Packaging

Abstract

The present invention provides a packaging material that can be used as a container after heat treatment and can be easily deformed into the intended shape. [Solution] A heat-treated packaging body 1 having an expandable internal space 4 surrounded by a surface layer 2 and a back layer 3, wherein at least one of the surface layer 2 and the back layer 3 contains paper and / or pulp, and is configured to be usable as a container after heat treatment, comprising an annular seal portion 50 that can join the surface layer 2 and the back layer 3 in a ring shape in a plan view, and a partial seal portion 70 that partially joins the surface layer 2 and the back layer 3 on the inner side of the annular seal portion 50.

Description

Technical Field

[0001] The present invention relates to a package capable of heat treatment.

Background Art

[0002] For example, a flat pouch that heats a packaging bag filled with contents such as food by placing it in a microwave oven is known (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 and a plastic film constituting the back surface of the pouch and heat-sealing the peripheral edge. In this plastic pouch, an opening is provided at a position away from the heat-sealed peripheral edge, and a steam vent seal portion is formed so as 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 water vapor or the like generated from the contents, and the pouch expands. As the pouch expands, the steam vent seal portion gradually peels off toward the opening, and when the peeling progresses until it reaches the opening, water vapor or the like is discharged to the outside through the opening, and the internal pressure of the pouch decreases.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The plastic pouch described in Patent Document 1 has both its front and back surfaces made of plastic film. Therefore, even if both the front and back surfaces of the pouch deform into an inflated shape due to the increase in internal pressure, this inflated shape is not maintained after heating, and the pouch shrinks due to the decrease in internal pressure. 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. Furthermore, the deformation during expansion is unpredictable, and it is difficult to deform it into an intended shape.

[0007] This invention has been made in view of the above problems, and aims to provide a packaging body that can be used as a container after heat treatment and can be easily deformed into an intended shape. [Means for solving the problem]

[0008] The characteristic configuration of the packaging according to the present invention, which solves the above problems, is: A heat-treated packaging body having an expandable internal space surrounded by a surface layer and a back layer, The surface layer and the back layer contain paper and / or pulp, and are configured to be usable as a container after heat treatment. An annular sealing portion that can join the surface layer and the back layer in an annular shape when viewed from above, A partial seal portion that partially joins the surface layer and the back layer on the inner side of the annular seal portion, The goal is to provide for it.

[0009] In this packaging structure, when the pressure in the internal space enclosed by the outer and inner layers increases due to heat treatment, the internal space expands, and consequently, the outer and inner layers deform into a bulging shape. With this packaging structure, since at least one of the outer and inner layers contains paper and / or pulp, once at least one of the outer and inner layers is deformed into a bulging shape, the shape retention (plasticity) of the paper and / or pulp maintains the deformed shape. In this way, at least one of the outer and inner layers is maintained in a form that can contain and hold the contents, and can be used as a container. Furthermore, with this packaging structure, a partial seal is provided on the inner side of the annular seal, so the partial seal is positioned closer to the center of the annular seal. When the internal space expands, a shorter distance from the center of the annular seal makes it easier to rise, so the part with the partial seal can be raised relatively higher than the surrounding part. Therefore, by providing a partial seal in the area that you want to raise higher, the packaging can be easily deformed into the intended shape.

[0010] In the packaging according to the present invention, It is preferable that the partial sealing portion is formed to extend inward from the annular sealing portion while being connected to it.

[0011] With this packaging configuration, as the partial seal portion is raised higher relative to its surrounding portion, the annular seal portion to which the partial seal portion is connected can also be raised higher relative to its surrounding portion.

[0012] In the packaging according to the present invention, Let i be the shortest distance between the leading edge of the partial seal portion in the extending direction and the annular seal portion, and let L be the inner dimension of the annular seal portion in the extending direction of the partial seal portion. It is preferable that the ratio (i / L) × 100 of the shortest distance (i) to the inner dimension (L) is set to 3.0 to 23.0.

[0013] If the ratio (i / L) × 100 is extremely small, the distance between the leading edge of the partial seal portion in the extending direction and the center of the annular seal portion becomes excessively large, making it difficult to raise the portion with the partial seal portion higher relative to its surroundings. On the other hand, if the ratio (i / L) × 100 is extremely large, the distance between the leading edge of the partial seal portion in the extending direction and the center of the annular seal portion becomes excessively small, making it difficult to fill with contents. With this packaging configuration, the ratio (i / L) × 100 is set to 3.0 to 23.0, so the distance between the leading edge of the partial seal portion in the extending direction and the center of the annular seal portion becomes appropriate, allowing the portion with the partial seal portion to be raised higher relative to its surroundings, and enabling proper filling of contents.

[0014] In the packaging according to the present invention, It is preferable that the partial sealing portion is formed separately from the annular sealing portion.

[0015] With this packaging configuration, the partial seal portion can be raised higher relative to its surrounding portion, independently of the annular seal portion.

[0016] In the packaging according to the present invention, Let i be the shortest distance between the point on the outer contour of the partial seal portion closest to the center of the annular seal portion and the annular seal portion, and let L be the inner dimension of the annular seal portion in the direction of extension of the imaginary straight line connecting the point and the annular seal portion by the shortest distance (i). It is preferable that the ratio (i / L) × 100 of the shortest distance (i) to the inner dimension (L) is set to 3.0 to 23.0.

[0017] If the ratio (i / L)×100 is extremely too small, the distance between the point closest to the center of the annular seal portion on the outer contour of the partial seal portion and the center of the annular seal portion becomes excessively large, and it becomes difficult to raise the portion where the partial seal portion is provided relatively higher than its peripheral portion. On the other hand, if the ratio (i / L)×100 is extremely too large, the distance between the point closest to the center of the annular seal portion on the outer contour of the partial seal portion and the center of the annular seal portion becomes excessively small, and it becomes difficult to fill the contents. According to the package of the present configuration, since the ratio (i / L)×100 is set to 3.0 to 23.0, the distance between the point closest to the center of the annular seal portion on the outer contour of the partial seal portion and the center of the annular seal portion becomes appropriate, and the portion where the partial seal portion is provided can be raised relatively higher than its peripheral portion, and the contents can be filled appropriately.

[0018] In the package according to the present invention, a vapor-permeable seal portion is provided so as to be able to form a pressure-reducing port for suppressing an excessive pressure rise in the internal space, The partial seal portion is preferably disposed at a position facing the vapor-permeable seal portion with respect to the center of the annular seal portion.

[0019] When a pressure-reducing port for suppressing an excessive pressure rise in the internal space is formed, stress concentrates on the vapor-permeable seal portion as the internal pressure of the internal space rises. For this reason, when the internal space expands, the portion where the vapor-permeable seal portion is provided is raised relatively higher than its peripheral portion, and the vapor-permeable seal portion exhibits substantially the same function as the partial seal portion. According to the package of the present configuration, since the partial seal portion is disposed at a position facing the vapor-permeable seal portion with respect to the center of the annular seal portion, the portion where the partial seal portion is provided and the portion where the vapor-permeable seal portion is provided can be raised in a balanced manner with respect to the center of the annular seal portion.

[0020] In the package according to the present invention, The partial seal portions are preferably disposed at positions facing each other with the center of the annular seal portion interposed therebetween.

[0021] According to the package of this configuration, the part provided with the partial seal parts arranged at positions facing each other across the center of the annular seal part can be balancedly raised with reference to the center of the annular seal part.

[0022] In the package according to the present invention, It is preferably used as a food container for heating for enclosing food cooked by heating in a microwave oven.

[0023] According to the package of this configuration, at least one of the surface layer and the back layer can be used as a container capable of accommodating and holding food by expanding the internal space with water vapor or the like generated from the food by heat cooking in a microwave oven.

Brief Description of the Drawings

[0024] [Figure 1] FIG. 1 is a perspective view showing a package according to an embodiment of the present invention. [Figure 2] FIG. 2 is an explanatory view of the laminated structure of the front sheet and the back sheet. [Figure 3] FIG. 3 is an explanatory view of the structure of the package. [Figure 4] FIG. 4 is a model view in which the annular seal part and the partial seal part are simplified. [Figure 5] FIG. 5 is an explanatory view of the procedure when using as a food container for heating. [Figure 6] FIG. 6 is a perspective view showing a state where the back sheet is used as a container. [Figure 7] FIG. 7 is an explanatory view of another embodiment (1) of the heat seal part. [Figure 8] FIG. 8 is an explanatory view of another embodiment (2) of the heat seal part. [Figure 9] FIG. 9 is an explanatory view of another embodiment (3) of the heat seal part.

Mode for Carrying Out the Invention

[0025] The present invention will be described below with reference to the drawings. In the following embodiments, a packaging body used as a food container for heating food (contents M) to be heated in a microwave oven will be used as an example. However, the present invention is not intended to be limited to the embodiments and configurations shown in the drawings described below, or to the examples. In Figures 1 to 3, 5 and 6, the thickness of the surface layer 2 and the back layer 3, and the thickness relationships of the multiple layers 2a, 2b, 3a to 3d that make up each layer 2 and 3 have been exaggerated or simplified as appropriate, and do not strictly reflect the actual relative thicknesses (scale) of each layer.

[0026] <Outline configuration> Figure 1 is a perspective view showing a package 1 according to one embodiment of the present invention. Figure 1(a) is a perspective view showing the state of the package 1 containing contents M before inflation, and Figure 1(b) is a perspective view showing the state of the package 1 containing contents M after inflation. The package 1 shown in Figures 1(a) and (b) comprises a front layer 2 and a back layer 3, and has an expandable internal space 4 surrounded by the front layer 2 and the back layer 3. At least one of the front layer 2 and the back layer 3 contains paper and / or pulp, which is a type of molding sheet and / or molding filler, and is configured to be usable as a container after heat treatment. In the following description, an embodiment in which paper and / or pulp is included in the back layer 3 will be given as an example. In this embodiment, both the front layer 2 and the back layer 3 are made of sheet material, and in the following, "front layer 2" will be referred to as "front sheet 2" and "back layer 3" as "back sheet 3".

[0027] Figure 2 is an explanatory diagram of the laminated structure of the front sheet 2 and the back sheet 3. Figure 2(a) is a cross-sectional view showing the laminated structure of the front sheet 2. As shown in Figure 2(a), the front sheet 2 is a multilayer sheet in which a base layer 2a and a sealant layer 2b are laminated. The base layer 2a is located on the outside side of the packaging body 1. The sealant layer 2b is located facing the internal space 4 of the packaging body 1.

[0028] The base material layer 2a 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 for heating and cooking in a microwave oven. Examples of resin types include polyethylene terephthalate (PET), nylon film (Ny), polypropylene (PP), polyvinylidene chloride (PVDC), polyvinyl chloride (PVC), polymethylpentene (PMP), polyethylene (PE), etc. The resin film may be stretched. The resin film may also be a composite resin film made by laminating two or more of these resins. The thickness of the base material layer 2a is preferably 10 to 200 μm, and more preferably 20 to 150 μm.

[0029] The sealant layer 2b constituting the front sheet 2 is not particularly limited as long as it is a heat-adhesive resin that does not affect the contents and is a resin film that can be used as food packaging material for food that is generally 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, as well as polyethylene and polybutene blend resins, homopolypropylene resin (PP), propylene-ethylene random copolymer, propylene-ethylene block copolymer, and propylene-α-olefin copolymer. The resin film may also be a composite resin film obtained by laminating two or more of these resins. The front sheet 2 may also include a paper-like layer containing paper and / or pulp, as described later. The thickness of the sealant layer 2b is preferably 20 to 80 μm, and more preferably 30 to 50 μm.

[0030] <Backing sheet> Figure 2(b) is a cross-sectional view showing the laminated structure of the backing sheet 3. As shown in Figure 2(b), the backing sheet 3 has a sealant layer 3a, a base material layer 3b, a paper-like layer 3c, and an overprint varnish layer (hereinafter referred to as the "OP varnish layer") 3d. With the paper-like layer 3c as the reference, the base material layer 3b and the sealant layer 3a are sequentially laminated on one side of the paper-like layer 3c toward the internal space 4 of the packaging body 1, while the OP varnish layer 3d is laminated on the other side of the paper-like layer 3c toward the outside of the packaging body 1.

[0031] The sealant layer 3a of the backing sheet 3, like the sealant layer 2b of the fronting sheet 2, is required to have heat-sealing performance and no effect on the contents, as well as to function as an easy-peel layer. The sealant layer 3a 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. In particular, ethylene-vinyl acetate copolymer (EVA) can be preferably used as resin A. Resin B can be polypropylene (PP) or polybutylene (PB). Polypropylene (PP) can be random copolymer, homopolymer, block copolymer, etc., and among these, random copolymer can be preferably used. The thickness of the sealant layer 3a is preferably 20 to 80 μm, and more preferably 30 to 50 μm.

[0032] The base material layer 3b of the backing sheet 3 can be the same resin film as the base material layer 2a of the fronting sheet 2. However, the type of resin used may differ between the base material layer 3b of the backing sheet 3 and the base material layer 2a of the fronting sheet 2. The thickness of the base material layer 3b is preferably 5 to 50 μm, and more preferably 10 to 30 μm.

[0033] <Paper layer> The paper-based layer 3c is a structural layer containing paper and / or pulp. The paper-based layer 3c may be any paper containing 50% or more pulp fibers (cellulose fibers), or it may be a mixed paper containing resin fibers in addition to pulp fibers. The type of paper constituting the paper-based layer 3c is not particularly limited. Examples of paper types include single-sided gloss kraft paper, double-sided gloss kraft paper, water-resistant paper, oil-resistant paper, and cup base paper. Of these, single-sided gloss kraft paper and double-sided gloss kraft paper are preferred in terms of strength, bending resistance, and printability. The basis weight of the paper used in the paper-based layer 3c is 30-400 g / m². 2 It is 50-300g / m² 2 Preferably, it is 50-120 g / m² 2 It is more preferable that this be the case. In this example, the basis weight of the paper is 120 g / m². 2 The thickness of the paper layer 3c is preferably 20 to 800 μm, and more preferably 40 to 600 μm.

[0034] The OP varnish layer 3d functions as a coating layer covering the paper layer 3c, and is made of 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 copolymer, as well as silicone resins, acrylic resins, epoxy resins, polyester resins, cellulose resins, and urethane resins.

[0035] As described above, the backing sheet 3 is constructed by laminating a sealant layer 3a, a base material layer 3b, a paper-like layer 3c, and an OP varnish layer 3d, and is a multilayer sheet having at least a sealant layer 3a and a paper-like layer 3c. Therefore, it is possible to ensure thermal sealing properties by the sealant layer 3a, and to ensure the shape retention (plasticity) of the backing sheet 3 after deformation by the paper-like layer 3c.

[0036] The method for producing a laminate by laminating the base material layer 2a and sealant layer 2b constituting the front sheet 2, and the sealant layer 3a, base material layer 3b, paper-like layer 3c and OP varnish layer 3d constituting the back sheet 3, is not particularly limited. A laminate can be produced by laminating multiple layers simultaneously or sequentially. For example, a film with each layer can be produced at once by co-extrusion using an extruder equipped with a die, using existing methods such as the T-die method or the tubular method. Alternatively, the resin, paper, etc. constituting each layer can be separately formed into sheets, and then sequentially produced by laminating them using methods such as wet lamination, hot-melt lamination, dry lamination, press lamination, or extrusion lamination.

[0037] The front sheet 2 and the back sheet 3 are configured such that their rigidity (elastic modulus) differs from each other, depending on the type and thickness of the constituent materials of each layer that make up the front sheet 2 and the back sheet 3. In this example, the back sheet 3, which includes the paper layer 3c, is made to have higher rigidity than the front sheet 2. This allows the front sheet 2, which has relatively lower rigidity than the back sheet 3, to deform significantly, and the deformed back sheet 3 can then be used as a container.

[0038] Figure 3 is a diagram illustrating the structure of the packaging 1. Figure 3(a) is an exploded perspective view of the packaging 1 before heat sealing. Figure 3(b) is a perspective view showing the state in which the front sheet 2 and back sheet 3 are not joined in at least part before the contents M are placed in the internal space 4. Figure 3(c) is a perspective view showing the state in which the front sheet 2 and back sheet 3 are completely joined in an annular shape after the contents M are placed in the internal space 4.

[0039] As shown in Figure 3(a), the front sheet 2 has a rectangular (square) outline in plan view and has a first pair of opposite sides (sides 11 and 12) which are parallel and facing each other, and a second pair of opposite sides (sides 13 and 14) which are perpendicular to the first pair of opposite sides 11 and 12 and are parallel and facing each other. The back sheet 3, like the front sheet 2, has a rectangular (square) outline in plan view and has approximately equal area and has a first pair of opposite sides (sides 21 and 22) which are parallel and facing each other, and a second pair of opposite sides (sides 23 and 24) which are perpendicular to the first pair of opposite sides 21 and 22 and are parallel and facing each other.

[0040] <Heat seal section> As shown in Figures 3(b) and (c), the packaging 1 includes a heat-sealed portion 40 in which the necessary parts of the front sheet 2 and the back sheet 3 are joined by heat fusion when the front sheet 2 and the back sheet 3 are superimposed so that their first pair of opposite sides 11,12;21,22 and their second pair of opposite sides 13,14;23,24 coincide in a plan view. The heat-sealed portion 40 includes an annular seal portion 50 that can join the front sheet 2 and the back sheet 3 in an annular shape in a plan view, and a partial seal portion 70 that can partially join the front sheet 2 and the back sheet 3 on the inner side of the annular seal portion 50.

[0041] <Annular seal section> The annular seal portion 50 includes a form in which, before the contents M are placed in the internal space 4, the front sheet 2 and the back sheet 3 are not joined in at least a portion, and the front sheet 2 and the back sheet 3 are joined in an annular (C-shaped, C-ring-shaped) form with a portion open in a plan view, as shown in Figure 3(b) (hereinafter referred to as the "pre-sealing form"), and a form in which, after the contents M are placed in the internal space 4, the front sheet 2 and the back sheet 3 are joined in a completely annular (square annular) form in a plan view, as shown in Figure 3(c) (hereinafter referred to as the "post-sealing form").

[0042] The annular seal portion 50 in its pre-sealed state, as shown in Figure 3(b), is formed by heat-sealing the necessary parts (the parts where the peripheral seal portions 51, 53-55 and non-peripheral seal portions 61-64, as well as the vapor-permeable seal portion 56, are provided) excluding a predetermined area between the two opposite sides 12 and 22 that becomes the filling opening 5 for the contents M (the part where the peripheral seal portion 52 and partial seal portion 73, described later, are provided). Then, in Figure 3(b), after filling the internal space 4 between the front sheet 2 and the back sheet 3 with the contents M, the predetermined area between the two opposite sides 12 and 22 (the part where the peripheral seal portion 52 and partial seal portion 73, described later, are provided) is heat-sealed to close the filling opening 5, resulting in the sealed packaging 1 shown in Figure 3(c). On the front sheet 2 of the packaging 1, ridges emerge from the center of the sheet toward the four corners as the contents M are sealed. In this packaging 1, the first pair of opposite sides (sides 31 and 32) includes the first pair of opposite sides 11 and 12 on the front sheet 2 and the first pair of opposite sides 21 and 22 on the back sheet 3. Also, in this packaging 1, the second pair of opposite sides (sides 33 and 34) includes the second pair of opposite sides 13 and 14 on the front sheet 2 and the second pair of opposite sides 23 and 24 on the back sheet 3.

[0043] The annular seal portion 50 in its sealed form, as shown in Figure 3(c), includes peripheral seal portions 51-55 and non-peripheral seal portions 61-64. The peripheral seal portions 51-55 are provided to extend along the edges of each side 31-34, with a slight gap between them and the edges, in a length region shorter than the length of each side 31-34, based on the midpoint of each side 31-34 of the packaging body 1. The non-peripheral seal portions 61-64 are provided at positions away from the corners of the four corners of the packaging body 1 (the corners where sides 31-34 intersect), not along the edges of those corners, to connect the ends of adjacent peripheral seal portions 51,53;51,54;52,53;52,55. In this example, the non-peripheral seal portions 61-64 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 away from the intersection of the diagonals of the packaging body 1 (center O of the packaging body 1) (see Figure 4). In the following explanation, the portion including the intersection of the diagonals of the packaging body 1 (center O of the packaging body 1) will be referred to as the center of the packaging body 1.

[0044] The annular seal portion 50 further includes a vapor-permeable seal portion 56 provided between the peripheral seal portion 54 and the peripheral seal portion 55. The vapor-permeable seal portion 56 is provided in such a way that it can form a pressure-reducing port 10, which will be described later, to suppress an excessive pressure rise in the internal space, and is formed in a V-shape that protrudes toward the center of the packaging body 1 from the edge 34 along which the peripheral seal portions 54 and 55 are provided. Between the vapor-permeable seal portion 56 and the edge 34, there is an unsealed portion 6 where the front sheet 2 and the back sheet 3 are not heat-sealed.

[0045] <Partial sealing area> In the sealed form shown in Figure 3(c), the partial seal portion 70 includes a first partial seal portion 71, a second partial seal portion 72, and a third partial seal portion 73. The first partial seal portion 71 is located on the perpendicular bisector of side 33 and is positioned opposite the vapor seal portion 56. The second partial seal portion 72 and the third partial seal portion 73 are positioned opposite each other with the center of the annular seal portion 50 (the center of the package 1) in between, with the second partial seal portion 72 located on the perpendicular bisector of side 31, while the third partial seal portion 73 is located on the perpendicular bisector of side 32. The first partial seal portion 71, the second partial seal portion 72, and the third partial seal portion 73 are all formed in a triangular shape (wedge shape) that tapers toward the center of the annular seal portion 50 so as to extend inward from the annular seal portion 50 while connected to it. Furthermore, the third partial seal portion 73, which is provided in the post-sealed form shown in Figure 3(c), is not provided in the pre-sealed form because it would hinder the filling of the contents M into the internal space 4 in the pre-sealed form shown in Figure 3(b). Instead, after filling the internal space 4 with the contents M, the peripheral seal portion 52 and the third partial seal portion 73 are provided simultaneously by heat-sealing a predetermined area between the two opposite sides 12 and 22 to close the filling opening 5, resulting in a sealed package 1 with the contents M sealed inside, as shown in Figure 3(c).

[0046] Figure 4 is a simplified model diagram of the annular seal portion 50 and the partial seal portion 70. In Figure 4, the shortest distance between the leading edge of the partial seal portion 70 in the extending direction and the annular seal portion 50 is i, and the inner dimension of the annular seal portion 50 in the extending direction of the partial seal portion 70 is L. In this case, if the ratio (i / L) × 100 of the shortest distance (i) to the inner dimension (L) is too small, the distance between the leading edge of the partial seal portion 70 in the extending direction and the center of the annular seal portion 50 becomes excessively large, making it difficult to raise the portion where the partial seal portion 70 is provided relatively higher than the surrounding portion. On the other hand, if the ratio (i / L) × 100 is too large, the distance between the leading edge of the partial seal portion 70 in the extending direction and the center of the annular seal portion 50 becomes excessively small, making it difficult to fill with contents M (see Figure 3(c)). Therefore, the ratio (i / L) × 100 is preferably set to 3.0 to 23.0, more preferably to 3.3 to 20.0, and even more preferably to 3.3 to 10.0. This ensures that the distance between the leading edge of the partial seal portion 70 in the extending direction and the center of the annular seal portion 50 is appropriate, allowing the portion where the partial seal portion 70 is provided to be raised relatively higher than the surrounding portion, and enabling proper filling of the contents M. In Figure 4, the dashed line indicated by the symbol "A" represents the boundary between the annular seal portion 50 and the partial seal portion 70.

[0047] Figure 5 is an explanatory diagram of the procedure when using the packaging as a food container for heating. When the packaging 1, configured as described above, is used as a food container for heating food (contents M) to be heated in a microwave oven MO, as shown in Figure 5(a), the packaging 1 containing the contents M is placed flat inside the microwave oven MO, the predetermined heating conditions (wattage, heating time, etc.) are set, and the start button (not shown) is pressed to start heating. As a result, the internal pressure of the internal space 4 surrounded by the front sheet 2 and back sheet 3 increases due to the steam generated from the contents M, and as shown in Figure 5(b), the internal space 4 of the packaging 1 expands, and along with the expansion of the internal space 4, both the front sheet 2 and back sheet 3 are deformed into an inflated shape.

[0048] In the packaging 1, a partial seal portion 70 is provided on the inner side of the annular seal portion 50, so the partial seal portion 70 is positioned closer to the center of the annular seal portion 50. When the internal space 4 expands, a shorter distance from the center of the annular seal portion 50 makes it easier to rise, so the portion where the partial seal portion 70 is provided can be raised relatively higher than the surrounding portion. Therefore, by providing a partial seal portion 70 in the area that you want to be raised higher, the packaging 1 can be easily deformed into the desired shape.

[0049] As the internal pressure in the internal space 4 increases, stress concentrates at the tip of the steam seal portion 56 (see Figure 3(c)) that protrudes toward the center O of the packaging body 1. As a result, the steam seal portion 56 gradually peels away toward the unsealed portion 6 (see Figure 3(c)), and when the peeling progresses to reach the unsealed portion 6, the front sheet 2 and back sheet 3 in the unsealed portion 6 open up, forming an opening 10 as shown in Figure 5(b). This opening 10 functions as a pressure relief port (hereinafter referred to as "pressure relief port 10") that releases the pressure in the internal space 4 before the pressure in the internal space 4 rises excessively. In this way, the pressure in the internal space 4 can be released through the pressure relief port 10 before the pressure in the internal space 4 rises excessively. As a result, it is possible to prevent the packaging body 1 from bursting or the contents M from being blown out of the packaging body 1. A packaging body 1 equipped with such a pressure relief port 10 is suitable for heating and cooking in a microwave oven MO.

[0050] When the pressure relief port 10 is formed to suppress an excessive pressure rise in the internal space 4, stress concentrates in the steam seal portion 56 as the internal pressure of the internal space 4 rises. As a result, when the internal space 4 expands, the portion where the steam seal portion 56 is provided is raised relatively higher than the surrounding portion, and the steam seal portion 56 performs substantially the same function as the partial seal portion 70.

[0051] By releasing the pressure in the internal space 4 through the pressure relief port 10, the internal pressure of the internal space 4 decreases. As a result, the outer sheet 2, which is mainly composed of resin and does not contain paper and / or pulp, shrinks in response to the decrease in internal pressure in the internal space 4, as shown in Figure 5(c). On the other hand, the inner sheet 3, which is composed of paper and / or pulp, is plastic, so once it is deformed into an inflated shape, the shape retention (plasticity) of the paper and / or pulp maintains the deformed shape. In this way, the inner sheet 3 is maintained in a form that can contain and hold the contents M, and can be used as a container.

[0052] Once the heating process in the microwave oven is complete, remove the package 1 from the microwave oven, and as shown in Figure 5(d), pinch the unsealed portion of the front sheet 2 outside the non-peripheral seal portions 61-64 and peel it away from the back sheet 3. By separating the front sheet 2 and the back sheet 3 in at least a portion (in the example shown in Figure 5(d), the front sheet 2 is separated about halfway 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 operation of the front sheet 2 from the back sheet 3 can be easily performed because the sealant layer 3a on the back sheet 3 (see Figure 3(b)) also functions as an easy-peel layer. In addition, the peripheral sealing portions 51-55 are provided so as to extend with a slight gap from the edges of each side 31-34, and the non-peripheral sealing portions 61-64 are provided at positions away from the corners of the four corners of the packaging body 1, rather than along the edges of those corners. Therefore, when separating the front sheet 2 from the back sheet 3, it is possible to prevent delamination at the interlayer portion between the base material layer 3b and the paper layer 3c of the back sheet 3.

[0053] Figure 6 is a perspective view showing the backing sheet 3 in use as a container. As shown in Figure 6, in the backing sheet 3, the portion where the partial sealing portion 70 (first partial sealing portion 71, second partial sealing portion 72, third partial sealing portion 73) is provided, and the portion where the vapor-permeable sealing portion 56, which performs substantially the same function as the partial sealing portion 70, is provided, are raised relatively higher than the surrounding portion. Therefore, the backing sheet 3 can be easily deformed into a container-like (tray-like) shape with a certain depth.

[0054] In the packaging 1, the first partial seal portion 71 is positioned opposite the vapor-permeable seal portion 56 with respect to the center of the annular seal portion 50, so that the portion with the first partial seal portion 71 and the portion with the vapor-permeable seal portion 56 can be raised in a balanced manner with respect to the center of the annular seal portion 50. Furthermore, the second partial seal portion 72 and the third partial seal portion 73 are positioned opposite each other with respect to the center of the annular seal portion 50, so that the portions with the second partial seal portion 72 and the third partial seal portion 73, which are positioned opposite each other with respect to the center of the annular seal portion 50, can be raised in a balanced manner with respect to the center of the annular seal portion 50.

[0055] In this embodiment, the type of paper constituting the paper layer 3c, the amount of pulp fibers, the amount of resin fibers mixed with the pulp fibers, the basis weight of the paper, and the thickness of the layer are set so that the backing sheet 3 can maintain its container form for 5 minutes or more after heat treatment.

[0056] Although the packaging of the present invention has been described above based on one embodiment, the present invention is not limited to the configuration described in the above embodiment, and its configuration can be modified as appropriate without departing from the spirit of the invention.

[0057] (Another Embodiment 1) Figure 7 is an explanatory diagram of another embodiment (1) of the heat seal portion 40. In the above embodiment, an example was shown in which the non-peripheral seal portions 61 to 64 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 toward the intersection of the diagonals of the packaging body 1 (center O of the packaging body 1). However, it is not limited to this, and there are also embodiments shown in Figures 7(a) and (b). In the embodiment shown in Figure 7(a), the non-peripheral seal portions 61 to 64 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 toward the intersection of the diagonals of the packaging body 1 (center O of the packaging body 1). In the embodiment shown in Figure 7(b), the non-peripheral sealing portions 61 to 64 are provided so as to linearly connect the ends of adjacent peripheral sealing portions 51, 53; 51, 54; 52, 53; 52, 55 at positions away from the corners of the four corners of the packaging body 1, rather than along the edges of those corners.

[0058] (Another Embodiment 2) Figure 8 is an explanatory diagram of another embodiment (2) of the heat seal portion 40. In the above embodiment, the partial seal portion 70 (first partial seal portion 71, second partial seal portion 72, third partial seal portion 73) is shown as being formed in a triangular shape that tapers toward the center of the annular seal portion 50 so as to extend inward from the annular seal portion 50 while connected to the annular seal portion 50. However, it is not limited to this, and there is also the embodiment shown in Figure 8(a). In the embodiment shown in Figure 8(a), the partial seal portion 70 (first partial seal portion 71, second partial seal portion 72, third partial seal portion 73) is formed in a linear shape toward the center of the annular seal portion 50 so as to extend inward from the annular seal portion 50 while connected to the annular seal portion 50. In Figure 8(b), a simplified model diagram of the annular seal portion 50 and partial seal portion 70 in the embodiment example shown in Figure 8(a), the shortest distance between the leading edge of the partial seal portion 70 in the extending direction and the annular seal portion 50 is defined as i, and the inner dimension of the annular seal portion in the extending direction of the partial seal portion is defined as L. In this case, the ratio (i / L) × 100 of the shortest distance (i) to the inner dimension (L) is preferably set to 3.0 to 23.0, more preferably to 3.3 to 20.0, and even more preferably to 3.3 to 10.0.

[0059] (Another embodiment 3) Figure 9 is an explanatory diagram of another embodiment (3) of the heat seal portion 40. In the above embodiment, the partial seal portion 70 (first partial seal portion 71, second partial seal portion 72, third partial seal portion 73) is shown as being formed in a triangular shape that tapers toward the center of the annular seal portion 50 so as to extend inward from the annular seal portion 50 while connected to the annular seal portion 50. However, it is not limited to this, and there is also the embodiment shown in Figure 9(a). In the embodiment shown in Figure 9(a), the partial seal portion 70 (first partial seal portion 71, second partial seal portion 72, third partial seal portion 73) is formed in a spot shape (circular shape) on the inward side of the annular seal portion 50 while being separated from the annular seal portion 50. In Figure 9(b), a simplified model diagram of the annular seal portion 50 and partial seal portion 70 in the embodiment example shown in Figure 9(a), the shortest distance between the point closest to the center of the annular seal portion 50 on the outer contour of the partial seal portion 70 (the point indicated by the symbol "B" in Figure 9(b)) and the annular seal portion 50 is defined as i. The inner dimension of the annular seal portion 50 in the direction of extension of the imaginary straight line (the dashed line indicated by the symbol "C" in Figure 9(b)) connecting the point and the annular seal portion 50 by the shortest distance (i) is defined as L. In this case, the ratio (i / L) × 100 of the shortest distance (i) to the inner dimension (L) is preferably set to 3.0 to 23.0, more preferably to 3.3 to 20.0, and even more preferably to 3.3 to 10.0.

[0060] (Another Embodiment 4) In the above-described packaging 1, there is also a configuration in which the front layer and back layer are inverted, that is, 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 should be used inverted. There is also a configuration in which both the front and back layers are made of sheets containing paper and / or pulp similar to the back sheet 3.

[0061] (Another embodiment 5) In the above embodiment, an example was shown in which the plan view contour of the packaging 1 (front sheet 2, back sheet 3) is rectangular. However, the example is not limited to this, and the plan view contour may be, for example, triangular, a polygon with pentagons or more, circular, elliptical, etc.

[0062] (Another embodiment 6) In the above embodiment, an example was shown in which the outline of the annular seal portion 50 in plan view after encapsulation is a rectangular annular shape. However, the embodiment is not limited to this, and the outline in plan view may be, for example, a triangular annular shape, a polygonal annular shape with pentagons or more sides, a circular annular shape, an elliptical annular shape, etc. [Examples]

[0063] Next, to confirm the effects of the packaging 1 of the present invention, a heat treatment test using a microwave oven was conducted (Examples 1-5, Comparative Examples 1-4).

[0064] <Examples 1-5 and Comparative Examples 1-4> As packaging 1 of the above embodiment, packaging bodies according to Examples 1 to 5 were manufactured under the conditions shown in Table 1 below. In addition, packaging bodies according to Comparative Example 1 were manufactured under the conditions shown in Table 1 below by constructing both the front and back sides with plastic film, overlapping both plastic films, and heat-sealing the periphery. Furthermore, in Comparative Example 1, instead of the plastic film constituting the back side, a sheet material containing paper and / or pulp (corresponding to back sheet 3) was used, similar to packaging body 1 of the above embodiment, and packaging bodies according to Comparative Examples 2 to 4 were manufactured under the conditions shown in Table 1 below. Note that Examples 1 to 5 and Comparative Examples 1 to 4 shown in Table 1 below are listed in the order of those without a partial seal and those with a partial seal, and for those with a partial seal, they are listed in ascending order of (i / L) × 100.

[0065] <Testing Method> Each package was filled with 50g of water and two tissues and heated in a microwave oven. The heating conditions were 600W output and a heating time of 2 minutes and 30 seconds. After heating, the heights of the four corners of the packages for Examples 1-5 and Comparative Examples 1-4 (the corners where sides 31-34 intersect in package 1) (corresponding to the heights H1-H4 from the mounting surface S in Figure 1(b)) were measured, and the smallest measured value was taken as the height of the package. In addition, water was poured onto the back sheet 3 (plastic film on the back) of the packages for Examples 1-5 and Comparative Examples 1-4, and the maximum amount of water that could be held was measured. Furthermore, the act of filling each package with contents was performed 30 times to evaluate whether it could be filled properly. The criteria for evaluating the proper filling are as follows.

[0066] <Evaluation Criteria for Filling Appropriateness> Fully refillable 30 times: A 1 in 30 filling failures: B Filling failure 2 or more times out of 30: C Furthermore, one instance of filling failure (appropriate filling: B) out of 30 trials with a rating of B was considered not to be a problem in actual production.

[0067] Furthermore, a comprehensive evaluation was conducted based on the water retention capacity and filling suitability. The comprehensive evaluation criteria are as follows:

[0068] <Overall Evaluation Criteria> If the water content is 72.0g or more and the filling suitability evaluation is A or B: Suitable If the water content is less than 72.0g: Unsuitable Even if the water content is 72.0g or more, if the filling suitability evaluation is C: Unsuitable

[0069] Table 1 shows the measurement results of the package height and water content using the above test method, as well as the results of the filling suitability evaluation and overall evaluation.

[0070] [Table 1]

[0071] In Examples 1 to 5, where the ratio (i / L) × 100 of the shortest distance (i) to the inner dimension (L) is 3.0 or higher, the package height is greater and the water retention capacity is also greater compared to Comparative Example 3, where the ratio (i / L) × 100 is less than 3.0. If the ratio (i / L) × 100 is 3.0 or higher, the portion where the partial seal portion 70 is provided can be raised relatively higher relative to the surrounding portion, and the package 1 can be easily deformed into the intended shape. However, if the ratio (i / L) × 100 exceeds 23.0, as shown in the results of Comparative Example 4, the filling suitability evaluation becomes C, which hinders actual production. From these results, it can be said that it is preferable to set the ratio (i / L) × 100 between 3.0 and 23.0.

[0072] In Examples 1 to 5, since the water retention amount is 72.0 g or more and the filling suitability evaluation is A or B, it is more preferable to set the ratio (i / L) × 100 to 3.3 to 20.0. Furthermore, in Examples 1 to 3, since the water retention amount is 72.0 g or more and the filling suitability evaluation is A, it is even more preferable to set the ratio (i / L) × 100 to 3.3 to 10.0.

[0073] In Comparative Example 1, which lacked a partial seal, both the surface and back layers deformed into an inflated shape due to the increase in internal pressure during the heating process. However, after heating, this inflated shape was not maintained, and the container contracted due to the decrease in internal pressure, failing to retain its shape. As a result, as shown in Table 1, the height of the four corners of the packaging in Comparative Example 1 was 0 mm, and it could not hold water even when poured in, resulting in a capacity of 0 g. The packaging in Comparative Example 1 requires the contents to be transferred to another container after heating in a microwave oven, which is inconvenient.

[0074] Similarly, Comparative Example 2, which also lacked a partial seal, had a slightly larger package height compared to Comparative Example 3, which did have a partial seal. However, its water retention capacity was 66.5g, which was less than that of Comparative Example 3, which had a water retention capacity of 70.1g. This is likely because, in Comparative Example 2, the lack of a partial seal meant that deformation during internal expansion was left to chance, preventing the package from being deformed into the intended shape.

[0075] Comparative Example 3, despite having a partial seal, resulted in a lower packaging height than Comparative Example 2, which did not have a partial seal. This is likely because, in Comparative Example 3, the ratio (i / L) × 100 is less than 3.0, making it difficult to raise the portion with the partial seal higher than its surrounding area due to the excessively large distance between the leading edge of the partial seal and the center of the annular seal.

[0076] <Example 6 and Comparative Example 5> Even when the shape of the annular seal portion 50 in the packaging 1 of the above embodiment differs, tests were conducted to determine the effect of the presence or absence of the partial seal portion 70 on the packaging height and water retention capacity. In the above embodiment, the case in which the annular seal portion 50 is formed in a square ring shape was illustrated, but the packaging height and water retention capacity were measured in the case where the annular seal portion 50 is formed in a circular ring shape and a partial seal portion 70 is provided (Example 6), and in the case where the partial seal portion 70 is not provided (Comparative Example 5). The results are shown in Table 2.

[0077] [Table 2]

[0078] As shown in Table 2, Comparative Example 5, which does not have a partial seal portion 70, showed a smaller water retention capacity compared to Example 6, which does have a partial seal portion 70. This is thought to be because, in Comparative Example 5, since there is no partial seal portion 70, the deformation during expansion of the internal space is left to chance, and the package cannot be deformed into the intended shape. In contrast, in Example 6, the provision of a partial seal portion 70 allows the package to be easily deformed into the intended shape. Therefore, regardless of the shape of the annular seal portion 50, by providing a partial seal portion 70, the portion with the partial seal portion 70 can be raised relatively higher than the surrounding portion, allowing the package to be deformed into the intended shape and improving the water retention capacity. [Industrial applicability]

[0079] The packaging of the present invention is suitably usable as a food container for heating food that is to be cooked in a microwave oven. [Explanation of symbols]

[0080] 1 package 2. Surface layer (surface sheet) 3. Backing layer (back sheet) 4 Interior space 10 Pressure Reducing Port 50 Annular seal section 56 Steam sealing section 70 Partial sealing section

Claims

1. A heat-treated packaging body having an expandable internal space surrounded by a surface layer and a back layer, The surface layer and the back layer contain paper and / or pulp, and are configured to be usable as a container after heat treatment. An annular sealing portion that can join the surface layer and the back layer in an annular shape when viewed from above, A partial seal portion that partially joins the surface layer and the back layer on the inner side of the annular seal portion, A packaging body equipped with the following features.

2. The packaging according to claim 1, wherein the partial sealing portion is formed to extend inward from the annular sealing portion while being connected to the annular sealing portion.

3. Let i be the shortest distance between the leading edge of the partial seal portion in the extending direction and the annular seal portion, and let L be the inner dimension of the annular seal portion in the extending direction of the partial seal portion. The packaging according to claim 2, wherein the ratio (i / L) × 100 of the shortest distance (i) to the inner dimension (L) is set to 3.0 to 23.

0.

4. The packaging according to claim 1, wherein the partial sealing portion is formed separately from the annular sealing portion.

5. Let i be the shortest distance between the point on the outer contour of the partial seal portion closest to the center of the annular seal portion and the annular seal portion, and let L be the inner dimension of the annular seal portion in the direction of extension of the imaginary straight line connecting the point and the annular seal portion by the shortest distance (i), The packaging according to claim 4, wherein the ratio (i / L) × 100 of the shortest distance (i) to the inner dimension (L) is set to 3.0 to 23.

0.

6. A steam seal portion is provided so as to be able to form a pressure relief port to suppress an excessive pressure rise in the internal space. The packaging according to claim 1, wherein the partial sealing portion is positioned opposite the steam sealing portion with respect to the center of the annular sealing portion.

7. The packaging according to claim 1, wherein the partial sealing portions are arranged to face each other with the center of the annular sealing portion in between.

8. A packaging body according to any one of claims 1 to 7, used as a food container for heating food for use in a microwave oven.

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