Packaging body

Abstract

Provided is a packaging body that can be used as a container after a heating treatment.　A packaging body 1 that can be subjected to a heating treatment comprises an expandable internal space 4 surrounded by a surface layer 2 and a back layer 3. The surface layer 2 and / or the back layer 3 contains paper and / or pulp, and the packaging body 1 can be used as a container after the heating treatment. The surface layer 2 and the back layer 3 are configured to be at least partially separable after the heating treatment, and a pressure-reducing port is provided to suppress an excessive increase in pressure in the internal space 4. Creases 80 are preferably provided for establishing folding lines in the surface layer 2 and / or the back layer 3 when the internal space 4 is expanded.

Description

packaging

[0001] The present invention relates to a heat treatable package.

[0002] For example, a flat-type pouch is known in which a packaging bag filled with contents such as food is laid flat in a microwave oven for heating (see, for example, Patent Document 1).

[0003] Patent Document 1 discloses a plastic pouch formed by overlapping a plastic film constituting the front surface of the pouch with a plastic film constituting the back surface of the pouch and heat-sealing the periphery. In this plastic pouch, an opening is provided at a position away from the heat-sealed periphery, and a steam release seal is formed to surround the opening.

[0004] When this plastic pouch is placed flat in a microwave oven and heated, the internal pressure of the pouch increases due to steam generated by the contents, causing the pouch to expand. As the pouch expands, the steam release seal gradually peels away toward the opening. When the peeling continues until it reaches the opening, the steam and other substances are released through the opening to the outside, reducing the internal pressure of the pouch.

[0005] Japanese Patent Application Laid-Open No. 2006-62672

[0006] In the plastic pouch described in Patent Document 1, both the front and back surfaces of the pouch are made of plastic film, so even if both the front and back surfaces of the pouch are deformed into an expanded shape as the internal pressure of the pouch increases, the expanded shape is not maintained after heating is completed, and the pouch contracts due to a decrease in internal pressure of the pouch. For this reason, with the plastic pouch described in Patent Document 1, it is necessary to transfer the contents to another container after cooking in a microwave oven, which is inconvenient.

[0007] The present invention has been made in view of the above problems, and has an object to provide a package that can be used as a container after heat treatment.

[0008] The characteristic configuration of the packaging body of the present invention for solving the above problem is that it is a packaging body that can be heated and has an expandable internal space surrounded by a surface layer and a back layer, and at least one of the surface layer and the back layer contains paper and / or pulp, and is configured so that it can be used as a container after heat treatment.

[0009] In the package of this configuration, when the pressure in the internal space surrounded by the front and back layers increases due to heat treatment, the internal space expands, and the front and back layers are deformed into a bulging shape. According to the package of this configuration, because at least one of the front and back layers contains paper and / or pulp, once at least one of the front and back layers is deformed into a bulging shape, the shape retention (plasticity) of the paper and / or pulp allows the deformed shape to be maintained. Thus, at least one of the front and back layers is maintained in a form capable of containing and retaining the contents, making it usable as a container.

[0010] In the packaging body according to the present invention, it is preferable that the outer layer and the inner layer are at least partially separable after heat treatment.

[0011] According to the package of this configuration, the outer layer and the inner layer are at least partially separated after the heat treatment, and the contents can be easily removed through the opening formed by the separation.

[0012] The packaging body according to the present invention preferably includes a pressure reducing port that prevents an excessive increase in pressure in the internal space.

[0013] With this type of package, the pressure in the internal space can be released through the pressure reduction port before it becomes too high. As a result, the package can be prevented from bursting or the contents from spilling out of the package. Packages with such pressure reduction ports are suitable for use in microwave cooking.

[0014] In the packaging body according to the present invention, it is preferable that a crease be provided in at least one of the front layer and the back layer when the internal space is expanded.

[0015] When the internal space of the package expands, the area around the lines on at least one of the front and back layers is folded and raised along the lines. Therefore, by providing lines at the desired folding locations on at least one of the front and back layers, the package can be easily deformed into the intended shape. Furthermore, providing lines can prevent the package from curling toward the front or back layer.

[0016] In the packaging body according to the present invention, it is preferable that the lines include a first line extending in a direction toward the center of the front layer and / or the back layer, and a second line extending so as to surround the center of the front layer and / or the back layer.

[0017] With this package, when the internal space expands, the peripheral portions of the first scores extending in a direction toward the center of the front and / or back layers (the center of the surface of the front and / or back layers as viewed from the direction in which the front and back layers are superimposed) are raised in a folded state along the first scores, and the peripheral portions of the second scores extending so as to surround the center of the front and / or back layers are raised in a folded state along the second scores, thereby enabling the package to be reliably deformed into the intended container shape.

[0018] In the package according to the present invention, it is preferable that the first score line and the second score line are not parallel to each other and do not intersect each other.

[0019] If the first and second creases intersect, stress may be concentrated at a specific portion where the first and second creases intersect when the first and second creases act as creases and the peripheral portions of the creases bend during expansion of the internal space of the package. Furthermore, if the first and second creases are parallel to each other, stress may be concentrated at a specific portion between the first and second creases when the peripheral portions of the creases bend during expansion of the internal space of the package. Stress concentration at a specific portion may affect the shape and durability of the container after deformation of the package. Therefore, by adopting a configuration in which the first and second creases are arranged not parallel to each other and not intersect, as in the present configuration, stress concentration between the creases during expansion of the internal space can be prevented.

[0020] In the packaging body according to the present invention, it is preferable that the creases include convex creases that protrude toward the front layer side and concave creases that are recessed toward the back layer side.

[0021] By providing a package with convex creases that protrude from the surface layer side, when the internal space of the package expands, the package can be folded using the convex creases as folds so that the areas around the creases protrude toward the inside of the container when the package is shaped like a container. Also, by providing concave creases that are recessed from the back layer side, the package can be folded using the concave creases as folds so that the areas around the creases protrude toward the outside of the container when the package is shaped like a container when the internal space of the package expands. According to this configuration of the package, the creases include convex creases and concave creases, and by providing an appropriate combination of convex creases and concave creases, the areas around the creases can be protruded in a balanced manner inside and outside the container, allowing the package to be deformed into a stable container shape.

[0022] In the packaging body according to the present invention, the ruled lines are preferably provided to match the shape of the container when used as the container.

[0023] With this configuration of packaging, when the internal space expands, the packaging is raised in a folded state along the lines that are provided to match the shape of the container when it is used as a container, so that the packaging can be reliably deformed to match the shape of the container when it is used.

[0024] In the packaging body according to the present invention, it is preferable that the ruled lines are provided in accordance with the contents to be contained in the container.

[0025] With this configuration of packaging, when the internal space expands, the lines provided to fit the contents contained in the container act as creases and the packaging is raised in a folded state, allowing the packaging to be reliably deformed to the shape of the container to fit the contents.

[0026] In the packaging body according to the present invention, it is preferable that the packaging body be configured so as to satisfy h ≧ 0.4T, where T is the total thickness of the front layer and the back layer, and h is the amount by which the ruled lines protrude from the front layer or the back layer.

[0027] With this configuration of packaging, by designing the amount of protrusion h of the line from the front or back layer to be 0.4 times or more the total thickness T of the front and back layers, when the internal space expands, the area around the line can be reliably folded and raised using the line as a crease.

[0028] In the packaging body according to the present invention, it is preferable that the amount of protrusion of the ruled lines from the front layer or the back layer is 80 μm or more.

[0029] According to the packaging body of this configuration, by designing the lines to protrude from the front or back layer by 80 μm or more, when the internal space expands, the area around the lines can be reliably folded and raised using the lines as creases.

[0030] In the packaging body according to the present invention, it is preferable that in the area where the front layer and the back layer overlap in a plan view, a seal portion is provided that is joined in a convex shape toward the inward side of the area so as to overlap the line.

[0031] With this type of packaging, when the pressure in the internal space increases and the internal space expands, stress is concentrated in the area where the front and back layers overlap in a planar view, at the seal portion that is joined in a convex shape toward the inside of the area so as to overlap the line.As a result, when the internal space expands, the area around the line is raised in a state where it is bent more deeply using the line as a fold, and the container can be formed into a deeper, intended shape.

[0032] In the packaging body of the present invention, it is preferable that in the area where the front layer and the back layer overlap in a planar view, a seal portion is provided that has a portion that is joined so as to follow the edge of the area and a portion that is joined so as not to follow the edge of the area.

[0033] According to the packaging body of this configuration, by providing the above-mentioned seal portion, it is possible to shorten the distance from the center of the area where the front layer and the back layer overlap in a plan view to the joining portion so as not to follow the edge of the area. Here, when the internal space surrounded by the front layer and the back layer expands, the shorter the distance from the center of the area where the front layer and the back layer overlap in a plan view, the easier it is for the joining portion to rise so as not to follow the edge of the area.

[0034] In the packaging body according to the present invention, the surface layer and / or the back layer is preferably a multi-layer sheet having a sealant layer containing a resin and a paper layer containing the paper and / or the pulp.

[0035] According to the packaging body of this configuration, the sealant layer ensures heat sealing properties and the like, and the paper layer ensures shape retention (plasticity) of the packaging body after deformation.

[0036] In the packaging body according to the present invention, it is preferable that the outer layer and the inner layer are configured to have different rigidities.

[0037] According to the packaging body of this configuration, the layer with relatively low rigidity between the front and back layers can be deformed more significantly than the layer with relatively high rigidity, so that the packaging body after deformation can be used as a container.

[0038] In the packaging body according to the present invention, it is preferable that the packaging body can maintain the shape that functions as a container for 5 minutes or more after heat treatment.

[0039] With the packaging of this configuration, if the form that functions as a container is maintained for 5 minutes or more, for example, if the contents are food, the packaging can be used as a container as is while the food is being eaten.

[0040] In the packaging body according to the present invention, it is preferable that the front layer and / or the back layer is a multilayer sheet having at least a paper layer containing the paper and / or the pulp, and that the multilayer sheet is formed into a loop-shaped sample piece having a circumference of 100 mm, and the loop stiffness measured when the sample piece is pressed with a pressing length of 10 mm is 40 mN / 15 mm width or more.

[0041] With this type of packaging, the loop stiffness measured under the above test conditions is set to 40 mN / 15 mm width or more, so that the stiffness of the multilayer sheet is not too low, and a certain level of rigidity can be ensured after it has been deformed into the shape of a container, thereby ensuring sufficient functionality and durability as a container.

[0042] In the packaging body according to the present invention, it is preferable that the ratio (LS1 / LS2) of the loop stiffness (LS1) in the MD direction of the paper layer to the loop stiffness (LS2) in the TD direction of the paper layer is 1.0 to 1.5.

[0043] In the packaging of this configuration, the ratio (LS1 / LS2) of the loop stiffness (LS1) in the MD direction (the direction of papermaking flow) of the paper layer to the loop stiffness (LS2) in the TD direction (the direction perpendicular to the direction of papermaking flow) of the paper layer is set to 1.0 to 1.5. Within this range, the balance of stiffness in the MD and TD directions of the multilayer sheet is appropriate, preventing uneven deformation in either the MD or TD direction and ensuring reliable deformation to the container shape. Furthermore, after deformation, the shape retention (plasticity) of the paper layer allows the packaging to maintain a stable container shape.

[0044] The packaging body according to the present invention is preferably used as a food container for heating, for enclosing food to be cooked in a microwave oven.

[0045] With this type of packaging, the internal space can be expanded by steam generated from the food when cooked in a microwave oven, allowing at least one of the outer and inner layers to be used as a container capable of holding and storing food.

[0046] FIG. 1 is a perspective view showing a package according to one embodiment of the present invention. FIG. 2 is an explanatory diagram of the structure of the package. FIG. 3 is an explanatory diagram of the laminated structure of the top sheet and the back sheet. FIG. 4 is an explanatory diagram of the heat-sealed portion and the score lines. FIG. 5 is an explanatory diagram of the procedure for use as a food container for heating. FIG. 6 is a perspective view showing the back sheet used as a container. FIG. 7 is an explanatory diagram of another embodiment of the heat-sealed portion. FIG. 8 is an explanatory diagram of another embodiment of the score lines. FIG. 9 is an explanatory diagram of a seal portion attached to the peripheral seal portion. FIG. 10 is an explanatory diagram of an example (1) of the arrangement of different types of score lines. FIG. 11 is an explanatory diagram of an example (2) of the arrangement of different types of score lines. FIG. 12 is an explanatory diagram of an example (3) of the arrangement of different types of score lines. FIG. 13 is an explanatory diagram of an example (4) of the arrangement of different types of score lines. FIG. 14 is an explanatory diagram of an example (5) of the arrangement of different types of score lines. FIG. 15 is an explanatory diagram of an example (6) of the arrangement of different types of score lines. FIG. 16 is an explanatory diagram of the height and width of score lines. FIG. 17 is an explanatory diagram of a method for measuring loop stiffness.

[0047] The present invention will be described below with reference to the drawings. In the following embodiments, a package used as a food container for heating food (contents M) to be cooked in a microwave oven will be described as an example. However, the present invention is not intended to be limited to the embodiments described below, the configurations shown in the drawings, or the examples. In Figures 1 to 3, 5, 6, and 16, the thicknesses of the front layer 2 and the back layer 3, and the thickness relationships among the multiple layers 41, 42, 51 to 54 that make up each layer 2 and 3, are appropriately exaggerated or simplified, and do not strictly reflect the actual thickness relationships (scale) of each layer.

[0048] <Schematic Configuration> Fig. 1 is a perspective view showing a package 1 according to one embodiment of the present invention. Fig. 1(a) is a perspective view showing the package 1 containing a content M before expansion, and Fig. 1(b) is a perspective view showing the package 1 containing the content M after expansion. The package 1 shown in Figs. 1(a) and 1(b) comprises a surface layer 2 and a back layer 3, and has an expandable internal space 4 surrounded by the surface layer 2 and the back layer 3. At least one of the surface layer 2 and the back layer 3 contains paper and / or pulp, which are a type of molding sheet and / or molding filler, and is configured to be usable as a container after heat treatment. Below, an example in which the back layer 3 contains paper and / or pulp will be described. In this embodiment, both the surface layer 2 and the back layer 3 are made of sheet material. Hereinafter, the "surface layer 2" will be referred to as the "surface sheet 2," and the "back layer 3" will be referred to as the "back sheet 3."

[0049] Figure 2 is an explanatory diagram of the structure of the package 1. Figure 2(a) is an exploded perspective view of the package 1 before heat sealing. Figure 2(b) is a perspective view of the package 1 in which the front sheet 2 and the back sheet 3 are heat-sealed. In practice, the package 1 shown in Figure 2(b) is produced by subjecting a laminated material sheet in which the material sheet of the front sheet 2 and the material sheet of the back sheet 3 are overlapped and heat-sealed to a punching process for punching out the outline and a process for carving ruled lines 80, which will be described later.

[0050] 2(a), the top sheet 2 has a rectangular (square) outline in plan view, and has a first set of opposite sides (sides 11 and 12) that are a set of two parallel, opposing sides, and a second set of opposite sides (sides 13 and 14) that are perpendicular to the first set of opposite sides 11 and 12. The back sheet 3 has a rectangular (square) outline in plan view, like the top sheet 2, and has approximately the same area, a first set of opposite sides (sides 21 and 22) that are a set of two parallel, opposing sides, and a second set of opposite sides (sides 23 and 24) that are perpendicular to the first set of opposite sides 21 and 22 and are parallel to each other.

[0051] In Figure 2(b), the top sheet 2 and the back sheet 3 are overlapped so that the first pair of opposite sides 11, 12; 21, 22 and the second pair of opposite sides 13, 14; 23, 24 are aligned in a plan view, and the necessary portions are heat-sealed except for a predetermined area between both ends of the opposite sides 12, 22 that will become the filling port 5 for the contents M. The heat-sealed portions are indicated in Figure 2(b) by the symbol "HS."

[0052] 2(b), after filling the internal space 4 between the top sheet 2 and the back sheet 3 with the contents M (see FIG. 1(a)), a predetermined area between both ends of the opposite sides 12, 22 is heat-sealed to close the filling opening 5, thereby producing the package 1 in a sealed state containing the contents M, as shown in FIG. 1(a). As the contents M are enclosed, ridge lines R appear on the top sheet 2 of the package 1 from the center of the sheet toward the four corners. In this package 1, the first set of opposite sides (sides 31 and 32) includes the first set of opposite sides 11, 12 on the top sheet 2 and the first set of opposite sides 21, 22 on the back sheet 3. In addition, in this package 1, the second set of opposite sides (sides 33 and 34) includes the second set of opposite sides 13, 14 on the top sheet 2 and the second set of opposite sides 23, 24 on the back sheet 3.

[0053] <Top Sheet> Figure 3 is an explanatory diagram of the laminated structure of the top sheet 2 and the back sheet 3. Figure 3(a) is a cross-sectional view showing the laminated structure of the top sheet 2. The top sheet 2 is a multi-layer sheet in which a base layer 41 and a sealant layer 42 are laminated. The base layer 41 is disposed on the outer side of the package 1. The sealant layer 42 is disposed so as to face the internal space 4 of the package 1.

[0054] The base layer 41 constituting the top sheet 2 is not particularly limited as long as it is made of a heat-resistant resin film that can be used as food packaging material generally used in microwave cooking. Examples of resins include polyethylene terephthalate (PET), nylon film (Ny), polypropylene (PP), polyvinylidene chloride (PVDC), polyvinyl chloride (PVC), polymethylpentene (PMP), and polyethylene (PE). The resin film may be stretched. Alternatively, the resin film may be a composite resin film formed by laminating two or more of these resins. The thickness of the base layer 41 is preferably 10 to 200 μm, and more preferably 20 to 150 μm.

[0055] The sealant layer 42 constituting the top sheet 2 is not particularly limited as long as it is a thermo-adhesive resin film that does not affect the contents and is generally suitable for use as packaging for food heated or cooked in a microwave oven. Examples of resin types include ethylene-based resins such as low-density polyethylene resin (LDPE), medium-density polyethylene resin (MDPE), linear low-density polyethylene resin (LLDPE), ethylene-vinyl acetate copolymer (EVA), ethylene-α-olefin copolymer, and ethylene-methacrylic acid copolymer; blends of polyethylene and polybutene; homopolypropylene resin (PP), propylene-ethylene random copolymer, propylene-ethylene block copolymer, and propylene-α-olefin copolymer; and polypropylene-based resins such as these. The resin film may also be a composite resin film formed by laminating two or more of these resins. The top sheet 2 may also include a paper layer containing paper and / or pulp, as described below. The thickness of the sealant layer 42 is preferably 20 to 80 μm, more preferably 30 to 50 μm.

[0056] <Backing sheet> Figure 3(b) is a cross-sectional view showing the layered structure of the backing sheet 3. The backing sheet 3 has a sealant layer 51, a base layer 52, a paper layer 53 and an overprint varnish layer (hereinafter referred to as "OP varnish layer") 54, and when the paper layer 53 is used as a reference, the base layer 52 and the sealant layer 51 are laminated in this order on one side of the paper layer 53 toward the internal space 4 of the package 1, and the OP varnish layer 54 is laminated on the other side of the paper layer 53 toward the outside of the package 1.

[0057] Like the sealant layer 42 of the front sheet 2, the sealant layer 51 of the back sheet 3 is required to have heat-sealing properties and not affect the contents, and also function as an easy-peel layer. The sealant layer 51 can be composed of, for example, the following different types of resins A and B. Specifically, resin A can be at least one selected from the group consisting of linear low-density polyethylene (LLDPE), 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-methyl acrylate copolymer (EMA), and ionomers thereof. Ethylene-vinyl acetate copolymer (EVA) is particularly preferred for resin A. Polypropylene (PP) or polybutylene (PB) can be used for resin B. Polypropylene (PP) can be any of a random copolymer, homopolymer, block copolymer, etc., with random copolymers being particularly preferred. The thickness of the sealant layer 51 is preferably 20 to 80 μm, and more preferably 30 to 50 μm.

[0058] The substrate layer 52 of the back sheet 3 can be made of the same resin film as the substrate layer 41 of the front sheet 2. However, the types of resin used may be different between the substrate layer 52 of the back sheet 3 and the substrate layer 41 of the front sheet 2. The thickness of the substrate layer 52 is preferably 5 to 50 μm, and more preferably 10 to 30 μm.

[0059] <Paper Layer> The paper layer 53 is a structural layer containing paper and / or pulp. The paper layer 53 may be any paper containing 50% or more pulp fibers (cellulose fibers), and may be a mixed paper containing resin fibers in addition to pulp fibers. The type of paper constituting the paper layer 53 is not particularly limited. Examples of paper types include one-side gloss kraft paper, two-side gloss kraft paper, waterproof paper, greaseproof paper, and cup base paper. Of these, one-side gloss kraft paper and two-side gloss kraft paper are preferred in terms of strength, bending resistance, and printability. The basis weight of the paper used for the paper layer 53 is 30 to 400 g / m ２ and 50 to 300 g / m ２ It is preferable that the density is 50 to 120 g / m ２ In this example, the basis weight of the paper is 120 g / m ２ The thickness of the paper layer 53 is preferably 20 to 800 μm, and more preferably 40 to 600 μm.

[0060] The OP varnish layer 54 functions as a coating layer that covers the paper layer 53, and contains a water-resistant resin. Examples of water-resistant resins include polyolefin resins such as polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, and vinyl chloride-vinyl acetate copolymers, silicone resins, acrylic resins, epoxy resins, polyester resins, cellulose resins, and urethane resins.

[0061] As described above, the backing sheet 3 is a multilayer sheet formed by laminating the sealant layer 51, the base layer 52, the paper layer 53, and the OP varnish layer 54, and has at least the sealant layer 51 and the paper layer 53. Therefore, the sealant layer 51 can ensure heat sealing properties, and the paper layer 53 can ensure shape retention (plasticity) of the backing sheet 3 after deformation.

[0062] The method for producing a laminate by laminating the substrate layer 41 and sealant layer 42 that constitute the front sheet 2, and the sealant layer 51, substrate layer 52, paper layer 53, and OP varnish layer 54 that constitute the back sheet 3, is not particularly limited. The laminate can be produced by laminating multiple layers simultaneously or sequentially. For example, a film comprising each layer can be produced at once by co-extrusion using an extruder equipped with a die using an existing method such as the T-die method or tubular method. Alternatively, the resin, paper, etc. that constitute each layer can be separately formed into sheets, and then laminated using a wet lamination method, hot melt lamination method, dry lamination method, press method, extrusion lamination method, etc. to produce a laminate sequentially.

[0063] The front sheet 2 and the back sheet 3 are configured to have different rigidities (elastic moduli) depending on the type and thickness of the constituent materials of each layer that makes up the front sheet 2 and the back sheet 3. In this example, the back sheet 3 including the paper layer 53 is configured to have higher rigidity than the front sheet 2, so that the front sheet 2, which has a relatively low rigidity compared to the back sheet 3, can be significantly deformed and the deformed back sheet 3 can be used as a container.

[0064] 4A and 4B are explanatory diagrams of the heat-sealed portion 60 and the ruled lines 80. Fig. 4A is a plan view showing the heat-sealed portion 60 appearing on the surface side of the package 1. The package 1 has the heat-sealed portion 60, where the front sheet 2 and the back sheet 3 are joined by thermal fusion through heat sealing.

[0065] 4(a), the heat-sealed portion 60 includes peripheral sealed portions 61-65 and non-peripheral sealed portions 71-74. The peripheral sealed portions 61-65 are provided so as to extend along the edges of the sides 31-34 of the package 1 in a region shorter than the length of each of the sides 31-34, with a slight gap between them. The non-peripheral sealed portions 71-74 are provided so as to connect the ends of adjacent peripheral sealed portions 61, 63; 61, 64; 62, 63; 62, 65 at positions away from the four corners (the intersections of the sides 31-34) of the package 1, but not along the edges of the corners. In this example, the non-peripheral seal portions 71 to 74 are formed in an arc shape that bulges toward the four corners of the packaging body 1, in other words, in an arc shape that bulges in a direction away from the intersection of the diagonals of the packaging body 1 (the center O of the packaging body 1).

[0066] The heat-sealed portion 60 further includes a steam-permeable seal portion 66 provided between the peripheral seal portions 64 and 65. The steam-permeable seal portion 66 is formed in a V-shaped protrusion from the side 34 along which the peripheral seal portions 64, 65 are provided toward the intersection of the diagonals of the package 1 (the center O of the package 1). An unsealed portion 6 where the front sheet 2 and the back sheet 3 are not heat-sealed is formed between the steam-permeable seal portion 66 and the side 34.

[0067] In the package 1, the top sheet 2 and the back sheet 3 have the same shape and area, and therefore the top sheet 2 (top layer) and the back sheet 3 (back layer) overlap over the entire area in a plan view of the package 1. In the area where the top sheet 2 and the back sheet 3 overlap in a plan view, that is, over the entire area in a plan view of the package 1, a heat-sealed portion 60 is provided. The heat-sealed portion 60 has portions that are joined along the edges of the area (peripheral seal portions 61-65) and portions that are joined not along the edges of the area (non-peripheral seal portions 71-74).

[0068] <Creasing Lines> Figure 4(b) is a bottom view showing creases 80 that appear on the back layer side of the package 1. The package 1 has creases (folding lines) 80 that radiate from the intersection of the diagonals of the package 1 (the center O of the package 1) and are located on the perpendicular bisectors of each of the sides 31 to 34. In other words, the package 1 has creases 80 that extend from the midpoint of each of the sides 31 to 34 toward the center of the package 1 (the center of the surface of the package 1 in a plan view). In this embodiment, the creases 80 extend between each of the sides 31 to 34 and an imaginary circle VC that is centered at the center O of the package 1 and has a diameter of 0.2 to 0.7L (0.5L in this example). In this example, convex creases (80, 101, 102, 104, 110) and concave creases (103, 105-109) as described below are used to facilitate folding of the desired portion of the package 1, but the present invention is not limited to these. Perforated cut lines formed by a razor blade or laser processing may also be used as a means for facilitating folding. Incidentally, providing crease 80 can prevent the package 1 from curling toward the front layer side (the front sheet 2 side) or the back layer side (the back sheet 3 side).

[0069] 2(a), the scores 80 have linear protrusions 80a formed on one surface of the back sheet 3 facing the interior space 4, and linear recesses 80b formed on the other surface of the back sheet 3 so as to be inseparable from the linear protrusions 80a (the same applies to scores 101, 102, 104, and 110 described below). By providing such scores 80, when the interior space 4 of the package 1 expands, the portions of the back sheet 3 surrounding the scores 80 are raised, and at the same time, the portions surrounding the scores 80 are bent so that the linear protrusions 80a become the peaks of the folds and the linear recesses 80b become the valleys of the folds, and the portions surrounding the scores 80 are raised in a bent state with the scores 80 as folds.

[0070] Figure 5 is an explanatory diagram of the procedure for use as a food container for heating. When the package 1 configured as described above is used as a food container for heating to enclose food (contents M) to be cooked in a microwave oven MO, as shown in Figure 5(a), the package 1 containing the contents M is placed flat in the microwave oven MO, and after setting the desired heating conditions (wattage, heating time, etc.), the cooking start button (not shown) is pressed to heat the food. Then, steam and other factors generated from the contents M increase the internal pressure of the internal space 4 surrounded by the top sheet 2 and the back sheet 3, causing the internal space 4 of the package 1 to expand, as shown in Figure 5(b). As the internal space 4 expands, both the top sheet 2 and the back sheet 3 are deformed into a puffed shape. In the package 1, the distance from the center (center O of the package 1 (see FIG. 4(a)) of the area where the top sheet 2 and the back sheet 3 overlap in a plan view (the entire area of ​​the package 1 in a plan view) to the area where the sheets are joined so as not to follow the edges of that area, i.e., the non-peripheral seal portions 71 to 74, can be shortened, so that the non-peripheral seal portions 71 to 74 can easily rise when the internal space 4 expands. Therefore, the non-peripheral seal portions 71 to 74 can easily rise. Furthermore, when the internal space 4 expands, the area around the line 80 (see FIG. 4(b)) on the back sheet 3 rises in a folded state, with the line 80 as a fold.

[0071] As the internal pressure of the internal space 4 increases, stress concentrates at the tip of the vapor-permeable seal portion 66 (see FIG. 4( a) ) that protrudes toward the center O of the package 1. This causes the vapor-permeable seal portion 66 to gradually peel away toward the unsealed portion 6 (see FIG. 4( a) ). When the peeling progresses until it reaches the unsealed portion 6, the front sheet 2 and the back sheet 3 in the unsealed portion 6 open, forming an opening 10 as shown in FIG. 5( b) . This opening 10 functions as a pressure reduction port (hereinafter referred to as the "pressure reduction port 10") that releases the pressure in the internal space 4 before it excessively increases. In this way, the pressure in the internal space 4 can be released through the pressure reduction port 10 before it excessively increases. This prevents the package 1 from bursting or the contents M from spraying out of the package 1. A package 1 equipped with such a pressure reduction port 10 is suitable for cooking in a microwave oven MO.

[0072] The pressure in the internal space 4 is reduced by releasing the pressure in the internal space 4 through the pressure reduction port 10. As a result, the top sheet 2, which does not contain paper and / or pulp and is mainly composed of resin, shrinks as the internal pressure in the internal space 4 decreases, as shown in Figure 5(c). Meanwhile, the back sheet 3, which contains paper and / or pulp and is plastic, once deformed into an expanded shape, maintains that shape due to the shape-retaining properties (plasticity) of the paper and / or pulp. Thus, the back sheet 3 is maintained in a form capable of containing and holding the contents M, and can be used as a container.

[0073] After the heating process in the microwave oven MO is completed, the package 1 is removed from the microwave oven MO, and as shown in Figure 5(d), for example, the unsealed portion of the front sheet 2 outside the non-peripheral sealed portion 71 is pinched and peeled away from the back sheet 3. By at least partially separating the front sheet 2 and the back sheet 3 (in the example shown in Figure 5(d), approximately half of the front sheet 2 is separated from the back sheet 3), the contents M can be easily removed from the opening formed by the separation. Alternatively, as shown in Figure 5(e), the front sheet 2 may be completely separated from the back sheet 3. This separation of the front sheet 2 from the back sheet 3 can be easily performed because the sealant layer 51 (see Figure 3(b)) on the back sheet 3 also functions as an easy-peel layer. In addition, the peripheral seals 61 to 65 are provided so as to extend with a small gap from the edges of each side 31 to 34, and the non-peripheral seals 71 to 74 are provided at positions away from the four corners of the package 1, rather than along the edges of those corners. This makes it possible to prevent peeling at the interlayer between the base layer 52 and the paper layer 53 of the back sheet 3 when the front sheet 2 is separated from the back sheet 3.

[0074] FIG. 6 is a perspective view showing the back sheet 3 used as a container. As shown in FIG. 6, the back sheet 3 has lines 80 extending radially from the center of the back sheet 3 (the intersection of the diagonals of the back sheet 3) along the perpendicular bisectors of each of the sides 21 to 24. In other words, the back sheet 3 has lines 80 extending from the midpoints of the sides 21 to 24 toward the center of the package 1. The lines 80 have linear convex portions 80a that form fold peaks and linear concave portions 80b that form fold valleys. When the internal space 4 of the package 1 expands, the peripheral portions of the lines 80 bend, and the peripheral portions of the lines 80 rise in a folded state, using the lines 80 as folds. Therefore, by providing lines 80 at the desired folding locations on the back sheet 3, the back sheet 3 can be easily deformed into the desired container (tray) shape with a certain depth.

[0075] In this embodiment, the type of paper constituting the paper layer 53, the amount of pulp fiber, the amount of resin fiber mixed with the pulp fiber, the paper basis weight, the layer thickness, etc. are particularly set so that the back sheet 3 can maintain its container function for 5 minutes or more after the heat treatment. In this way, if the back sheet 3 maintains its container function for 5 minutes or more, the back sheet 3 can be used as a container as long as the food (contents M) is consumed.

[0076] The above describes the packaging body of the present invention based on one embodiment, but the present invention is not limited to the configuration described in the above embodiment, and the configuration can be changed as appropriate within the scope of the spirit of the present invention.

[0077] Alternative Embodiment 1 Figure 7 is an explanatory diagram of another embodiment of the heat-sealed portion 60. In the above embodiment, the non-peripheral sealed portions 71 to 74 are formed in an arc shape that bulges out toward the four corners of the package 1, in other words, in a direction away from the intersection of the diagonals of the package 1 (the center O of the package 1). However, this is not limited to this, and examples shown in Figures 7(a) and (b) are also possible. In the example shown in Figure 7(a), the non-peripheral sealed portions 71 to 74 are formed in an arc shape that bulges out toward the four corners of the package 1, in other words, in a arc shape that bulges out toward the intersection of the diagonals of the package 1 (the center O of the package 1). In the embodiment shown in Figure 7(b), the non-peripheral seal portions 71 to 74 are arranged so as to linearly connect the ends of adjacent peripheral seal portions 61, 63; 61, 64; 62, 63; 62, 65 at positions away from the four corners of the package 1, rather than along the edges of those corners.

[0078] Alternative Embodiment 2 Fig. 8 is an explanatory diagram of another embodiment of the ruled lines 80. In the above embodiment, an example was shown in which the ruled lines 80 were provided radially between an imaginary circle VC centered at the center O of the packaging body 1 and each of the sides 31 to 34, so as to be located on the perpendicular bisectors of each of the sides 31 to 34. However, this is not limited to this, and there is also an example shown in Fig. 8. In the example shown in Fig. 8, cross-shaped ruled lines 80 are provided so as to be located on the perpendicular bisectors of each of the sides 31 to 34 and to extend radially from the center O of the packaging body 1 to reach the edges of each of the sides 31 to 34. In other words, the ruled lines 80 are provided so as to connect the midpoint of side 31 with the midpoint of side 32 and to connect the midpoint of side 33 with the midpoint of side 34.

[0079] (Alternative embodiment 3) In the above-mentioned package 1, there is also an embodiment in which the front layer and the back layer are upside down, i.e., the front layer is made of a sheet similar to the back sheet 3, while the back layer is made of a sheet similar to the front sheet 2. In this case, it goes without saying that when used as a container, the front layer is used upside down. In another embodiment, both the front layer and the back layer are made of sheets containing paper and / or pulp similar to the back sheet 3.

[0080] (Alternative embodiment 4) In the above embodiment, an example was shown in which the outline of the packaging body 1 (top sheet 2, bottom sheet 3) in a planar view is rectangular (square), but this is not limited to this, and the outline in a planar view may be, for example, rectangular, triangular, polygonal with pentagons or more, circular, elliptical, etc.

[0081] Alternative Embodiment 5 Fig. 9 is an explanatory diagram of seal portions 91-93 attached to the peripheral seal portions 61-63. As shown in Fig. 9, in the area where the top sheet 2 and the back sheet 3 overlap in a plan view, seal portions 91-93 are attached to the peripheral seal portions 61-63, and are joined in a convex shape toward the inside of the area so as to overlap the crease 80. Here, the seal portions 91-93 are formed in a wedge-like shape that protrudes from the sides 31-33 along which the peripheral seal portions 61-63 extend toward the intersection of the diagonals of the package 1 (the center O of the package 1) at the position overlapping the crease 80 (hereinafter, the "seal portions 91-93" will be referred to as "wedge-shaped seal portions 91-93"). The sharp tips of the wedge-shaped seal portions 91-93 are positioned on the crease 80. By adopting such a configuration in which wedge-shaped seal portions 91 to 93 are provided, when the pressure in the internal space 4 rises and the internal space 4 expands, stress is concentrated at the sharp tips located on the lines 80 in the wedge-shaped seal portions 91 to 93, and therefore when the internal space expands, the portions surrounding the lines 80 are raised in a state where they are bent more deeply using the lines 80 as folds, thereby forming a deeper intended container shape.

[0082] 10 to 15 relating to the following alternative embodiments 6 to 11, the heat-sealed portion 60 is omitted from the illustration to facilitate understanding of the arrangement of the ruled lines 101 to 110. In FIGS. 10 to 15, the "first ruled line" and "convex ruled line" of the present invention are represented by a thick solid line, the "second ruled line" and "concave ruled line" of the present invention are represented by a thick outline line, and the "first ruled line" and "concave ruled line" of the present invention are represented by a thick dashed line. In the following alternative embodiments 6 to 12, as in the above-described embodiment, the front sheet 2 and the back sheet 3 in the package 1 have the same shape and area, and the front sheet 2 (front layer) and the back sheet 3 (back layer) overlap over the entire area of ​​the package 1 in a plan view. Therefore, the "center of the front layer and / or back layer" in the present invention is synonymous with the center of the package 1.

[0083] (Alternative Embodiment 6) Fig. 10 is an explanatory diagram of an arrangement example (1) of different types of ruled lines 101, 102, and 103. As shown in Fig. 10 , ruled lines 101 are formed on the packaging body 1 so as to extend linearly from the midpoints of sides 31 and 32 toward the center of the packaging body 1 and connect at the intersection of the diagonals of the packaging body 1 (center O of the packaging body 1), in other words, so as to linearly connect the midpoint of side 31 and the midpoint of side 32. Furthermore, ruled lines 102 are formed on the packaging body 1 so as to extend linearly from the midpoints of sides 33 and 34 toward the center of the packaging body 1 and have their ends located near the center O of the packaging body 1. Furthermore, multiple ruled lines 103 (four in this example) are formed on the packaging body 1 so as to surround the center of the packaging body 1, and when all of these ruled lines 103 are connected, each ruled line 103 surrounds the center of the packaging body 1 in a rectangular shape. A gap (preferably 5 mm or more) is provided between the ruled lines 101, 102 and the ruled line 103. The ruled lines 101, 102 are convex lines protruding toward the front sheet 2 (see FIG. 16(a)). The ruled line 103 is a concave line recessed toward the back sheet 3 (see FIG. 16(b)). The ruled lines 101, 102 correspond to the "first ruled line" and "convex ruled line" of the present invention. The ruled line 103 corresponds to the "second ruled line" and "concave ruled line" of the present invention.

[0084] Alternative Embodiment 7 FIG. 11 is an explanatory diagram of an arrangement example (2) of different types of creases 103 and 104. In this arrangement example (2), instead of the creases 101 and 102 in the arrangement example (1) shown in FIG. 10, multiple creases 104 (four in this example) are provided, as shown in FIG. 11. That is, in the package 1 shown in FIG. 11, the creases 104 are formed so as to extend linearly from the midpoints of the sides 31 to 34 toward the center of the package 1, with their ends positioned near the creases 103. The rest of the arrangement is the same as the arrangement example (1) shown in FIG. 10. A gap (preferably 5 mm or more) is provided between the creases 103 and 104. The creases 104 are convex lines (see FIG. 16(a)) that protrude toward the front sheet 2. The creases 104 correspond to the "first creases" and "convex creases" of the present invention.

[0085] Alternative Embodiment 8 FIG. 12 is an explanatory diagram of an arrangement example (3) of different types of creases 101, 102, and 105. In this arrangement example (3), instead of the creases 103 in the arrangement example (1) shown in FIG. 10, creases 105 are provided as shown in FIG. 12. That is, the package 1 shown in FIG. 12 has multiple creases 105 (four in this example) arranged around the center of the package 1, and when these creases 105 are connected, each crease 105 forms an oval shape surrounding the center of the package 1. The rest of the arrangement is the same as the arrangement example (1) shown in FIG. 10. A gap (preferably 5 mm or more) is provided between the creases 101 and 102 and the crease 105. The creases 105 are concave lines recessed toward the back sheet 3 (see FIG. 16(b)). The creases 105 correspond to the "second creases" and "concave creases" of the present invention.

[0086] 10 to 12 according to the sixth to eighth alternative embodiments, when the internal space 4 expands, the peripheral portions of the lines 101, 102, and 104 extending toward the center of the package 1 are raised in a folded state along the lines 101, 102, and 104, and the peripheral portions of the lines 103 and 105 extending to surround the center of the package 1 are raised in a folded state along the lines 103 and 105. This allows the package 1 to be reliably deformed into the intended container shape.

[0087] In addition, in the packages 1 of alternative embodiments 6 to 8, by providing convex creases 101, 102, and 104 that protrude toward the front sheet 2, when the internal space 4 of the package 1 expands, the packages 1 can be folded along the convex creases 101, 102, and 104 so that the peripheral portions of the creases 101, 102, and 104 protrude toward the inside of the container when the package 1 assumes its container shape. In addition, in the packages 1 of alternative embodiments 6 to 8, by providing concave creases 103 and 105 that are recessed toward the back sheet 3, when the internal space 4 of the package 1 expands, the packages 1 can be folded along the concave creases 103 and 105 so that the peripheral portions of the creases 103 and 105 protrude toward the outside of the container when the package 1 assumes its container shape. In this way, by appropriately combining the convex lines 101, 102, 104 and the concave lines 103, 105, it is possible to make the areas around the lines protrude in a balanced manner inside and outside the container, and the packaging body 1 can be deformed into a stable container shape.

[0088] (Alternative Embodiment 9) Fig. 13 is an explanatory diagram of an arrangement example (4) of different types of ruled lines 104, 106, and 107. As shown in Fig. 13, the package 1 has a plurality of (eight in this example) ruled lines 106 arranged around the center of the package 1 so as to surround the center of the package 1, and when all of these ruled lines 106 are connected, each ruled line 106 forms a rectangle surrounding the center of the package 1. Furthermore, the package 1 has ruled lines 104 formed so as to extend linearly from the midpoints of each of the sides 31 to 34 toward the center of the package 1, with their tips located near the ruled lines 106. Furthermore, the package 1 has a plurality of (four in this example) ruled lines 107 formed so as to extend linearly from each of the four corners of the package 1 (corners where the sides 31 to 34 intersect) toward the center of the package 1. The tip of the crease 107 facing the center of the package 1 is positioned slightly away from the center O of the package 1 and is within the area surrounded by the multiple creases 106. A gap (preferably 5 mm or more) is provided between the creases 104, 106, and 107. The creases 106 are concave lines recessed toward the back sheet 3 (see FIG. 16( b)). The creases 106 correspond to the "second creases" and "concave creases" of the present invention. The creases 107 are concave lines recessed toward the back sheet 3. The creases 107 correspond to the "first creases" and "concave creases" of the present invention. Note that the creases 107 shown as thick dashed lines in FIG. 13 are actually formed as continuous straight lines, and are represented as thick dashed lines for convenience in order to make them easier to distinguish from other types of creases (the same applies to the creases 109 described below).

[0089] (Alternative Embodiment 10) FIG. 14 is an explanatory diagram of an arrangement example (5) of different types of ruled lines 104, 106, 108, and 109. In this arrangement example 5, ruled lines 108 and 109 are provided as shown in FIG. 14 instead of the ruled line 107 shown in FIG. 13 . That is, the packaging body 1 is provided with a plurality of (four in this example) ruled lines 108 extending linearly from each corner toward the center of the packaging body 1 between the four corners of the packaging body 1 and the area surrounded by the plurality of ruled lines 106. Furthermore, the packaging body 1 is provided with a plurality of (eight in this example) ruled lines 109 extending linearly from each side 31 to 34 toward the center of the packaging body 1 between the adjacent ruled lines 104 and 108, and between each side 31 to 34 and the area surrounded by the plurality of ruled lines 106. The rest of the arrangement example is the same as the arrangement example (4) shown in FIG. 13 . A gap (preferably 5 mm or more) is provided between the creases 104, 108, 109 and the crease 106. The crease 108 is a concave line recessed toward the back sheet 3 (see FIG. 16(b)). The crease 108 corresponds to the "first crease" and "concave crease" of the present invention. The crease 109 is a concave line recessed toward the back sheet 3 (see FIG. 16(b)). The crease 109 corresponds to the "first crease" and "concave crease" of the present invention.

[0090] (Alternative embodiment 11) Fig. 15 is an explanatory diagram of an arrangement example (6) of different types of ruled lines 104, 106, and 110. In this arrangement example (6), instead of the ruled lines 107 shown in Fig. 13, four pairs of ruled lines 110 are provided, for a total of eight ruled lines 110, as shown in Fig. 15. That is, on the package 1, pairs of ruled lines 110 are formed between each of the four corners of the package 1 and the area surrounded by the multiple ruled lines 106, and are arranged in a figure-eight pattern such that the relative distance between the lines 110 gradually increases as one moves from each corner toward the center of the package 1. The rest of the arrangement is the same as the arrangement example (4) shown in Fig. 13.

[0091] In addition to the effects achieved by the packages 1 of the above-described alternative embodiments 6 to 8, the packages 1 of the above-described alternative embodiments 9 to 11 shown in Figures 13 to 15 can achieve the following effects. That is, in the above-described alternative embodiments 9 to 11, if the ruled lines 107 to 110 are provided to match the shape of the container when it is used as a container, when the internal space 4 expands, the package 1 can be raised in a folded state along the ruled lines 107 to 110, thereby ensuring that the package 1 can be deformed to match the shape of the container when it is used. In the above-described alternative embodiments 9 to 11, if the ruled lines 107 to 110 are provided to match the contents to be contained in the container, when the internal space 4 expands, the package 1 can be raised in a folded state along the ruled lines 107 to 110, thereby ensuring that the package 1 can be deformed to match the shape of the container when it is used.

[0092] The score lines 101, 102, 104, 107, 108, 109, and 110, which correspond to the first score lines of the present invention, and the score lines 103, 105, and 106, which correspond to the second score lines of the present invention, are not parallel to each other and do not intersect with each other. By adopting such a configuration, stress concentration between the score lines when the internal space 4 expands can be prevented.

[0093] (Alternative Embodiment 12) Figure 16 is an explanatory diagram relating to the height and width of the ruled lines 80, 101 to 110. As described above, the package 1 is manufactured by subjecting a laminated material sheet, which is made by overlapping and heat-sealing a material sheet for the front sheet 2 and a material sheet for the back sheet 3, to a punching process for punching out the outline and a process for carving the ruled lines 80, 101 to 110. Therefore, in the package 1, as shown in Figure 16(a) , the ruled lines 80, 101, 102, 104, 110 are configured by overlapping convex stripes on the front sheet 2 that protrude away from the back sheet 3 (upper side in Figure 16(a) ) and convex stripes on the back sheet 3 that protrude toward the front sheet 2, so that they are two sides of the same coin. As shown in Figure 16(b), in the package 1, the lines 103, 105, 106, 107, 108, and 109 are formed by overlapping concave lines recessed on the front sheet 2 toward the back sheet 3 and concave lines recessed on the side opposite the front sheet 2 (the lower side in Figure 16(b)) on the back sheet 3 so that they form one face and two faces.

[0094] 16(a) and 16(b), when the total thickness (total thickness) of the front sheet 2 and the back sheet 3 is T, and the protrusion (height) of the ruled lines 80, 101, 102, 104, and 110 from the surface of the front sheet 2 is h, or the protrusion (height) of the ruled lines 103, 105, 106, 107, 108, and 109 from the surface of the back sheet 3 is h, it is preferable to set the values ​​of h and T so as to satisfy the following formula (1): h ≧ 0.4T (1)

[0095] By setting the values ​​of h and T as described above, when the internal space 4 of the packaging body 1 expands, the areas around the lines 80, 101 to 110 can be reliably folded and raised along the lines 80, 101 to 110.

[0096] 16(a) and 16(b), the protrusion amount (height) h of the ruled lines 80, 101 to 110 is preferably 80 μm or more, and more preferably 100 μm or more. By doing so, when the internal space 4 of the package 1 expands, the areas around the ruled lines 80, 101 to 110 can be reliably folded and raised along the ruled lines 80, 101 to 110.

[0097] 16(a) and 16(b) preferably have a width (W) of 2 mm or more, so that when the internal space 4 of the package 1 expands, the areas around the lines 80, 101 to 110 can be reliably folded and raised along the lines 80, 101 to 110.

[0098] In the above embodiment and the other embodiment, the length of the creases 80, 101 to 110 is preferably 10 mm or more from the midpoint of each side 31 to 34 toward the center of the package 1. This allows the creases 80, 101 to 110 to be used as creases to reliably fold the periphery of the creases from the initial stage of rising of the periphery of the creases due to expansion of the internal space 4.

[0099] In the above-described other embodiment, the distance between the score lines 101, 102, 104, 107, 108, 109, and 110 (corresponding to the "first score lines" of the present invention) and the score lines 103, 105, and 106 (corresponding to the "second score lines" of the present invention) is set to 1 mm or more, and preferably 5 mm or more. This can prevent breakage due to stress concentration between the score lines when the internal space 4 expands.

[0100] <Method of Measuring Loop Stiffness> Figure 17 is an explanatory diagram of a method of measuring loop stiffness. In this specification, loop stiffness (resilience) refers to the repulsive force measured when a multilayer sheet (in this example, the back sheet 3) having at least a paper layer 53 (see Figure 3(b)) is formed into a loop-shaped sample piece 200 with a circumferential length of 100 mm, and the sample piece 200 is pressed toward a fixed plate 202 by a pressing plate 201 with a pressing length of 10 mm, as shown in Figure 17.

[0101] In the package 1, the loop stiffness measured by the above-mentioned measuring method is preferably 40 mN / 15 mm width or more, and more preferably 100 mN / 15 mm width or more.

[0102] By setting the loop stiffness to 40 mN / 15 mm width or more, the stiffness of the back sheet 3 is not too low, and a certain level of rigidity can be ensured after the package is deformed into the shape of a container, thereby ensuring sufficient functionality and durability as a container. There is no particular upper limit to the loop stiffness as long as the package functions as a container, but when considering the use of commonly available sheet materials as the material for the package, a realistic upper limit can be around 800 to 1000 mN / 15 mm width.

[0103] In the packaging body 1, the ratio (LS1 / LS2) of the loop stiffness (LS1) in the MD direction (the direction of papermaking) of the paper layer 53 to the loop stiffness (LS2) in the TD direction (the direction perpendicular to the direction of papermaking) of the paper layer 53 is preferably 1.0 to 1.5. Within this range, the stiffness of the back sheet 3 in the MD and TD directions is properly balanced, preventing uneven deformation in either the MD or TD direction and ensuring reliable deformation to the container shape. After deformation, the shape retention (plasticity) of the paper layer allows the packaging body 1 to maintain a stable container shape.

[0104] In the above embodiment and the other embodiment, a configuration may be adopted in which a gusset portion is provided between the front sheet 2 and the back sheet 3. By providing a gusset portion, the thickness of the side surface of the package 1 increases when the package 1 expands, making it possible to accommodate larger volumes.

[0105] Next, in order to confirm the effect of the packaging body 1 of the present invention, a heat treatment test was carried out using a microwave oven (Examples 1 to 3, Comparative Example 1).

[0106] As the package 1 of the above embodiment, packages according to Examples 1 to 3 were produced under the conditions shown in Table 1 below, and a package according to Comparative Example 1 was produced under the conditions shown in Table 1 below by forming both the front and back surfaces from plastic film, overlapping both plastic films, and heat-sealing the periphery. 50 g of water and two sheets of tissue paper were enclosed in each package as the contents M, and the package was heated in a microwave oven. The heating conditions were an output of 600 W and a heating time of 2 minutes and 30 seconds.

[0107]

[0108] After the heat treatment, the heights of the four corners (the corners where the sides 31 to 34 of the package 1 intersect) of the packages according to Examples 1 to 3 and Comparative Example 1 (heights H from the mounting surface S in FIG. 1(b)) were １ ~H ４ The smallest measured value was taken as the height of the package. Water was poured onto the back sheet 3 (the plastic film on the back surface) of the packages according to Examples 1 to 3 and Comparative Example 1, and the maximum amount of water that could be retained was measured. The results are shown in Table 2.

[0109]

[0110] In Example 1, in which neither the ruled lines 80 nor the wedge-shaped seal portions 91 to 93 were provided, when the internal space 4 expanded, the deformation of the back sheet 3 occurred naturally, and although it was difficult to deform it into the intended shape, it deformed into a shape that could function as a container for a certain amount of water (66.5 g), and this deformed shape was maintained for more than 5 minutes.

[0111] In Example 2, which did not have the wedge-shaped seals 91-93 but had the ruled lines 80, the water retention capacity (95.5 g) was equivalent to that of a typical paper plate (diameter: 180 mm, height: 15 mm, water retention capacity: 97.3 g). Furthermore, the deformed shape was maintained for more than 5 minutes. It is believed that the water retention capacity could be increased by providing the ruled lines 80 at the desired folding locations and forming the back sheet 3 into the intended deep container shape.

[0112] In Example 3, which had the wedge-shaped seals 91-93 in addition to the ruled lines 80, the amount of water retained (116.0 g) was greater than that of a typical paper plate. Furthermore, the deformed shape was maintained for more than 5 minutes. It is believed that the wedge-shaped seals 91-93 allowed for a deeper, more precise container shape, further increasing the amount of water retained.

[0113] In Comparative Example 1, both the top and bottom layers were initially deformed into an expanded shape due to the increase in internal pressure during heating, but after heating was completed, the expanded shape was not maintained and the container contracted due to the decrease in internal pressure, resulting in the container not being able to maintain its shape. As a result, as shown in Table 2, the height of the four corners of the package according to Comparative Example 1 was 0 mm, and the package was unable to hold water even when poured, resulting in a capacity of 0.0 g. The package according to Comparative Example 1 requires the contents to be transferred to another container after heating in a microwave oven, which is inconvenient.

[0114] Furthermore, as the packages 1 of the above-mentioned Alternative Embodiment 7 (see FIG. 11), Alternative Embodiment 10 (see FIG. 14), and Alternative Embodiment 11 (see FIG. 15), packages according to Examples 4 to 8 were produced under the conditions shown in Table 3 below. 50 g of water and two sheets of tissue paper were sealed in each package as the contents M, and the package was heated in a microwave oven. The heating conditions were an output of 600 W and a heating time of 2 minutes and 30 seconds. After the heating treatment, the heights of the four corners (corners where the sides 31 to 34 of the package 1 intersect) of the packages according to Examples 4 to 8 (height H from the mounting surface S in FIG. 1(b)) were １ ~H ４ The smallest measured value was taken as the height of the package. Water was also poured onto the back sheet 3 (the plastic film on the back surface) of the packages according to Examples 4 to 8, and the maximum amount of water that could be retained was measured. The results are shown in Table 3.

[0115]

[0116] As shown in Table 3, the packages 1 of Examples 4 to 8 include a score 104 corresponding to the first score of the present invention, and a score 103 or a score 106 corresponding to the second score of the present invention. This allows the packages 1 to be reliably deformed into the intended container shape. As long as the packages 1 of Examples 7 and 8 include score 103, 104 or score 104, 106, they can function as a container with a certain water retention capacity (49.0 g) (Example 8) or a container with a water retention capacity (93.9 g) equivalent to that of a typical paper plate (diameter: 180 mm, height: 15 mm, water retention capacity: 97.3 g) even though they do not include score 108, 109, or 110 (Example 7).

[0117] Example 5 includes creases 108 and 109 and satisfies the condition of formula (1), i.e., h / T is 0.4 or greater. Example 6 includes creases 110 and satisfies the condition of h / T is 0.4 or greater. In Examples 5 and 6, when the internal space 4 expands, the package 1 can be reliably deformed to the shape of the container when in use, or to the shape of the container that matches the contents. Furthermore, the package height can be increased compared to Examples 2 and 3, resulting in a water retention capacity greater than that of a typical paper plate, as well as a water retention capacity greater than that of Examples 2 and 3 (Example 2: 95.5 g, Example 3: 116.0 g, Example 5: 126.2 g, Example 6: 155.9 g). It is believed that the provision of creases 108, 109, and 110 allows the container to be formed into a deeper, more desirable container shape, further increasing the water retention capacity.

[0118] In Example 4, h / T was less than 0.4 and the line height h was 80 μm or greater, resulting in a water retention amount (80.4 g) greater than the water retention amount (66.5 g) of Example 1, which did not have line 80. If the line height h was 80 μm or greater, the functions of line 104, 106, 108, and 109 could be fully exerted, and it is believed that when internal space 4 expands, the areas around the line can be reliably folded and raised along line 104, 106, 108, and 109.

[0119] In Example 7, h / T was less than 0.4 and the line height h was less than 80 μm, but the line width W was 2.0 mm, resulting in a water retention capacity (93.9 g) equivalent to that of a typical paper plate (diameter: 180 mm, height: 15 mm, water retention capacity: 97.3 g). It is believed that if the line width W is 2.0 mm or more, the function of the lines 103 and 104 can be fully exerted, and when the internal space 4 expands, the areas around the lines can be reliably folded and raised along the lines 103 and 104.

[0120] In Example 8, the h / T ratio was less than 0.4, the crease height h was less than 80 μm, and the crease width W was less than 2.0 mm, but the container was deformed into a shape that could function as a container with a certain amount of water retention (49.0 g). By satisfying one or more of the three conditions (h / T of 0.4 or more (Condition 1), the crease height h of 100 μm or more (Condition 2), and the crease width W of 2.0 mm or more (Condition 3) (Examples 4 to 7), the functions of the creases 103, 104, 106, 108, 109, and 110 can be fully exerted, and the amount of water retention can be improved.

[0121] Furthermore, packages according to Examples 9 to 13 were prepared under the conditions shown in Table 4 below, with a configuration basically similar to that of the package of Example 1. After heat treatment, water was poured onto the back sheet 3 (the plastic film on the back surface) of the packages according to Examples 9 to 13, the maximum amount of water that could be held was measured, and the container-retaining performance was evaluated based on the following evaluation criteria, as in Examples 4 to 8. The evaluation results are shown in Table 4. The evaluation criteria for container-retaining performance, indicated by the symbols A and B in Table 4, are as follows:

[0122] <Evaluation criteria> A: Water retention amount is 72 g or more B: Water retention amount is 40 g or more but less than 72 g

[0123]

[0124] As shown in Table 4, the loop stiffness (LS1, LS2) values ​​of the packages of Examples 9 to 13 were within the numerical range specified by the present invention (40 mN / 15 mm width or more). If the loop stiffness value was 40 mN / 15 mm width or more, the package could be deformed into a shape that could function as a container for a certain amount of water retention (40 g or more), and the deformed shape could be maintained for 5 minutes or more. If the loop stiffness (LS1, LS2) value was 100 mN / 15 mm width or more, the container retention performance was evaluated as "A," and the amount of water retention could be further increased. From this, it can be said that a loop stiffness value of 100 mN / 15 mm width or more is more preferable.

[0125] As shown in Table 4, in the packages of Examples 9 to 13, the ratio (LS1 / LS2) of the loop stiffness (LS1) in the MD direction of the paper layer 53 to the loop stiffness (LS2) in the TD direction of the paper layer 53 was within the numerical range specified in the present invention (1.0 to 1.5). In the packages of Examples 9 to 13, the back sheet 3 deformed in a balanced manner without bias in either the MD or TD direction, and was able to reliably deform into the container shape. Furthermore, after deformation, the shape retention (plasticity) of the paper layer allowed the package to maintain a stable container shape.

[0126] The packaging body of the present invention can be suitably used as a food container for heating, which encloses food to be cooked in a microwave oven.

[0127] REFERENCE SIGNS LIST 1 Package 2 Surface layer (surface sheet) 3 Back layer (back sheet) 4 Internal space 10 Vacuum opening 51 Sealant layer 53 Paper layer 60 Heat-sealed portion 61-65 Peripheral seal portion 71-74 Non-peripheral seal portion 80 Creases (first crease, convex crease) 91-93 Wedge-shaped seal portion 101 Creases (first crease, convex crease) 102 Creases (first crease, convex crease) 103 Creases (second crease, concave crease) 104 Creases (first crease, convex crease) 105 Creases (second crease, concave crease) 106 Creases (second crease, concave crease) 107 Creases (first crease, concave crease) 108 Creases (first crease, concave crease) 109 Ruled line (first ruled line, concave ruled line) 110 Ruled line (first ruled line, convex ruled line)

Claims

1. A heat-treatable package having an expandable internal space surrounded by a surface layer and a backing layer, wherein at least one of the surface layer and the backing layer contains paper and / or pulp, and the package is configured so that it can be used as a container after heat treatment.

2. The package according to claim 1, wherein the outer layer and the inner layer are at least partially separable after heat treatment.

3. The package according to claim 1, further comprising a pressure reducing port for preventing excessive pressure buildup in the internal space.

4. The package according to claim 1, wherein at least one of the outer layer and the inner layer is provided with a crease to form a fold when the internal space is expanded.

5. A package as described in claim 4, wherein the lines include a first line extending in a direction toward the center of the front layer and / or the back layer, and a second line extending so as to surround the center of the front layer and / or the back layer.

6. The package according to claim 5, wherein the first and second scores are not parallel to each other and do not intersect.

7. The packaging body according to claim 4, wherein the lines include convex lines protruding toward the front layer side and concave lines recessed toward the back layer side.

8. The package according to claim 4, wherein the ruled lines are provided to match the shape of the container when in use.

9. The package according to claim 4, wherein the ruled lines are provided to match the contents to be contained in the container.

10. The packaging body according to claim 4, which is configured to satisfy the relationship h ≧ 0.4T, where T is the total thickness of the front layer and the back layer, and h is the amount by which the ruled lines protrude from the front layer or the back layer.

11. The package according to claim 4, wherein the amount of protrusion of the ruled lines from the front layer or the back layer is 80 μm or more.

12. A package as described in claim 4, wherein in the area where the front layer and the back layer overlap in a plan view, a seal portion is provided that joins the layers in a convex shape toward the inside of the area so as to overlap the line.

13. A package as described in claim 1, in which a seal portion is provided in the area where the front layer and the back layer overlap in a plan view, having a portion that is joined along the edge of the area and a portion that is joined not along the edge of the area.

14. The packaging body according to claim 1, wherein the surface layer and / or the back layer is a multi-layer sheet having a sealant layer containing a resin and a paper layer containing the paper and / or the pulp.

15. The packaging body according to claim 1, wherein the outer layer and the inner layer are configured to have different rigidities.

16. The package according to claim 1, which can maintain the shape that functions as a container for 5 minutes or more after heat treatment.

17. The packaging body according to claim 1, wherein the surface layer and / or the back layer is a multi-layer sheet having at least a paper layer containing the paper and / or the pulp, and the multi-layer sheet is formed into a loop-shaped sample piece having a circumference of 100 mm, and the loop stiffness measured when the sample piece is pressed down to a pressing length of 10 mm is 40 mN / 15 mm width or more.

18. A packaging body according to claim 17, wherein the ratio (LS1 / LS2) of the loop stiffness (LS1) in the MD direction of the paper layer to the loop stiffness (LS2) in the TD direction of the paper layer is 1.0 to 1.

5.

19. The packaging body according to any one of claims 1 to 18, which is used as a food container for heating food to be cooked in a microwave oven.

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