STEAM-RELEASING FLAT POUCH

Abstract

The steam-releasing flat pouch comprises a seal part, a steam-releasing seal part, and a steam discharge part. The seal part seals stacked sheets. The steam-releasing seal part is located in the inner parts of the sheet inside the seal part, and is configured to join parts of the sheet so that they are not continuous with the seal part. The steam discharge part is formed in the steam-releasing seal part and configured not to allow communication with the outside when the steam-releasing seal part is not peeled, and to allow communication with the outside when the steam-releasing seal part is peeled. The steam-releasing seal part includes an anterior peeling part including a part that peels apart first as the pressure increases, and a posterior peeling part including a part that peels apart last. The width of the posterior peeling part is smaller than the width of the anterior peeling part.

Description

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a continuation application filed under 35 U.S.C. § 111(a) claiming the benefit under 35 U.S.C. §§ 120 and 365(c) of International Patent Application No. PCT/JP2018/029745, filed on Aug. 8, 2018, which is based upon and claims the benefit of priority to Japanese Patent Application No. 2017-157175, filed on Aug. 16, 2017; the disclosures of which are all incorporated herein by reference in their entireties.

TECHNICAL FIELD

The present invention relates to a steam-releasing flat pouch.

BACKGROUND

A steam-releasing flat pouch which discharges water vapor, generated from its contents by heating the contents, to the outside is known. PTL 1 discloses an example of a conventional steam-releasing pouch. As shown in FIG. 11, the steam-releasing flat pouch (100) of PTL 1 comprises a laminate (150) that forms an storage space (110) in which the contents are stored, and a heat-welded part (120) where the laminate (150) is joined so that the storage space (110) is closed. The heat-welded part (120) includes an outer peripheral part (121) corresponding to the outer shape of the steam-releasing flat pouch (100), and a protruded part (130) formed so as to protrude from the outer peripheral part (121) toward the storage space (110). At a portion surrounded by the outer peripheral part (121) and the protruded part (130), a notch (140) is formed which communicates the outside of the steam-releasing flat pouch (100) in a state where the storage space (110) is closed by the heat-welded part (120). In a state where the protruded part (130) is joined with the laminate (150), since the space between the storage space (110) and the notch (140) is closed by the protruded part (130), the contents in the storage space (110) do not move to the notch (140).

When the steam-releasing flat pouch (100) is heated by a heating means such as a microwave oven, the pressure in the storage space (110) is increased by the water vapor generated from the contents, and a force is exerted on the protruded part (130) that causes the protruded part (130), more specifically, the upper laminate (151) and the lower laminate (152) constituting the protruded part (130) to peel apart. When the pressure in the storage space (110) rises to a certain level, a part of the protruded part (130) peels apart as shown in FIG. 12, and the peeling of the protruded part (130) proceeds towards the outer peripheral part (121) of the heat-welded part (120). As shown in FIG. 13, when the peeling of the protruded part (130) reaches the notch (140), the storage space (110) and the outside of the steam-releasing flat pouch (100) are communicated via the notch (140), and the water vapor in the storage space (110) is discharged to the outside through the notch (140).

• [Citation List] [Patent Literature] [PTL 1]JP H11208739 A

SUMMARY OF THE INVENTION

Technical Problem

According to the above-described steam releasing flat pouch (100), in the state where the storage space (110) and the outside of the steam-releasing flat pouch (100) communicate with each other through the notch (140), the upper laminate (151) and the lower laminate (152) are communicated with each other at the heat-welded part (120) which is a part of the portion of the laminate (150) where the notch (140) is formed. Thus, when the distance between the notch (140) and the contents is short and water vapor is being discharged from the notch (140), the contents may leak from the notch (140) together with the water vapor.

Solution to Problem

(1) A steam-releasing flat pouch according to the present invention comprises, a seal part configured to seal stacked sheets so as to form an storage space for storing contents, a steam-releasing seal part joining parts of the sheets respectively located in inner parts of the sheets so that the joined parts are not continuous with the seal part, each inner part being a part of the corresponding sheet inside the seal part, and a steam discharge part formed in the steam-releasing seal part and configured not to allow the storage space to communicate with the outside when the steam-releasing seal part is not peeled apart, and to allow the storage space to communicate with the outside when the steam-releasing seal part is peeled apart, wherein the steam-releasing seal part includes an anterior peeling part including a part that peels apart first in the steam-releasing seal part as a pressure in the storage space increases, and a posterior peeling part including a part that peels apart last in the steam-releasing seal part, and, a width of the posterior peeling part in a direction different from a direction in which peeling of the steam-releasing seal part proceeds is smaller than a width of the anterior peeling part in the direction different from the direction in which the peeling proceeds.

When the steam-releasing flat pouch whose storage space is closed by the seal part is heated by the heating means, in an example, the pouch is set such that one of the stacked sheets is positioned below, and the other of the stacked sheets provided with the steam discharge part is positioned above. In this state, when the steam-releasing flat pouch is heated, the pressure in the storage space is increased by the steam generated from the contents, and a force for causing the steam-releasing seal part to peel apart is applied to the steam-releasing seal part. Once the pressure in the storage space rises to a certain level, peeling of the steam-releasing seal part starts from the anterior peeling part and the peeling of the steam-releasing seal part proceeds toward the posterior peeling part. When the peeling of the steam-releasing seal part reaches the steam discharge part, the steam discharge part allows the storage space to communicate with the outside. Therefore, the steam in the storage space is discharged to the outside through the steam discharge part. Thus, the increase in pressure in the storage space is suppressed, and the force for causing the steam-releasing seal part to peel apart is reduced. However, since the width of the posterior peeling part is smaller than the width of the anterior peeling part, a situation where the peeling of the steam-releasing seal part stops before the end of the posterior peeling part is unlikely to occur. When the peeling of the steam-releasing seal part reaches the end of the posterior peeling part, the portion of the sheet on top that has been joined by the steam-releasing seal part moves upward so as to be separated from the sheet below and the contents. In the above-described steam-releasing flat pouch, the steam-releasing seal part is formed in the inner part, and the steam discharge part is formed in the steam-releasing seal part. Thus, when the sheet on top moves upward, the steam discharge part also moves upward so as to be separated from the sheet below and the contents. Thus, the contents are unlikely to leak when the steam is discharged.

(2) According to a preferable example, in the steam-releasing flat pouch according to (1), the posterior peeling part is formed so that the width thereof becomes narrower toward the direction in which the peeling proceeds.

Thus, when the force which causes the steam-releasing seal part to peel apart is applied to the steam-releasing seal part, local stress concentration is unlikely to occur in the steam-releasing seal part.

(3) According to a preferable example, in the steam-releasing flat pouch according to (1) or (2), the steam discharge part includes a cut or an aperture penetrating one of the stacked sheets, and is formed so as to extend in the direction in which the peeling proceeds.

In a state where the peeling of the steam-releasing seal part has not reached the aperture or cut of the steam discharge part, the aperture or cut does not allow the storage space to communicate with the outside. In a state where the peeling of the steam-releasing seal part has reached the aperture or cut, the aperture or cut allows the storage space to communicate with the outside, and the area (hereinafter referred to as communication area) of the aperture or cut that directly communicates between the storage space with the outside increases as the peeling progresses. Since the above-described steam-releasing flat pouch is formed so that the aperture or cut extends in the peeling progress direction, the communication area gradually increases as the peeling proceeds. Thus, the flow rate of the steam discharged outside from the storage space does not increase rapidly, and it helps the peeling of the steam-releasing seal part to reach the end of the posterior peeling part.

(4) According to a preferable example, in the steam-releasing flat pouch according to any one of (1) to (3), the pouch further comprises a guide part constituting a guide for separating the sheets and a part of the seal part in order to open the storage space closed by the seal part, and the steam-releasing seal part is provided in parts of the sheets that are separated by the guide part.

Thus, when the portions of the sheets to be separated (hereinafter referred to as separable part) by the guide part are separated, the steam discharge part does not remain in the portions of the sheets that store the contents, and the contents do not leak from the steam discharge part when contents are extracted from the storage space.

(5) According to a preferable example, in the steam-releasing flat pouch according to any one of (1) to (4), a dimension of the steam discharge part in the direction in which the peeling proceeds is 12.5% or larger of a dimension of the steam-releasing seal part in the direction in which the peeling proceeds.

If the dimension of the steam discharge part is within the above range, steam is appropriately discharged from the steam discharge part when the storage space communicates with the outside through the steam discharge part.

(6) In a preferable example, in the steam-releasing flat pouch according to any one of (1) to (5), a dimension of the steam discharge part in the direction in which the peeling proceeds is 62.5% or smaller of a dimension of the steam-releasing seal part in the direction in which the peeling proceeds.

If the dimension of the steam discharge part is within the above range, foreign substance is unlikely to enter the steam discharge part.

(7) According to a preferable example, in the steam-releasing flat pouch according to any one of (1) to (6), the pouch further comprises the contents contained in the storage space.

Advantageous Effects of Invention

According to the steam-releasing flat pouch of the present invention, the contents are unlikely to leak when steam is discharged.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a steam-releasing flat pouch according to an embodiment of the present invention.

FIG. 2 is an enlarged view of the steam-releasing seal part in FIG. 1 and its surroundings.

FIG. 3 is a front view of a steam-releasing flat pouch before an opening thereof is closed.

FIG. 4 is a front view of a steam-releasing flat pouch in a state where a part of the steam-releasing seal part in FIG. 1 is peeled.

FIG. 5 is a front view of a steam-releasing flat pouch in a state where the steam-releasing seal part in FIG. 4 is completely peeled.

FIG. 6 is a cross-sectional view taken along the line D6-D6 of FIG. 5.

FIG. 7 is a table showing test conditions of Comparative Examples and Examples regarding tests.

FIG. 8 is a table showing test results of Comparative Examples and Examples.

FIG. 9 is an enlarged view of the steam-releasing seal part and its surroundings according to a modification.

FIG. 10 is an enlarged view of the steam-releasing seal part and its surroundings according to a modification.

FIG. 11 is a front view of a conventional steam-releasing flat pouch.

FIG. 12 is a cross-sectional view taken along the line D12-D12 of FIG. 11.

FIG. 13 is a cross-sectional view showing a state where the protruded part of FIG. 12 is peeled.

DETAILED DESCRIPTION

With reference to the accompanying Figures, a description will now be given of representative embodiments according to the present invention. The present invention is not limited to the following representative embodiments, and appropriate modifications can be made without departing from the spirit of the present invention. The representative embodiments described below are merely examples of the present invention, and the design thereof could be appropriately changed by one skilled in the art. Here, the drawings are schematic, and the relationship between thickness and plane size, the ratio of the thickness of each layer, etc., may be different from actual ones. The embodiments described below are merely examples of the configurations for embodying the technical idea of the present invention, and the technical idea of the present invention should not limit the materials, shapes, structures, and the like of the components to those described below. The technical idea of the present invention can be modified in various ways within the technical scope specified by the claims.

The same constituent elements are denoted by the same reference numerals unless there is a reason for the sake of convenience, and redundant description is omitted. In the drawings referred to in the following description, for clarity, characteristic parts are enlarged, and thus the components are not shown to scale. It is, however, clear that one or more embodiments can be implemented without such details. In addition, known structures and devices may be schematically represented for simplicity.

Embodiments

FIG. 1 shows an example of a steam-releasing flat pouch 10 that can store contents C suitable for heating and can discharge the water vapor generated at the contents C. The contents C generate water vapor when they are heated. An example of the contents C is food. An example is food cooked by heating. For example, the food may be ingredients of beef bowl, a hamburger steak, or stew. The steam-releasing flat pouch 10 is configured to store the contents C for a long period maintaining their quality.

The steam-releasing flat pouch 10 includes a sheet 20, a seal part 30, an opening 40 (see FIG. 3), a guide part 50, a steam-releasing seal part 60, and a steam discharging part 70. The dots in FIG. 1 and other drawings represent the seal part 30 and the steam-releasing seal part 60. The sheet 20 include a first sheet 21 and a second sheet 22. The first sheet 21 and the second sheet 22 are facing each other so as to form a storage space 10C between the sheets 21 and 22 for storing the contents C. The configuration of the sheet 20 can be optionally selected. In a first example, the sheets 21 and 22 are two sheets formed individually. In a second example, the facing sheets 21 and 22 are formed by folding a single sheet.

The sheet 20 (the sheets 21 and 22) has a layered structure in which a plurality of layers are laminated. The layered structure of the sheet 20 (the sheets 21 and 22) can be optionally selected. In the first example, the sheets 21 and 22 have the same layered structure. In the second example, the first and second sheets 21 and 22 have different layered structures. FIG. 1 shows a steam-releasing flat pouch 10 constituted by a sheet 20 having the layer structure of the first example.

Each of the sheets 21 and 22 includes an outermost layer, an intermediate layer, and an innermost layer. An example of a method for manufacturing the sheets 21 and 22 is dry lamination. The outermost layer mainly excels in gloss, printing suitability, and retort resistance. Retort resistance means resistance to retort processing. An example of the material forming the outermost layer is a transparent material. An example of a transparent material is polyethylene terephthalate. The intermediate layer mainly excels in retort resistance, moisture resistance, and gas barrier properties. The intermediate layer includes a printed layer, a first adhesive layer, an oriented nylon layer, and a second adhesive layer. The printed layer is placed on the inner side of the outermost layer. In one example, the printed layer is formed with patterns, texts such as item description, and the like printed on the outer surface thereof. The first adhesive layer is placed on the inner side of the printed layer. The oriented nylon layer is formed on the inner side of the first adhesive layer. The second adhesive layer is formed on the inner side of the oriented nylon layer. An example of the material forming each adhesive layer is a dry laminate adhesive. The innermost layer excels in retort resistance, heat sealability, and impact resistance. The innermost layer is placed on the inner side of the second adhesive layer. An example of the material configuring the innermost layer is non-oriented polypropylene.

The seal part 30 joins the sheets 21 and 22 so that the sheets 21 and 22 are not separated. In one example, the seal part 30 joins the innermost layer of the first sheet 21 and the innermost layer of the second sheet 22. An example of the method for forming the seal part 30 is heat sealing. The outer shape of the steam-releasing flat pouch 10 in front view can be optionally selected. In the example shown in FIG. 1, the outer shape of the steam-releasing flat pouch 10 is a rectangle. The sheet 20 can be divided into a portion surrounded by the seal part 30 (hereinafter referred to as inner part 23) and the seal part 30. The storage space 10C is a space surrounded by the inner part 23 of the first sheet 21 and the inner part 23 of the second sheet 22, and is closed by the seal part 30 so as not to communicate with the outside of the steam-releasing flat pouch 10.

The seal part 30 joins the first sheet 21 and the second sheet 22 so that the storage space 10C is closed. The seal part 30 is divided into first to fourth seal parts 31 to 34. The first seal part 31 is formed along the first side 20A of the sheet 20. The second seal part 32 is formed along the second side 20B of the sheet 20. The third seal part 33 is formed along the third side 20C of the sheet 20. The fourth seal part 34 is formed along the fourth side 20D of the sheet 20. The first seal part 31, the third seal part 33, and the fourth seal part 34 are formed ahead of the second seal part 32 in order to store the contents in the storage space 10C. In a state where the first seal part 31, the third seal part 33, and the fourth seal part 34 are formed but the second seal part 32 is not formed, an opening 40 for putting the contents into the storage space 10C (see FIG. 3) is formed in the steam-releasing flat pouch 10. The second seal part 32 is formed after the contents are put into the storage space 10C, and then the opening 40 is closed by the second seal part 32. In the following, the direction along the first side 20A and the second side 20B in the front view of the steam-releasing flat pouch 10 is referred to as a first direction, and the direction along the third side 20C and the fourth side 20D is referred to as a second direction.

An inner edge 31A which is an edge of the first seal part 31 on the inner part 23 side, an inner edge 32A which is an edge of the second seal part 32 on the inner part 23 side, an inner edge 33A which is an edge of the third seal part 33 on the inner part 23 side, and an inner edge 34A which is an edge of the fourth seal part 34 on the inner part 23 side define the outer shape of the inner part 23. An outer edge 31B which is the edge of the first seal part 31 opposite to the inner edge 31A, an outer edge 32B which is the edge of the second seal part 32 opposite to the inner edge 32A, an outer edge 33B which is the edge of the third seal part 33 opposite to the inner edge 33A, and an outer edge 34B which is the edge of the fourth seal part 34 opposite to the inner edge 34A define the outer shape of the steam-releasing flat pouch 10.

The width of each of the seal parts 31 to 34 can be optionally selected. The width of each seal part 31 to 34 is the distance between the inner edges 31A to 34A and the outer edges 31B to 34B along a normal line of the center line in each seal part 31 to 34. The center line of each seal part 31 to 34 is an imaginary line segment passing between the inner edges 31A to 34A and the outer edges 31B to 34B. When the width of each of the seal parts 31 to 34 vary for each portion, for example, the maximum width or the average widths of the plurality of portions in each of the seal parts 31 to 34 represents the width of respective seal part.

Preferably, the dimension in the first direction and the dimension in the second direction of the steam-releasing flat pouch 10 are determined, for example, from the relationship between the amount of contents C to be stored and the ease of carrying the steam-releasing flat pouch 10. The dimension in the first direction of the steam-releasing flat pouch 10 is the length of a line segment orthogonal to the second direction between the outer edge 33B of the third seal part 33 and the outer edge 34B of the fourth seal part 34. When the dimension of the steam-releasing flat pouch 10 in the first direction differ for each portion, for example, the maximum dimension or the average dimension of the plurality of portions represents the dimension of the steam-releasing flat pouch 10 in the first direction. In one example, the dimension of the steam-releasing flat pouch 10 in the first direction is 130 mm. The dimension in the second direction of the steam-releasing flat pouch 10 is the length of a line segment orthogonal to the first direction between the outer edge 31B of the first seal part 31 and the outer edge 32B of the second seal part 32. When the dimension of the steam-releasing flat pouch 10 in the second direction differs for each portion, for example, the maximum dimension or the average dimension of the plurality of portions represents the dimension of the steam-releasing flat pouch 10 in the second direction. In one example, the dimension of the steam-releasing flat pouch 10 in the second direction is 135 mm.

The opening 40 (see FIG. 3) is formed between a lower part 21A of the first sheet 21 and a lower part 22A of the second sheet 22 so that the contents C can be filled into the storage space 10C. In the steam-releasing flat pouch 10 shown in FIG. 1, the opening 40 is closed by the second seal part 32. The steam-releasing flat pouch 10 of the opening 40 being closed (hereinafter referred to as closed steam-releasing flat pouch 10) includes a pouch body 10A and a separable part 10B. The pouch body 10A and the separable part 10B are segmented by a perforated line 51 constituting a guide part 50. The pouch body 10A is a part for storing the contents C. The separable part 10B is a part of each of the sheets 21 and 22 including the first seal part 31, and it is a part that the user separates from the pouch body 10A in order to extract the contents C from the storage space 10C.

The guide part 50 is formed between the pouch body 10A and the separable part 10B so that each of the sheets 21 and 22 is easily cut when the separable part 10B is separated from the pouch body 10A. The guide part 50 includes a perforated line 51 and a notch 52. The perforated line 51 is a group of perforations formed in the seal parts 33 and 34 and the inner part 23 of the sheets 21 and 22, and is formed as a straight line. The notch 52 is formed in at least one of the third seal part 33 or the fourth seal part 34 such that the tip of the notch 52 is located on an imaginary line obtained by extending the perforated line 51. FIG. 1 shows an example where the notch 52 is formed in both of the third seal part 33 and the fourth seal part 34.

The steam-releasing flat pouch 10 is heated by heating means (heating device) in order to heat the contents C. An example of the heating means is a microwave oven. Steam is generated from the contents C as the steam-releasing flat pouch 10 is heated. Because the storage space 10C of the closed steam-releasing flat pouch 10 is closed by the seal part 30, the pressure in the storage space 10C increases as steam is generated.

In the inner part 23, a steam-releasing seal part 60 is a part where the innermost layer of the first sheet 21 and the innermost layer of the second sheet 22 are joined, and it is configured such that, as the pressure in the storage space 10C increases, peeling apart of the innermost layer of the first sheet 21 and the innermost layer of the second sheet 22 occur. In the following, the phrase “the steam-releasing seal part 60 peels apart” means that the innermost layer of the first sheet 21 and the innermost layer of the second sheet 22 both constituting the steam-releasing seal part 60 peel apart from each other. In a preferred example, the steam-releasing seal part 60 is configured to be peeled apart when the pressure in the storage space 10C rises to a predetermined pressure. A steam discharge part 70 allows the storage space 10C to communicate with the outside of the steam-releasing flat pouch 10 when the steam-releasing seal part 60 peels apart so as to discharge steam generated at the contents C to the outside of the steam-releasing flat pouch 10. By discharging the steam from the steam discharge part 70, the increase in the pressure of the storage space 10C is suppressed, and rupture of the steam-releasing flat pouch 10 is avoided. The steam discharge part 70 is provided in the inside of the outer shape of the steam-releasing seal part 60.

The steam-releasing seal part 60 is provided so as not to be continuous with the seal part 30. Since the steam-releasing seal part 60 is separated from the seal part 30, the steam discharge part 70 is formed at a distance from the seal part 30 in the sheet 20. There may be one or more steam-releasing seal parts 60 provided in the inner part 23. The steam-releasing seal part 60 is provided at any suitable location in the inner part 23. In a preferred example, the steam-releasing seal part 60 is provided at a place where high stress concentration occurs when the pressure in the storage space 10C increases. In a first example, the steam-releasing seal part 60 is provided in the separable part 10B at a position facing the center of the first seal part 31 in the longitudinal direction. In the first example, when the separable part 10B is separated from the pouch body 10A, the steam-releasing seal part 60 does not remain in the pouch body 10A, and thus the contents C would not leak from the steam discharge part 70 when the contents C are removed from the storage space 10C. In a second example, the steam-releasing seal part 60 is provided in the pouch body 10A.

FIG. 2 is an enlarged view of the steam-releasing seal part 60 and its surroundings. The outer shape of the steam-releasing seal part 60 may take various shapes. Examples include a triangle, a shape similar to a triangle, a trapezoid, a shape similar to a trapezoid, and a convex shape. In the example shown in the figure, the outer shape of the steam-releasing seal part 60 is an isosceles triangle. The sides constituting the isosceles triangle are a first side 60A and a second side 60B, both having equal sides, and a third side 60C which is the bottom side. In the first direction, the seal width XA of the steam-releasing seal part 60 is the distance between the first side 60A and the second side 60B.

When the pressure in the storage space 10C increases due to heating of the steam-releasing flat pouch 10, the steam-releasing seal part 60 peels apart, and the peeling of the steam-releasing seal part 60 proceeds as the pressure increases. When the peeling of the steam-releasing seal part 60 reaches the steam discharge part 70, the storage space 10C and the outside of the steam-releasing flat pouch 10 communicate with each other via the steam discharge part 70. The area of the steam discharge part 70 directly communicating with the storage space 10C, that is, the communication area of the steam discharge part 70 becomes greater as the peeling of the steam-releasing seal part 60 proceeds. Assuming that the pressure in the storage space 10C is constant, the flow rate of steam discharged to the outside of the steam-releasing flat pouch 10 through the steam discharge part 70 increases as the communication area of the steam discharge part 70 increases. The communication area is zero in a state where the steam-releasing seal part 60 does not peel apart, and in a state where the peeling of the steam-releasing seal part 60 has not reached the steam discharge part 70. When the steam-releasing seal part 60 surrounding the steam discharge part 70 entirely peels apart, the communication area becomes the largest.

The steam-releasing seal part 60 includes an anterior peeling part 61 including a part that peels apart first in the steam-releasing seal part 60 and a posterior peeling part 62 including a part that peels apart last in the steam-releasing seal part 60. In the example shown in the figure, the portion of the steam-releasing seal part 60 that peels apart first is a part or all of the third side 60C. The portion of the steam-releasing seal part 60 that peels apart last is the apex 60D. The seal width XA of the posterior peeling part 62 in a direction different from the direction in which the peeling of the steam-releasing seal part 60 proceeds is smaller than the seal width XA of the anterior peeling part 61 in a direction different from the direction in which the peeling of the steam-releasing seal part 60 proceeds. An example of the “different direction” is a crossing direction, and a preferred example is the direction orthogonal to the other direction.

The anterior peeling part 61 includes, for example, the following parts of the steam-releasing seal part 60. In a first example, the anterior peeling part 61 includes the portion of the steam-releasing seal part 60 extending from the third side 60C to the steam discharge part 70. In the first example, the anterior peeling part 61 does not include the end of the steam discharge part 70 on the side of the storage space 10C (hereinafter referred to as inner end of the steam discharge part 70). When the range of the anterior peeling part 61 is defined as in the first example, the steam discharge part 70 does not communicate with the storage space 10C until peeling of the steam-releasing seal part 60 reaches the posterior peeling part 62. Because the communication area is relatively small in a state immediately after the peeling of the steam-releasing seal part 60 has reached the steam discharge part 70, the force acting to peel the steam-releasing seal part 60 is high. Therefore, the peeling of the posterior peeling part 62 proceeds smoothly following the peeling of the anterior peeling part 61. In a second example, the anterior peeling part 61 includes the portion from the third side 60C to the inner end of the steam discharge part 70. In the second example, the anterior peeling part 61 includes the inner end of the steam discharge part 70. If the range of the anterior peeling part 61 is the range defined in the second example, the inner end of the steam discharge part 70 is directly communicated with the storage space 10C when the anterior peeling part 61 has entirely peeled apart, but because the communication area of the steam discharge part 70 is relatively small, a state where the pressure in the storage space 10C is relatively high is maintained. Thus, the force acting to peel the steam-releasing seal part 60 is high, the peeling of the posterior peeling part 62 proceeds smoothly following the peeling of the anterior peeling part 61.

The steam discharge part 70 can take various configurations. According to the first example, the steam discharge part 70 is a cut or an aperture penetrating the first sheet 21. According to the second example, the steam discharge part 70 is a cut or a hole not penetrating the first sheet 21. The depth of the cut or hole in the second example is preferably such a depth that causes the portion of the first sheet 21 corresponding to the steam discharge part 70 to rupture when the steam-releasing seal part 60 peels apart. The steam discharge part 70 can take various outer shapes. According to the first example, the outer shape of the steam discharge part 70 is a rectangle extending in the first direction or the second direction. According to the second example, the outer shape of the steam discharge part 70 is a regular triangle, an isosceles triangle, a square, or a pentagon or a polygon with more sides. In a state where the peeling of the steam-releasing seal part 60 has not reached the aperture or cut of the steam discharge part 70, the aperture or cut does not allow the storage space 10C to communicate with the outside. In a state where the peeling of the steam-releasing seal part 60 has reached the aperture or cut, the aperture or cut allows the storage space 10C to communicate with the outside, and a communication area which is the area of the aperture or cut that communicates between the storage space 10C with the outside increases as the peeling progresses.

In the first example or the second example, when the outer shape of the steam discharge part 70 is formed so as to extend in the direction in which the peeling of the steam-releasing seal part 60 proceeds (hereinafter referred to as peeling progress direction), the communication area gradually increases in accordance with the progress of the peeling. Thus, the flow rate of the steam discharged outside from the storage space 10C does not increase rapidly, and it helps the peeling of the steam-releasing seal part 60 to reach the apex 60D which is an edge of the posterior peeling part 62.

The ratio of the dimension HB of the steam discharge part 70 in the peeling progress direction to the dimension HA of the steam-releasing seal part 60 in the peeling progress direction (hereinafter referred to as discharge part ratio RA) is preferably determined based on the relationship between the ease of steam discharge and the difficulty of foreign substance entering the steam discharge part 70. The formula for obtaining the discharge part ratio RA is “RA=(HB/HA)×100”. The dimension HA is, for example, the height of the steam-releasing seal part 60 when the outer shape of the steam-releasing seal part 60 is a triangle. The dimension HB is, for example, the long side length of the steam discharge part 70 when the outer shape of the steam discharge part 70 is a rectangle. A preferable example regarding the maximum value of the discharge part ratio RA is 62.5%. A further preferable example regarding the maximum value of the discharge part ratio RA is 25%. When the discharge part ratio RA is 62.5% or less, foreign substance is less likely to enter into the steam discharge part 70. When the discharge part ratio RA is 25% or less, foreign substance is even less likely to enter into the steam discharge part 70. A preferable example regarding the minimum value of the discharge part ratio RA is 12.5%. A further preferable example regarding the minimum value of the discharge part ratio RA is 25%. When the discharge part ratio RA is 12.5% or greater, the steam is appropriately discharged from the steam discharge part 70 when the steam-releasing seal part 60 peels apart. When the discharge part ratio RA is 25% or greater, the steam is further appropriately discharged from the steam discharge part 70 when the steam-releasing seal part 60 peels apart.

FIG. 3 shows the steam-releasing flat pouch 10 of before the opening 40 is closed (hereinafter referred to as unclosed steam-releasing flat pouch 10). The contents C (see FIG. 1) is put into the storage space 10C from the opening 40 of the unclosed steam-releasing flat pouch 10. After putting the contents C into the accommodation space 10C, heat sealing is applied to a sealing-planned part 80 where the second seal part 32 is planned to be formed, and thus the second seal part 32 is formed, and the closed steam-releasing flat pouch 10 shown in FIG. 1 is obtained.

Referring to FIG. 1, an example of method for using the steam-releasing flat pouch 10 is described.

The closed steam-releasing flat pouch 10 is placed in heating means (not shown) such as a microwave oven such that the second sheet 22 is below the first sheet 21, and then it is heated by the heating means. After the heating is finished, the sheets 21 and 22 are torn from the outer end of the notch 52, and a force is applied to the sheets 21 and 22 so that the tearing of the sheets 21 and 22 proceeds along the perforated line 51. By separating the separable part 10B from the pouch body 10A, the contents C are extracted from the storage space 10C to the outside of the steam-releasing flat pouch 10.

Referring to FIGS. 4 to 6, effects of the steam-releasing flat pouch 10 is described.

When the closed steam-releasing flat pouch 10 is heated by the heating means, in one example, it is set such that the second sheet 22 is positioned below and the first sheet 21 having the steam discharge part 70 is positioned above. In this state, when the closed steam-releasing flat pouch 10 is heated, the pressure in the storage space 10C is increased by the steam generated from the contents C, and a force acting to cause the steam-releasing seal part 60 to peel apart is applied to the steam-releasing seal part 60. Once the pressure in the storage space 10C rises to a certain level, peeling of the steam-releasing seal part 60 starts from the anterior peeling part 61 and the peeling of the steam-releasing seal part 60 proceeds toward the posterior peeling part 62. As shown in FIG. 4, when the peeling of the steam-releasing seal part 60 reaches the steam discharge part 70, the steam discharge part 70 allows the storage space 10C to communicate with the outside, so that the steam in the storage space 10C is discharged to the outside through the steam discharge part 70. Thus, the increase of pressure in the storage space 10C is suppressed, and the force acting to cause the steam-releasing seal part 60 to peel apart is reduced. However, because the seal width XA of the posterior peeling part 62 is smaller than the seal width XA of the anterior peeling part 61, a situation where the peeling of the steam-releasing seal part 60 stops before the end of the posterior peeling part 62 is unlikely to occur. As shown in FIG. 5, when the peeling of the steam-releasing seal part 60 reaches the end of the posterior peeling part 62, as shown in FIG. 6, the portion of the first sheet 21 that was joined by the steam-releasing seal part 60 moves upward so as to be separated from the second sheet 22 and the contents C. In the steam-releasing flat pouch 10, the steam-releasing seal part 60 is formed in the inner part 23, and the steam discharge part 70 is formed in the steam-releasing seal part 60. Thus, when the first sheet 21 moves upward, the steam discharge part 70 also moves upward so as to be separated from the second sheet 22 and the contents C. Thus, the contents C are unlikely to leak when the steam is discharged.

(Examples)

The inventor of the present invention performed tests to confirm the relationship between the configuration of the steam-releasing seal part 60 and the steam discharge part 70, and the seal peeling performance and the steam releasing performance, using samples of Examples and Comparative Examples. FIG. 7 shows the test conditions of Comparative Examples and Examples regarding the tests. FIG. 8 shows the test results. In the following, for convenience of explanation, the same reference numerals are given to the parts of the samples of Comparative Examples that are common to the samples of Examples. The samples of Examples are steam-releasing flat pouches 10 according to embodiments. The samples of Comparative Examples are steam-releasing flat pouch 10 provided with structures different from the steam-releasing flat pouches 10 of the Examples. The steam-releasing flat pouch 10 of each Comparative Example differs from the steam-releasing flat pouch 10 of each Example in that the seal width XA of the posterior peeling part 62 in the peeling progress direction is larger than the seal width XA of the anterior peeling part 61 in the peeling progress direction. Apart from this, they have the same configuration as the steam-releasing flat pouches 10 of the Examples.

The specifications regarding the samples of Examples and Comparative Examples are as follows. The material of the outermost layers for the sheets 21 and 22 is polyethylene terephthalate. Each outermost layer has a thickness of 12 ?m. The material of the intermediate layer for each of the sheets 21 and 22 is nylon. The intermediate layer has a thickness of 15 ?m. The material of the innermost layer for each of the sheets 21 and 22 is non-oriented polypropylene. The outermost layer has a thickness of 60 ?m. The dimension of the steam-releasing flat pouch 10 in the first direction is 130 mm. The dimension of the steam-releasing flat pouch 10 in the second direction is 135 mm. One steam-releasing seal part 60 is provided in the inner part 23. The steam-releasing seal part 60 is provided in the separable part 10B at a position facing the center in the longitudinal direction of the first seal part 31.

The steam-releasing seal part 60 has an outer shape of a circle in the samples of Comparative Examples 1 and 5. The circle has a radius of 5 mm. The steam-releasing seal part 60 has an outer shape of square in the samples of Comparative Examples 2 and 6. Each side of the square has a length of 10 mm. The outer shape of the steam-releasing seal part 60 of the samples of Comparative Examples 3 and 7 is a trapezoid configured such that the seal width XA becomes wider from the center of the inner part 23 toward the first seal part 31, that is, in the peeling progress direction. The length of the upper base of the trapezoid is 10 mm, the length of the lower base is 20 mm, and the height is 10 mm. The outer shape of the steam-releasing seal part 60 of the samples of Comparative Examples 4 and 8 is a regular triangle configured such that the seal width XA becomes wider from the center of the inner part 23 toward the first seal part 31, that is, in the peeling progress direction. Each side of the regular triangle has a length of 10 mm.

The outer shape of the steam-releasing seal part 60 of the samples of Examples 1 and 3 is a triangle configured such that the seal width XA becomes narrower from the center of the inner part 23 toward the first seal part 31, that is, in the peeling progress direction. Each side of the regular triangle has a length of 10 mm. The outer shape of the steam-releasing seal part 60 of the samples of Examples 2 and 4 is a trapezoid configured such that the seal width XA becomes narrower from the center of the inner part 23 toward the first seal part 31, that is, in the peeling progress direction. The upper base of the trapezoid has a length of 10 mm, lower base thereof has a length of 20 mm, and the trapezoid has a height of 10 mm.

The first direction of the steam discharge part has a dimension of 1 mm in the samples of Comparative Examples 1 to 4 and the samples of Examples 1 and 2. The second direction of the steam discharge part has a dimension of 3 mm in the samples of Comparative Examples 1 to 4 and the samples of Examples 1 and 2. The first direction of the steam discharge part has a dimension of 3 mm in the samples of Comparative Examples 5 to 8 and the samples of Examples 3 and 4. The second direction of the steam discharge part has a dimension of 1 mm in the samples of Comparative Examples 5 to 8 and the samples of Examples 3 and 4.

In order to evaluate the seal peeling performance, the inventor visually confirmed whether the entire steam-releasing seal part 60 had peeled apart after heating the closed steam-releasing flat pouch 10 using the heating means. The state where the entire steam-releasing seal part 60 has peeled apart is a state where the portions of the first and second sheets 21 and 22 constituting the inner part 23 are not joined. If the entire steam-releasing seal part 60 peels apart, the seal peeling performance is evaluated to be good, and if at least a part of the steam-releasing seal part 60 does not peel apart, the seal peeling performance is evaluated to be not good.

In order to evaluate the steam-releasing performance, the inventor visually confirmed whether the contents C had leaked from the steam discharge part 70 when the closed steam-releasing flat pouch 10 was heated by the heating means to discharge steam from the steam discharge part 70. The state where the contents C do not leak from the steam discharge part 70 is a state where the contents C are not attached to the surface of the first sheet 21 and around the steam-releasing flat pouch 10. The state where the contents C has leaked from the steam discharge part 70 is a state where the contents C are attached to the surface of the first sheet 21 and/or around the steam-releasing flat pouch 10. The test was performed three times. The contents C are ingredients of beef bowl. The ingredients of beef bowl include beef, vegetables, and soup stock. The contents C has a weight of 80 g. The microwave oven has power of 600 W. The heating time of the microwave oven is 1 minute and 20 seconds.

In the section of the seal peeling performance in FIG. 8, the circles indicate a case where the entire steam-releasing seal part 60 peeled apart, and the X indicates a case where at least a part of the steam-releasing seal part 60 did not peel apart. In the section of the steam releasing performance in FIG. 8, the circles indicate a case where the contents C did not leak when the steam was discharged from the steam discharge part 70, and the X indicates a case where the contents C leaked when the steam was discharged from the steam discharge part 70.

According to the steam-releasing flat pouches 10 in Examples, it was confirmed that, when the closed steam-releasing flat pouch 10 is heated by the heating means, the entire steam-releasing seal part 60 peels apart and the contents C are unlikely to leak. In addition, it was confirmed that, when the steam discharge part 70 has a shape extending in the peeling progress direction, the entire steam-releasing seal part 60 peels apart and the contents C are further unlikely to leak.

(Modifications)

The description of the embodiments described above is only an exemplary form of the steam-releasing flat pouch according to the present invention, and it is not intended that forms thereof are limited. The steam-releasing flat pouch according to the present invention could encompass, for example, modifications of the above embodiments and combinations of at least two modifications that are mutually compatible.

The structure of the steam-releasing seal part 60 can be arbitrarily changed. FIG. 9 shows an example of a modification for the steam-releasing seal part 60. The steam-releasing seal part 60 includes an anterior peeling part 61 and a posterior peeling part 62. For example, the outer shape of the anterior peeling part 61 may be a semicircle. The outer shape of the posterior peeling part 62 is an isosceles triangle whose seal width XA decreases in the peeling progress direction. The steam discharge part 70 can be provided at any suitable position inside the outer shape of the steam-releasing seal part 60. According to a first example, the steam discharge part 70 is provided so as to straddle the anterior peeling part 61 and the posterior peeling part 62. According to a second example, the steam discharge part 70 is provided only in the posterior peeling part 62 of the steam-releasing seal part 60.

FIG. 10 shows an example of another modification of the steam-releasing seal part 60. The steam-releasing seal part 60 includes an unsealed part 71 provided so as to surround the steam discharge part 70. The unsealed part 71 is a part inside the outer shape of the steam-releasing seal part 60 where the first sheet 21 and the second sheet 22 are not joined. After forming the steam discharge part 70 in the first sheet 21, if the steam-releasing seal part 60 is formed by joining the first sheet 21 and the second sheet 22 so that the unsealed part 71 is formed, thermal contraction around the steam discharge part 70 in the first sheet 21 is suppressed. This facilitates the steam discharge part 70 maintaining its defined dimensions.

REFERENCE SIGNS LIST

• • 10 . . . Steam-releasing flat pouch; 10C . . . storage space; 20 . . . Sheet; 23 . . . Inner part; 30 . . . Seal part; 50 . . . Guide part; 60 . . . Steam-releasing seal part; 61 . . . Anterior peeling part; 62 . . . Posterior peeling part; 70 . . . Steam discharge part; C . . . Contents.

Claims

1. A steam-releasing flat pouch comprising:

a seal part configured to seal stacked sheets so as to form a storage space for storing contents;

a steam-releasing seal part joining parts of the sheet respectively located in inner parts of the sheet so that the joined parts are not continuous with the seal part, each inner part being a part of the corresponding sheet inside the seal part; and a steam discharge part formed in the steam-releasing seal part and configured not to allow the storage space to communicate with the outside when the steam-releasing seal part is not peeled apart, and to allow the storage space to communicate with the outside when the steam-releasing seal part is peeled apart, wherein: the steam-releasing seal part includes an anterior peeling part including a part that peels apart first in the steam-releasing seal part as a pressure in the storage space increases, and a posterior peeling part including a part that peels apart last in the steam-releasing seal part; and a width of the posterior peeling part in a direction different from a direction in which peeling of the steam-releasing seal part proceeds is smaller than a width of the anterior peeling part in the direction different from the direction in which the peeling proceeds.

2. The steam-releasing flat pouch of claim 1, wherein:

the posterior peeling part is formed so that the width thereof becomes narrower in the direction in which the peeling proceeds.

3. The steam-releasing flat pouch of claim 1, wherein:

the steam discharge part includes a cut or an aperture penetrating one of the stacked sheets, and is formed so as to extend in the direction in which the peeling proceeds.

4. The steam-releasing flat pouch of claim 1, further comprising:

a guide part constituting a guide for separating the sheet; and

a part of the seal part in order to open the storage space closed by the seal part, wherein: the steam-releasing seal part is provided in parts of the sheet that are separated by the guide part.

5. The steam-releasing flat pouch of claim 1, wherein:

a dimension of the steam discharge part in the direction in which the peeling proceeds is 12.5% or larger of a dimension of the steam-releasing seal part in the direction in which the peeling proceeds.

6. The steam-releasing flat pouch of claim 1, wherein:

a dimension of the steam discharge part in the direction in which the peeling proceeds is 62.5% or smaller of a dimension of the steam-releasing seal part in the direction in which the peeling proceeds.

7. The steam-releasing flat pouch of claim 1, further comprising:

the contents stored in the storage space.