained by a simultaneous biaxial stretching method or a sequential biaxial stretching method.

[0025] The thickness of the nylon 6 film 14 is not particularly limited and may be 10 to 25 μm, 10 to 20 μm, or 12 to 17 μm. The thickness of the nylon 6 film 14 may be adjusted depending on the application or desired properties.

[0026] The nylon 6 film 14 is a polymer film containing nylon 6, which is a synthetic polymer containing polyamide. The polyamide content in the nylon 6 film 14 may be 50% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more of the total amount of the nylon 6 film 14. Since the nylon 6 film 14 has excellent puncture strength and flexibility, the inclusion of the nylon 6 film 14 can further improve the puncture strength and flexibility of the laminate 10.

[0027] A commercially available nylon 6 film 14 can be used. The nylon 6 film 14 may be a stretched film or an unstretched film. When a stretched film is used, the amount of oriented crystals in the film increases, improving puncture strength. The stretching direction may be either the MD direction or the TD direction. The stretching method may be any method that can provide a dimensionally stable film, such as uniaxial stretching, biaxial stretching, or a tubular method. The biaxially stretched film obtained by biaxial stretching may be obtained by a simultaneous biaxial stretching method, or may be obtained by a sequential biaxial stretching method from the viewpoint of orienting the internal molecules and improving puncture strength. A nylon 6 film 14 obtained by a tubular method may be used from the viewpoint of sufficiently orienting the internal molecules of the nylon 6 film 14 and further improving puncture strength.

[0028] The sealant layer 16 is a layer that provides heat-sealing properties to the laminate 10. The sealant layer 16 may be made of, for example, a thermoplastic resin. Examples of the thermoplastic resin include polyolefin-based resins such as low-density polyethylene (LDPE), medium-density polyethylene (MDPE), linear low-density polyethylene (LLDPE), ethylene-vinyl acetate copolymer (EVA), and ethylene-α-olefin copolymer; ethylene-based resins such as ethylene-(meth)acrylic acid copolymer; blends of polyethylene and polybutene; homopolypropylene resin (PP); propylene-ethylene random copolymers, propylene-ethylene block copolymers, and propylene-α-olefin copolymers; and polypropylene-based resins. The sealant layer 16 may also be made of a mixture of two or more of these thermoplastic resins. The thermoplastic resin can be appropriately selected depending on the intended use.

[0029] The resin constituting the sealant layer 16 may contain various additives such as a flame retardant, a slip agent, an antiblocking agent, an antioxidant, a light stabilizer, and a tackifier.

[0030] A commercially available sealant layer can be used as the sealant layer 16. The sealant layer 16 may be an unstretched film (for example, an unstretched polypropylene film) from the viewpoint of improving the sealing property by heat sealing. The thickness of the sealant layer 16 can be adjusted depending on the mass of the contents or the shape of the packaging bag, and may be approximately 10 to 100 μm.

[0031] The first adhesive layer 13 is interposed between the PET film 11 and the nylon 6 film 14. The second adhesive layer 15 is interposed between the nylon 6 film 14 and the sealant layer 16. The materials for the first adhesive layer 13 and the second adhesive layer 15 are, for example, polyester-isocyanate resin, urethane resin, polyether resin, etc. The first adhesive layer 13 firmly bonds the PET film 11 and the nylon 6 film 14. The second adhesive layer 15 firmly bonds the nylon 6 film 14 and the sealant layer 16. The materials for the first adhesive layer 13 and the second adhesive layer 15 may be the same or different from each other.

[0032] The thicknesses of the first adhesive layer 13 and the second adhesive layer 15 are not particularly limited and may be, for example, 0.5 to 5.0 μm, or 2 to 3 μm. When the thickness of the first adhesive layer 13 is 0.5 μm or more, the adhesion between the PET film 11 and the nylon 6 film 14 can be improved. When the thickness of the second adhesive layer 15 is 0.5 μm or more, the adhesion between the nylon 6 film 14 and the sealant layer 16 can be improved. When the thickness of the first adhesive layer 13 and the second adhesive layer 15 is 5.0 μm or less, the recyclability of the laminate 10 can be improved. The thickness of the first adhesive layer 13 and the second adhesive layer 15 may be the same as or different from each other.

[0033] The first adhesive layer 13 and the second adhesive layer 15 are layers that bond two adjacent layers together when forming the laminate 10. The laminate 10 can be formed by laminating a nylon 6 film 14 onto a PET film 11 and then laminating a sealant layer 16 to the nylon 6 film 14. Methods for forming the laminate 10 include dry lamination, which uses an adhesive such as a one-component or two-component curing urethane adhesive, non-solder dry lamination, and extrusion lamination, which uses a thermoplastic resin as described above that is heated and melted and extruded into a curtain shape for lamination. The adhesive used to laminate the nylon 6 film 14 to the PET film 11 forms the first adhesive layer 13 as shown in FIG. 4. The adhesive used to laminate the sealant layer 16 to the nylon 6 film 14 forms the second adhesive layer 15 as shown in FIG. 4.

[0034] A printed layer 12 can be provided on the surface of the PET film 11 facing the nylon 6 film 14. The printed layer 12 is provided in a position visible from the outside of the laminate for the purpose of displaying information about the contents, identifying the contents, or improving the design of the packaging bag. The printing method and printing ink are not particularly limited, and are appropriately selected from known printing methods and printing inks taking into consideration printability on the film, design such as color tone, adhesion, and safety as a food container. Examples of printing methods that can be used include gravure printing, offset printing, gravure-offset printing, flexographic printing, and inkjet printing. From the viewpoints of productivity and high-resolution images, gravure printing may be used.

[0035] To improve the adhesion of the printed layer 12, the surface of the PET film 11 on the side of the printed layer 12 may be subjected to various pretreatments such as corona treatment, plasma treatment, and flame treatment, or a coating layer such as an easy-adhesion layer may be provided.

[0036] [Sealant layer details] When the pressure in the storage section 20 reaches or exceeds a predetermined value, the side edge seal section 24 peels away from the inner edge at the vapor release section 28, connecting the storage section 20 to the outside of the packaging bag 2 (packaging body 1). For vapor to escape properly, the side edge seal section 24 needs to peel away appropriately in response to the pressure in the storage section 20. In other words, the structure of the sealant layer 16, which seals the side edge seal section 24, affects the ability of vapor to escape properly (vapor permeability). The structure of the sealant layer 16 that particularly affects vapor permeability is the sea-island structure present inside the sealant layer 16. The sea-island structure is a two-phase structure in which a main first phase (resin phase) exists continuously like a sea, and a second phase (rubber phase) exists discontinuously like islands within the first phase.

[0037] The sea-island structure of the sealant layer 16 can be evaluated by observing a cross section of the sealant layer 16 with a scanning probe microscope. Scanning probe microscopes include atomic force microscopes. In a scanning probe microscope, a cantilever, which acts as a measuring probe, is vibrated at a resonant frequency while scanning the sample surface to measure the surface shape. Of the images obtained, phase images are digitized by image analysis. The cross sections parallel to the machine direction (MD) of the sealant layer 16 and the cross sections parallel to the transverse direction (TD) perpendicular to the machine direction of the sealant layer 16 are evaluated.

[0038] In order to accurately observe the sea-island structure, a binarization analysis is performed on an image of a cross section of the sealant layer 16 observed with a scanning probe microscope. The binarization analysis includes, in order, contrast enhancement processing, dehazing processing, binarization processing, and shadow processing.

[0039] Contrast enhancement processing is a process that clarifies the difference between light and dark in an image. This makes bright areas brighter and dark areas darker. Contrast enhancement processing can be performed using pre-prepared software. For example, the Contrast Limited Adaptive Histogram Equalization (CLAHE) process provided in the image analysis software ImageJ (https: / / imagej.nih.gov / ij / ) can be used.

[0040] The matting process is performed on the contrast-enhanced image. The matting process sharpens the image, making it easier to identify each individual island. For example, the islands may be sharpened using machine learning using the random forest method. The matting process may be performed using pre-prepared software. For example, a plugin (Trainable Weka Segmentation: TWS) available for ImageJ may be used.

[0041] The binarization process is performed on the matte-processed image. This process converts the image into a two-tone image, for example, by using a threshold to convert pixel values ​​into two values: black and white. The binarization threshold may be determined from statistical information about the pixel values ​​contained in the image, as in Otsu's binarization method. The binarization process may be performed using pre-prepared software. For example, the binarization process provided by ImageJ can be used.

[0042] Shadow processing is performed on binarized images. Shadow processing is a process that emphasizes edges in a specific direction (for example, the horizontal direction of the image). Shadow processing can be performed using pre-prepared software. For example, the shadow processing provided by ImageJ can be used. In ImageJ's shadow processing, edges in a specific direction can be emphasized by shifting the image by 1 pixel in any direction (east, west, north, south) and taking the difference in pixels before and after the shift.

[0043] The shapes of the islands can be clearly observed in the processed images obtained by the binarization analysis. In the processed images of the cross sections of the sealant layer 16 parallel to the MD, the shapes of the islands are, on average, rectangular with the longitudinal direction extending along the MD or elliptical with the major axis extending along the MD. In the processed images of the cross sections of the sealant layer 16 parallel to the TD, the shapes of the islands are, on average, rectangular with the longitudinal direction extending along the TD or elliptical with the major axis extending along the TD. In the processed images of the cross sections parallel to the TD, the islands tend to be smaller in size and shorter in the longitudinal direction than in the processed images of the cross sections parallel to the MD.

[0044] [Section parallel to MD of sealant layer] In the processed image of the cross section parallel to the MD of the sealant layer 16, the average area of ​​the islands is 0.153 μm 2 The average area of ​​the islands is 0.144 μm 2 It may be 0.160 μm or more 2 In these cases, steam is properly passed through the steam vent 28. The average value is the average value of all the islands in the image. The average value of the island area is 0.153 μm 2 If it is less than (or 0.144 μm 2 Less than 0.160 μm 2 If the area is less than 1 / 2 mm, steam does not pass through the steam vent 28 properly. The reason for this is not clear, but it is thought that peeling of the side edge seal 24 occurs by propagating between the islands of the sea-island structure, and if the area of ​​the islands is small, there are too many propagation paths, which prevents proper peeling. In the processed images, the average area of ​​the islands is 0.763 μm 2 The average area of ​​the island portions may be 0.763 μm or less. 2 If the temperature exceeds this range, steam may not pass through the steam release portion 28 properly. This is because the sealant layer 16 softens, making it difficult to maintain the designed strength. Also, if the area of ​​the island portion is large, there is no propagation path, which is thought to prevent proper peeling.

[0045] In a processed image of a cross section parallel to the MD of the sealant layer 16, the average longitudinal length of the island portions is 1.658 μm or more. The average longitudinal length of the island portions may be 1.755 μm or more. In these cases, vapor properly passes through the vapor release portion 28. The average value is the average value of all the islands in the image. The longitudinal length of the island portions may be the longitudinal length when the island portions are approximated as a rectangle, or the length of the major axis when the island portions are approximated as an ellipse. If the average longitudinal length of the island portions is less than 1.658 μm (or less than 1.755 μm), vapor does not properly pass through the vapor release portion 28. Although the cause of this is unclear, it is believed that peeling of the side edge seal portion 24 occurs by propagating between the islands in the sea-island structure. It is presumed that if the longitudinal length of the island portions is short, their function as a propagation guide is reduced, resulting in inappropriate peeling. In the processed image, the average longitudinal length of the island portions may be 5.850 μm or less. If the average longitudinal length of the island portions exceeds 5.850 μm, steam may not properly pass through the steam release portion 28. This is because the sealant layer 16 softens, making it difficult to maintain the designed strength. Also, if the area of ​​the island portions is large, there is no propagation path, which is presumably why proper peeling does not occur.

[0046] [Section of sealant layer parallel to TD] In a processed image of a cross section of the sealant layer 16 parallel to the TD, when the islands are approximated by ellipses, the average value of the inclination of the ellipses (the angle between the major axis and the X axis) is 75.00° or more. The average value of the inclination of the ellipses may be 74.00° or more. In these cases, steam properly passes through the steam release section 28. The average value is the average value for all islands in the image. If the average value of the inclination of the ellipses is less than 75.00° (or less than 74.00°), steam does not properly pass through the steam release section 28. The cause of this is not certain, but as mentioned above, it is presumed that if the island area is small, the number of propagation paths becomes excessive, preventing proper peeling. If the island area is small, even with shadow processing, the islands will not be accurately separated, and a certain number of islands will be processed as a single group. Since the grouped islands can have various shapes overall, it is presumed that the average value of the inclination of the ellipses will be small when approximated by an ellipse. In other words, when the average value of the inclination of the ellipse is small, the individual islands are small, so there are too many propagation paths, and it is estimated that proper separation does not occur.

[0047] Although several embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments. A predetermined intermediate layer may be provided between each layer of the laminate 10 to improve the functionality of the laminate 10. The configuration of the intermediate layer can be appropriately referenced from the description of the configuration of the sealant layer 16 described above. Providing an intermediate layer in the laminate 10 can further reduce deformation of the laminate during the production of packaging bags. Multiple intermediate layers may be used depending on the application of the laminate 10.

[0048] The laminate 10 may include a vapor-deposited layer that has been previously deposited on any of the layers that make up the laminate. Vapor deposition materials used for the vapor-deposited layer include metals such as Si, Al, Sn, In, Zn, Fe, and Mn, and inorganic compounds containing one or more of these metals. Examples of such inorganic compounds include silicon oxides (SiO ), such as silicon monoxide and silicon dioxide. x), aluminum oxide, magnesium oxide, tin oxide, indium oxide, etc. In addition to these inorganic compounds, the inorganic oxide may contain at least one metal selected from the group consisting of Si, Al, Sn, In, Zn, Fe, and Mn, or an oxide thereof.

[0049] The laminate 10 may include, for example, an anchor coat layer adjacent to at least one selected from the printed layers 12. By including the anchor coat layer, the adhesion of the printed layer 12 can be increased, further improving the puncture strength of the laminate 10. The anchor coat layer can be formed by applying an anchor coat agent onto a predetermined layer and drying it. Examples of anchor coat agents include polyester-based polyurethane resins and polyether-based polyurethane resins. The thickness of the anchor coat layer is not particularly limited and may be 0.1 to 1.0 μm or 0.3 to 0.5 μm.

[0050] The PET film 11 and the nylon 6 film 14 may be bonded directly to each other without the first adhesive layer 13. Also, the nylon 6 film 14 and the sealant layer 16 may be bonded directly to each other without the second adhesive layer 15. [Example]

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

[0052] [Packaging preparation] A commercially available polyethylene terephthalate (PET) film with a thickness of 12 μm, a commercially available nylon 6 film with a thickness of 15 μm, and a commercially available unoriented polypropylene (CPP) film with a thickness of 60 μm were prepared. The CPP film functions as a sealant layer. CPP film A, CPP film B, and CPP film C, each with a different sea-island structure, were prepared.

[0053] A laminate was prepared by bonding a PET film, a nylon 6 film, and a CPP film A with an aliphatic ester adhesive. Two square laminates measuring 130 mm x 130 mm were cut from the prepared laminate, with two sides parallel to the MD of the CPP film A. The two cut-out laminates were overlapped with the CPP film A facing inward while aligning the MD of the CPP film A. One of the four sides of the square perpendicular to the MD of the CPP film A was heat-sealed to form a steam release hole. Two heat-sealing conditions were set. The first heat-sealing condition was a pressure of 0.2 MPa, a treatment time of 1.5 seconds, and a treatment temperature of 190 to 220°C. The second heat-sealing condition was a pressure of 0.1 to 0.3 MPa, a treatment time of 1.5 seconds, and a treatment temperature of 200°C.

[0054] Next, two of the remaining three sides of the square were heat-sealed, and 50 ml of water was filled into the remaining side and heat-sealed to form a filled product. The filled product was then subjected to a spray retort treatment. The conditions for the spray retort treatment were a treatment temperature of 121°C and a treatment time of 30 minutes. The filled product that had undergone the spray retort treatment was allowed to cool for 12 hours or more to form a package. As a result, six packaged products were prepared as samples: a packaged product made with CPP film A under the first heat-sealing conditions, a packaged product made with CPP film A under the second heat-sealing conditions, a packaged product made with CPP film B under the first heat-sealing conditions, a packaged product made with CPP film B under the second heat-sealing conditions, a packaged product made with CPP film C under the first heat-sealing conditions, and a packaged product made with CPP film C under the second heat-sealing conditions.

[0055] [Observation of sea-island structure] A cross section of the sealant layer 16 in the unsealed portion of the sample was prepared to observe the sea-island structure. The cross section of the sealant layer 16 was prepared as follows: First, the front and back surfaces of the sample were corona-treated, and then the sample was cut into 2 mm x 3 mm strips. The resulting strips were then embedded in a photocurable resin (visible light-curable resin, Aronix LCR D-800, manufactured by Toa Gosei Co., Ltd.), and the resin was cured by light irradiation to obtain a block consisting of the sample and the cured resin in which it was embedded. The resulting block was then fixed in an insert for an SPM sample holder (an insert for an AFM sample holder manufactured by Leica Microsystems). At room temperature (25°C), the block was trimmed with a glass knife, and the sample cross section (perpendicular to the layer interface and parallel to the MD or TD) was cut with a diamond knife until the cross section was mirror-finished under cooling at -40°C. The cross-section cutting device used was a Leica Microsystems ultramicrotome EMUC7 in combination with a cooling option EM FC7. The cutting speed was set to 1 mm / s, and the cutting film thickness was set to 200 nm. The cutting direction was parallel to the MD or TD of the sealant layer 16.

[0056] The cross section of the sealant layer 16 is observed using the following method. After cutting the cross section, the block piece is fixed in place using an SPM sample holder insert. A phase image is measured using an SPM (scanning probe microscope) at the center of the sample thickness of the block piece. The measurement conditions for the cross section parallel to the MD of the sealant layer 16 are as follows: the MD of the sample is the X direction, the thickness direction of the sample is the Y direction, the field of view is 20 μm in the X direction, 10 μm in the Y direction, and the resolution is 1024 in the X direction and 512 in the Y direction. The measurement conditions for the cross section parallel to the TD of the sealant layer 16 are as follows: the TD of the sample is the X direction, the thickness direction of the sample is the Y direction, the field of view is 10 μm in both the X and Y directions, and the resolution is 512. Furthermore, the shape is measured using the SPM's AC mode (tapping mode) at a scanning speed of 0.5 Hz, with the X direction as the fast scan scanning direction. Phase, height, and amplitude images are obtained. The SPM used is a JupiterXR (trade name) manufactured by Oxford Instruments. The SPM cantilever (measurement probe) is an AC160TS (trade name) manufactured by Olympus, with typical characteristics of a tip curvature radius of 7 nm and a spring constant of 26 N / m. The Setpoint, Drive Amplitude, and Integral Gain are adjusted so that the sea-island structure can be clearly observed in the phase image. Specifically, the phase during measurement in the phase image is adjusted to be smaller than the phase before the cantilever and sample engage, the trace and retrace signals are aligned in the height image, and the trace and retrace signals are inverted in the amplitude image.

[0057] The above-mentioned measurements were performed for each sample at one or two locations on a cross section parallel to the MD of the sealant layer 16, and at five locations on a cross section parallel to the TD of the sealant layer 16. Since the phase value may gradually fluctuate due to changes in the state of the cantilever tip during measurement, the influence of fluctuations was reduced by performing a plane fit process on the phase image after measurement using JupiterXR analysis software. The obtained phase image was quantified using JupiterXR analysis software.

[0058] The phase image digitized by Jupiter XR was opened in Image J and subjected to binarization analysis to obtain a processed image. Figure 5(A) is an example of an image opened in Image J. The binarization analysis was performed using functions provided in Image J. Specifically, contrast enhancement processing was performed using CLAHE, and matting processing was performed using TWS, followed by binarization and shadow processing to obtain a processed image. Figure 5(B) is an example of an image subjected to contrast enhancement processing. Figure 5(C) is an example of an image subjected to matting processing. Figure 5(D) is an example of an image subjected to binarization processing. Figure 5(E) is an example of an image subjected to shadow processing. The image shown in Figure 5(E) is an example of a processed image.

[0059] For processed images of cross sections parallel to the MD of the sealant layer 16, the area and longitudinal length of the islands in the processed images were measured, and the average value of all the islands was calculated. The area and length measurements were performed in pixels. The results are shown in Table 1 and Figure 6(A). Figure 6(A) is a graph plotting the average island area for each sample. The area is in pixels. Figure 6(B) is a graph plotting the average island length (approximated as a rectangle) for each sample. The length is in pixels. Figure 6(C) is a graph plotting the average island length (approximated as an ellipse) for each sample. The length is in pixels. Table 1 also shows values ​​converted to SI units, assuming 1px = 0.0195 μm. [Table 1] Here, the average area of ​​the islands is 400.0 px or more (0.153 μm 2 The sample with a particle size of less than 400.0 px (0.153 μm or more) is used as an example. 2The samples in which the average longitudinal length of the island portions in the examples was 85.00 px or more (1.658 μm or more), and the average longitudinal length of the island portions in the comparative examples was less than 85.00 px (less than 1.658 μm), may be distinguished from the comparative examples only by the measurement results of the average longitudinal length of the island portions.

[0060] For the above-described Examples and Comparative Examples, processed images of cross sections parallel to the TD of the sealant layer 16 were observed, and the inclination of the ellipse (the angle between the major axis and the X axis) when the island portions shown in the processed images were approximated by an ellipse was measured, and the average value for all island portions was calculated. The results are shown in Table 2 and Figure 7. Figure 7 is a graph in which the average value of the inclination of the ellipse is plotted for each sample. [Table 2] Here, for Example A, five measurement locations were used, and they were designated Examples A-1 to A-5. For Example B, five measurement locations were used, and they were designated Examples B-1 to B-5. For Comparative Example C, five measurement locations were used, and they were designated Comparative Examples C-1 to C-5. Since the average value of the inclination of the ellipses in the Examples is 75.00° or more, and the average value of the inclination of the ellipses in the island portions in the Comparative Examples is less than 75.00°, the Examples and Comparative Examples may be distinguished only by the measurement results of the average value of the inclination of the ellipses in the island portions.

[0061] [Confirmation of vapor permeability] The samples according to the examples and comparative examples were cooked in a microwave oven to check their steam permeability. Specifically, they were cooked at 600 W for two minutes to check whether they could be steamed. The results are shown in Table 3. [Table 3] The samples prepared under the first heat sealing condition are Examples A, B, and C, and the samples prepared under the second heat sealing condition are Examples A1, B1, and C1. Thus, in the processed image of the cross section parallel to the MD of the sealant layer 16, the average area of ​​the island portions is 0.153 μm 2 In the above-mentioned Examples A, A1, B, and B1, steam permeation was confirmed, and the thickness was 0.153 μm. 2 In processed images of cross sections parallel to the MD of the sealant layer 16, vapor passage was confirmed in Examples A, A1, B, and B1 in which the average longitudinal length of the island portions was 1.658 μm or more, but not in Comparative Examples C and C1 in which the average longitudinal length was less than 1.658 μm. Furthermore, in processed images of cross sections parallel to the TD of the sealant layer 16, vapor passage was confirmed in Examples A, A1, B, and B1 in which the average inclination of the ellipse obtained by approximating the island portions with an ellipse was 75.00° or more, but not in Comparative Examples C and C1 in which the average inclination was less than 75.00°. Thus, it was demonstrated that a package having vapor permeability can be defined using new parameters related to the sea-island structure. [Explanation of symbols]

[0062] 1...packaging body, 10, 10a, 10b, 10c...laminate body, 11...polyethylene terephthalate film, 16...sealant layer.

Claims

1. A package for microwave cooking made of a laminate including a polyethylene terephthalate film and a sealant layer, The sealant layer has an internal sea-island structure, and in a processed image obtained by observing a cross section of the sealant layer parallel to the machine direction with a scanning probe microscope and subjecting the image to contrast enhancement processing, de-hazing processing, binarization processing, and shadow processing, the average area of ​​the island portions is 0.153 μm ２ That's it, the package.

2. A package for microwave cooking made of a laminate including a polyethylene terephthalate film and a sealant layer, The package has an internal sealant layer having an island-sea structure, and in a processed image obtained by observing a cross section of the sealant layer parallel to the machine direction with a scanning probe microscope, the image is subjected to contrast enhancement processing, matting processing, binarization processing, and shadow processing, and the average longitudinal length of the island portions is 1.658 μm or more.

3. A laminate constituting the packaging body according to claim 1 or 2.

Images