Microwave packaging

Abstract

To provide a package for a microwave oven, which has a vapor discharge part that easily gets peeled off accompanying increase in internal pressure.SOLUTION: The package for a microwave oven is provided with a film-shaped lid part, a container main body, formed in a concave shape, which can store contents, a flange part provided to extend outward from an upper end of the container main body and a heat-welded part to which the lid part is heat-welded. The heat-welded part comprises a vapor discharge part, provided across a whole circumference of the flange part, which discharges vapor. The vapor discharge part is configured to curve a portion of the heat-welded part in a direction of an inner edge of the flange part. An average line width of the vapor discharge part is smaller than an average line width of the other site of the heat-welded part. When a length of a first line segment connecting a pair of roots at the inner edge side of the vapor discharge part is defined as L1, a point at which a straight line which is parallel to the first line segment and passing on a tip A of the vapor discharge part reaches the inner edge of the heat-welded part is defined as B, and a length of a second line segment connecting the tip A to the point B is defined as L2, a relational expression of L2 / L1≥1.0 is satisfied.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a package for a microwave oven.

Background Art

[0002] The package for a microwave oven of Patent Document 1 is configured such that when the internal pressure of the package rises due to heating in the microwave oven, the lid portion and the flange portion are separated at the steam discharge portion, and the steam is discharged.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the steam discharge portion disclosed in Patent Document 1 may be difficult to separate even when the internal pressure of the container increases. In such a case, the package may burst, or separation may occur at a site other than the steam discharge portion, and steam may be discharged from an unintended site.

[0005] The present invention has been made in view of such circumstances, and provides a package for a microwave oven having a steam discharge portion that is likely to separate as the internal pressure increases.

Means for Solving the Problems

[0006] According to the present invention, a microwave-safe packaging for storing contents in a sealed state comprises a film-like lid and a container sealed by the lid, the container having a concave container body capable of containing contents and an annular flange portion extending outward from the upper end of the container body, the flange portion having a heat-sealed portion formed by heat welding the flange portion and the lid portion, the heat-sealed portion being provided around the entire circumference of the flange portion, and the heat-sealed portion being generated by heating the contents in a microwave oven. A packaging body is provided which includes a steam discharge section for discharging steam, wherein the steam discharge section is formed by curving a part of the heat-welded section toward the inner edge of the flange section, the average line width of the steam discharge section is smaller than the average line width of the other parts of the heat-welded section, L1 is the length of a first line segment connecting a pair of roots on the inner edge side of the steam discharge section, B is the point where a straight line passing through the tip A of the steam discharge section and parallel to the first line segment reaches the inner edge of the heat-welded section, and L2 is the length of a second line segment connecting the tip A and point B, such that L2 / L1 ≥ 1.0.

[0007] The present invention is characterized by having a steam discharge section with the above configuration. Because the line width of the steam discharge section with this configuration is relatively thin, the peel strength is lower than that of parts other than the steam discharge section, and because the relationship L2 / L1 ≥ 1.0 exists, force is easily applied to the tip of the steam discharge section. For this reason, peeling is likely to occur at the steam discharge section as the internal pressure of the packaging increases.

[0008] The following are examples of various embodiments of the present invention. The embodiments shown below can be combined with each other. Preferably, the packaging is as described above, wherein the angle between the line segment connecting the tip A and the base and the line segment connecting the base and point B is 91 to 120 degrees. Preferably, the packaging is as described above, wherein the portion between the tip A and the base is curved so as to be convex toward the outer edge of the steam discharge portion. Preferably, the packaging is as described above, wherein the tip A is pointed. Preferably, the packaging described above is a packaging in which the heat-sealed portion is located adjacent to the steam discharge portion and has a transition portion in which the line width gradually narrows toward the steam discharge portion. Preferably, the packaging is as described above, wherein the heat-sealed portion is provided on the flat surface of the flange portion. Preferably, the packaging described above, wherein the container comprises a paper material layer and a resin layer bonded to the paper material layer. [Brief explanation of the drawing]

[0009] [Figure 1] This is a perspective view of a microwave oven packaging body 1 according to the first embodiment of the present invention. The dashed lines in the figure represent boundary lines where the curvature of the surfaces constituting the surface shape changes. The same applies to the other figures. [Figure 2] Figure 2A is a plan view of packaging 1 in Figure 1, and Figure 2B is a cross-sectional view of BB in Figure 2A. [Figure 3] This is a magnified view of region A in Figure 2. [Figure 4] Figure 4A is a perspective view of the area near the steam outlet 7, and Figure 4B is a corresponding figure to Figure 4A, showing the state in which the area 7c near the steam outlet 7 is bulging due to the increase in internal pressure of the packaging 1. [Figure 5] This is a perspective view illustrating the manufacturing method of packaging 1. [Figure 6] Figure 6A is a perspective view of the silver bar 9 in Figure 5, and Figure 6B is an enlarged view of region B in Figure 6A. [Figure 7] This is a plan view of a microwave oven packaging body 1 according to a second embodiment of the present invention. [Figure 8] This is an enlarged view of region A in Figure 7. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described below. The various features shown in the embodiments below can be combined with each other. Furthermore, each feature can stand alone as an independent invention.

[0011] 1. First Embodiment 1-1. Composition of microwave packaging 1 The microwaveable packaging 1 shown in Figures 1 to 4 is used to store contents F in a sealed state. This packaging 1 comprises a film-like lid 2 and a container 3 sealed by the lid 2. The contents F include foods that contain moisture and can be heated or cooked in a microwave oven, such as retort foods.

[0012] The container 3 has a container body 4 formed in a concave shape and capable of containing contents F, and an annular flange portion 5 provided so as to extend outward from the upper end 4a of the container body 4. The flange portion 5 is provided with a heat-sealed portion 6 where the flange portion 5 and the lid portion 2 are heat-sealed together. The heat-sealed portion 6 is provided around the entire circumference of the flange portion 5. As a result, the contents F are sealed inside the packaging body 1 by heat-sealing the flange portion 5 and the lid portion 2 at the heat-sealed portion 6.

[0013] The heat-sealed portion 6 is equipped with a steam discharge portion 7 for releasing steam generated when the contents F are heated in a microwave oven. The steam discharge portion 7 is a portion that is more easily peeled off than the other portions 6a of the heat-sealed portion 6, and as the internal pressure of the packaging 1 increases due to the heating of the contents F, the lid portion 2 and the flange portion 5 preferentially peel off at the steam discharge portion 7, thereby enabling the release of steam through the steam discharge portion 7. With this configuration, leakage of steam from unintended areas and the rupture of the packaging 1 due to insufficient steam release are suppressed.

[0014] The steam discharge section 7 is constructed by curving a portion of the heat-welded section 6 toward the inner edge 5a of the flange section 5. As a result, the steam discharge section 7 has a roughly V-shape. With this shape, the peeling force generated as the internal pressure of the package 1 increases tends to concentrate at the tip A of the steam discharge section 7, making peeling at the steam discharge section 7 even easier.

[0015] As shown in FIG. 3, the portion on the tip A side of the first line segment 7e connecting the pair of bases 7a on the inner edge side of the steam discharge portion 7 is the steam discharge portion 7. The average line width of the steam discharge portion 7 is smaller than the average line width of the other portion 6a of the heat welding portion 6. The average line width of the steam discharge portion 7 is calculated by dividing the area of the portion on the tip A side of the line segment 7e by the length in the longitudinal direction of the steam discharge portion 7. The average line width of the other portion 6a is calculated by dividing the area of the portion on the side away from the tip A from the base 7a by the length in the longitudinal direction of the other portion 6a. The longitudinal length is, in other words, the length of the center line in the line width direction. The value of {average line width of the steam discharge portion 7 / average line width of the other portion 6a} is, for example, 0.01 to 0.9 (0.20 in this embodiment, 0.16 in the second embodiment), preferably 0.05 to 0.5, and more preferably 0.1 to 0.4. Specifically, this value is, for example, 0.01, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, and may be within the range between any two of the numerical values exemplified here or any of them or less.

[0016] As shown in FIG. 3, taking the length of the first line segment 7e connecting the pair of bases 7a as L1, the point where a straight line passing through the tip A and parallel to the first line segment 7e reaches the inner edge of the heat welding portion 6 as B, and the length of the second line segment 7f connecting the tip A and the point B as L2, then L2 / L1 ≧ 1.0 (1.3 in this embodiment, 1.5 in the second embodiment). The larger the value of L2 / L1 ≧ 1.0, as shown in FIGS. 4A to 4B, the more likely the region 7c adjacent to the steam discharge portion 7 is to bulge due to the internal pressure caused by the steam from the content F. As a result, the peeling force generated with the increase in the internal pressure of the package 1 is likely to be concentrated at the tip A of the steam discharge portion 7, and the peeling at the steam discharge portion 7 becomes even easier. L2 / L1 is, for example, 1.0 to 3.0, preferably 1.1 to 1.8, and more preferably 1.2 to 1.6. Specifically, this value is, for example, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.5, 3.0, and may be within the range between any two of the numerical values exemplified here or any of them or more.

[0017] As shown in Fig. 3, the angle formed by the line segment S1 connecting the tip A and the base 7a and the line segment S2 connecting the base 7a and the point B is preferably 91 - 120 degrees (102 degrees in this embodiment and 96 degrees in the second embodiment). In this case, the peeling force generated with the increase in the internal pressure of the package 1 is likely to be concentrated at the tip A of the steam discharge part 7, and peeling at the steam discharge part 7 becomes even easier. Specifically, this angle is, for example, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120 degrees, and it may also be within the range between any two of the values exemplified here.

[0018] The angle (90 degrees in this embodiment and 73 degrees in the second embodiment) between the pair of line segments S1 connecting the tip A and the base 7a is preferably 60 - 120 degrees, and more preferably 80 - 110 degrees. Specifically, this angle is, for example, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120 degrees, and it may also be within the range between any two of the values exemplified here.

[0019] It is preferable that the part 7b between the tip A and the base 7a of the steam discharge part 7 is curved so as to protrude toward the outer edge 7d side of the steam discharge part 7. In this case, in the vicinity of the tip A, the interval between the pair of parts 7b narrows and the interval between the pair of bases 7a widens, so that peeling at the steam discharge part 7 in the vicinity of the tip A becomes even easier and the steam discharge path after peeling becomes wider. [[ID=拾]]

[0020] The tip A of the steam discharge part 7 is preferably pointed. In this case, peeling at the tip A becomes even easier.

[0021] The heat-welded portion 6 preferably includes a transition portion 8 adjacent to the steam discharge portion 7, where the line width gradually narrows toward the steam discharge portion 7. The transition portion 8 is preferably formed by the inner edge of the transition portion 8 approaching the outer edge of the flange portion 5. In this case, the region 7c adjacent to the steam discharge portion 7 becomes wider, making peeling at the steam discharge portion 7 even easier. The transition portion 8 is part of the other portion 6a.

[0022] The maximum angle between the outer and inner edges of the transition portion 8 is, for example, 5 to 30 degrees (12 degrees in this embodiment, and 22 degrees in the second embodiment), and preferably 8 to 15 degrees. Specifically, this maximum value is, for example, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, and 30 degrees, and may be within the range of any two of the values ​​exemplified here.

[0023] The heat-welded portion 6 is preferably provided on the flat surface of the flange portion 5. As will be described later, the container 3 may be made of a material containing paper material such as pulp, but such materials do not have good moldability compared to resin, and it may be difficult to accurately form ribs on the flange portion 5. For this reason, by providing the heat-welded portion 6 on the flat surface of the flange portion 5, it becomes possible to accurately form the heat-welded portion 6 regardless of the material that makes up the container 3.

[0024] It is preferable that the flange portion 5 is provided with a wide portion 5b. The wide portion 5b is a part whose width (the distance between the inner and outer edges of the flange portion 5) is wider than the average value of the entire flange portion 5. It is preferable that the steam discharge portion 7 be provided in the wide portion 5b. This makes it possible to provide the steam discharge portion 7 without widening the entire flange portion 5 to match the steam discharge portion 7 or causing the inner edge of the flange portion 5 to protrude inward into the container 3. Furthermore, it is preferable that the outer edge of the flange portion 5 be rectangular in shape, even if the corners are chamfered when viewed from above, and it is preferable that the wide portion 5b be provided in the corner of the rectangle. Note that "view from above" means viewing the microwave packaging 1 from vertically above.

[0025] The material of container 3 is not particularly limited and can be, for example, a resin (e.g., polyolefin, more specifically, polypropylene) or a material containing paper material such as pulp. In one example, container 3 comprises a paper material layer and a resin layer bonded to the paper material layer. The resin layer can be made of any resin that can be heat-welded to the lid 2, and can be made of polyolefin resins such as polyethylene, polypropylene, ethylene-vinyl acetate copolymer, or ethylene-propylene block copolymer. The paper material layer can be made of paper material such as pulp. The resin layer can be bonded to the paper material layer with an adhesive.

[0026] The lid portion 2 is preferably made of a film having an outer edge that is approximately the same size as the outer edge of the flange portion 5. The lid portion 2 preferably comprises a base layer and a sealant layer. The lid portion 2 is preferably heat-shrinkable. In one example, the lid portion 2 can be made heat-shrinkable by making the base layer of a shrink film (heat-shrinkable film). After steam is released from the steam discharge portion 7, if the lid portion 2 and the flange portion 5 are in close contact at the steam discharge portion 7, the inside of the packaged body 1 may become depressurized when the packaged body 1 cools down. However, if the lid portion 2 is heat-shrinkable, the lid portion 2 will shrink, making it difficult for the lid portion 2 and the flange portion 5 to adhere to each other. In addition, the shrinkage force of the lid portion 2 can bend the flange portion 5, thereby suppressing adhesion between the lid portion 2 and the flange portion 5.

[0027] Shrink film is a resin film that has heat-shrinkable properties achieved by, for example, stretching (uniaxial stretching or biaxial stretching). Suitable materials include polyester resins such as polyethylene terephthalate, polyamide resins such as nylon 6, and olefin resins such as polyethylene and polypropylene. The lid portion 2 may also have an outer layer, such as a printed layer, laminated on the outside of the base material layer.

[0028] The sealant layer can be formed from a polyolefin resin such as polyethylene, polypropylene, ethylene-vinyl acetate copolymer, or ethylene-propylene block copolymer, and more specifically, unstretched polypropylene or linear low-density polyethylene can be used. More preferably, an easy-peel sealant may be made by mixing polyethylene and polypropylene in a predetermined ratio. This makes it easy to peel the lid portion 2 from the flange portion 5.

[0029] Here, it is also possible to adjust the peel strength by changing the ratio of the resins to be mixed. For example, if the container body 4 is made of polypropylene, increasing the proportion of polypropylene in the mixed resin will increase the adhesive strength, while decreasing it will improve the peelability.

[0030] 1-2. Manufacturing method of microwave oven packaging 1 As shown in Figure 5, the microwaveable packaging 1 can be manufactured by filling the container 3 with contents F, placing the lid 2 on the flange 5, and then pressing the seal bar 9 against the lid 2 to form a heat-sealed portion 6.

[0031] As shown in Figure 6, the seal bar 9 is provided with a projection 9a that corresponds to the shape of the heat-welded portion 6, and by pressing the heated projection 9a against the lid portion 2, the lid portion 2 and the flange portion 5 can be heat-welded together.

[0032] 2. Second Embodiment A second embodiment of the present invention will be described with reference to Figure 7. This embodiment differs from the first embodiment in the shape of the heat-welded portion 6.

[0033] In the first embodiment, the angle between the pair of line segments S1 connecting the tip A and the base 7a is larger than in the second embodiment. Therefore, in the first embodiment, steam can be discharged more smoothly than in the second embodiment.

[0034] Furthermore, in the second embodiment, the portion 7b between the tip A and the base 7a is straight, whereas in the first embodiment, the portion 7b is curved so as to be convex toward the outer edge 7d of the steam discharge portion 7. For this reason, in the first embodiment, peeling at the steam discharge portion 7 near the tip A is easier than in the second embodiment.

[0035] Furthermore, in the first embodiment, the maximum angle between the outer and inner edges of the transition section 8 is smaller than in the second embodiment. As a result, the transition section 8 is provided over a wider area, and consequently, the region 7c adjacent to the steam discharge section 7 is more likely to bulge, making peeling at the steam discharge section 7 even easier. [Explanation of Symbols]

[0036] 1: Microwave packaging 2: Lid 3: Container 4: Container body 4a:Top edge 5: Flange section 5a: Common border 5b: Wide part 6: Heat welded part 6a: Part 7: Steam discharge section 7a: Root 7b: Part 7c: area 7d: Outer edge 7e: First line segment 7f: Second line segment 8: Transition Section 9: Silver 9a:Protrusion A: Tip F:Contents S1: Line segment S2: Line segment

Claims

1. A microwave-safe packaging for preserving contents in an airtight state, The container comprises a film-like lid and a container sealed by the lid. The container has a container body formed in a concave shape and capable of containing contents, and an annular flange portion provided so as to extend outward from the upper end of the container body. The flange portion is provided with a heat-welded portion where the flange portion and the cover portion are heat-welded together. The heat-welded portion is provided around the entire circumference of the flange portion. The heat-sealed portion is provided with only one steam discharge port for discharging steam generated when the contents are heated in a microwave oven. The steam discharge section is configured by curving a part of the heat-welded section toward the inner edge of the flange section. The average line width of the steam discharge section is smaller than the average line width of other parts of the heat-welded section. Let L1 be the length of the first line segment connecting the pair of roots on the inner edge side of the steam discharge section, let B be the point where a straight line passing through the tip A of the steam discharge section and parallel to the first line segment reaches the inner edge of the heat-welded section, and let L2 be the length of the second line segment connecting the tip A and point B. Then L2 / L1 ≥ 1.

0. The angle α formed by the line segment connecting the tip A and the base and the line segment connecting the base and point B is between 91 and 120 degrees. A packaging body in which the angle β between a pair of line segments S1 connecting the tip A and each of the pair of bases is 60 to 100 degrees.

2. The packaging according to claim 1, The angle α is between 91 and 110 degrees. The packaging body has an angle β of 60 to 95 degrees.

3. A packaging body according to claim 1 or claim 2, A packaging body in which the portion between the tip A and the base is curved so as to be convex toward the outer edge of the steam discharge portion.

4. A packaging according to any one of claims 1 to 3, The aforementioned tip A is a pointed packaging body.

5. A packaging according to any one of claims 1 to 4, The heat-sealed portion is provided with a transition portion adjacent to the steam discharge portion, where the line width gradually narrows toward the steam discharge portion, and the transition portion extends to the base, in the packaging body.

6. A packaging body according to any one of claims 1 to 5, The heat-sealed portion is provided on the flat surface of the flange portion, and is part of the packaging body.

7. A packaging body according to any one of claims 1 to 6, The container is a packaging body comprising a paper material layer and a resin layer bonded to the paper material layer.

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