WO2025205819A1 - Packaging bag - Google Patents

Abstract

The present invention provides a packaging bag for microwave ovens whereby steam generated when heating the contents of said bag can be vented reliably and suitably by means of a simple configuration, without having to provide flaps formed in a pressed-palms shape (pressed-palms section).　According to the present invention, there is provided a packaging bag comprising, in the peripheral surface thereof, first and second surfaces that face each other, an opening that is open upward, and an opening/closing member configured to open/close the opening, wherein the opening/closing member has a first engaging member and a second engaging member, and defining an upper region and a lower region to be regions where the second engaging member faces the second surface, the upper region has a portion where the seal strength per unit width between the second engaging member and the second surface is relatively small, and in a region of the lower region that overlaps said portion in the vertical direction, the second engaging member and the second surface are not heat-sealed, or are heat-sealed to a lower seal strength per unit width than said portion.

Description

packaging bag

The present invention relates to a self-standing packaging bag for microwave ovens, made from flexible film formed into a bag shape.

Patent Document 1 discloses a packaging bag for use in a microwave oven that has an openable and closable latch.

JP 2016-137929 A

The packaging bag in Patent Document 1 makes it possible to heat any content by opening the joint and placing the content to be heated inside the packaging bag. In the configuration of Patent Document 1, steam generated when the contents are heated is released to the outside through a steam release seal provided on the folded flap (folded portion).

However, some bag making machines do not have the functionality to provide folded flaps (gable portions) on packaging bags. For this reason, there is a demand for a simple mechanism for venting steam generated when contents are heated in microwave packaging bags, without providing folded flaps (gable portions). Even if the steam vent mechanism is simple in configuration, it must still be able to reliably and effectively vent the steam pressure inside the packaging bag to the outside.

The present invention was made in light of these circumstances, and provides a microwaveable packaging bag that uses a simple structure without the need for folded flaps (folded portions) and that can reliably and effectively release steam generated when the contents are heated.

According to the present invention, the following inventions are provided.
[1] A packaging bag for use in a microwave oven, made of a flexible film formed into a bag shape, the packaging bag having a peripheral surface portion, the peripheral surface portion having first and second surfaces facing each other, an opening that opens upward, and an opening/closing member configured to open and close the opening, the opening/closing member having a pair of engaging members consisting of a first engaging member and a second engaging member, the first engaging member being heat-sealed to the first surface, and the upper and lower sides of the region where the second engaging member faces the second surface, sandwiching the engaging position with the first engaging member, are defined as the upper region and the lower region, respectively, the upper region has a portion where the welding strength per unit width between the second engaging member and the second surface is relatively small, and in a region that overlaps in the vertical direction with the portion in the lower region, the second engaging member and the second surface are not heat-sealed or are heat-sealed so that the welding strength per unit width is smaller than that of the portion in the lower region.
[2] The packaging bag according to [1], wherein the upper region comprises an upper central region in the center of the left-right direction of the packaging bag and upper end regions located on both sides of the upper central region, the second engaging member is heat-sealed to the second surface in both the upper central region and the upper end regions, and the upper central region has a smaller welding strength per unit width than the upper end regions, the lower region comprises a lower central region in the center of the left-right direction of the packaging bag and lower end regions located on both sides of the lower central region, the second engaging member is heat-sealed to the second surface in the lower end regions, and the second engaging member is not heat-sealed to the second surface in the lower central region or is heat-sealed so that the welding strength per unit width is smaller than that of the upper central region, and the lower central region overlaps with the upper central region in the up-down direction of the packaging bag and is wider than the upper central region in the left-right direction of the packaging bag.
[3] The packaging bag according to [2], wherein the length of the lower central region in the left-right direction of the packaging bag is 1.5 times or more the length of the upper central region.
[4] The packaging bag according to [2] or [3], wherein the second engaging member is not heat-welded to the second surface in the lower central region.
[5] A packaging bag according to any one of [2] to [4], wherein the lower central region is configured to cover the entire left-right area of the inside of the packaging bag.

According to the present invention, microwave-safe packaging bags do not require the addition of flaps (gable portions) in a folded shape, and instead use a simple structure to reliably and effectively release steam generated when the contents are heated. Therefore, microwave-safe packaging bags can be manufactured even using a bag-making machine that does not have the functionality to add flaps (gable portions) to packaging bags.

1 is a perspective view of a packaging bag 1 according to a first embodiment of the present invention, with contents contained therein. 2 is a plan view of the packaging bag 1 of FIG. 1. FIG. 3A is a cross-sectional view taken along line AA in FIG. 2, FIG. 3B is an enlarged view of region B in FIG. 3A, and FIG. 3C shows the state in which the opening/closing member 23 in FIG. 3B is open. 10A and 10B are views showing the welded state of an upper region 23a3 and a lower region 23a4 of a base 23a1 of a front side engaging member 23a. Fig. 5A is a side view of the peripheral wall film 20b, and Fig. 5B is a diagram showing a state in which a part of the peripheral wall film 20b has been cut and the bottom film 20a has been inserted into the cut portion. Figure 6A is a diagram showing how the peripheral wall film 20b and the bottom film 20a are welded together to manufacture the packaging bag 1, and Figure 6B is a diagram showing the state in which the opening and closing member 23 has been inserted between the front portion 3 and the back portion 4. Figure 7A shows the state in which the front side seal bar 10a and the rear side seal bar 10b are used to weld the peripheral wall film 20b, the front side engaging member 23a, and the rear side engaging member 23b, and Figure 7B is an oblique view showing the general configuration of the front side seal bar 10a. Figure 8A is a diagram explaining the contact state between the front seal bar 10a and the peripheral wall film 20b in the upper region 23a3, Figure 8B is a diagram explaining the contact state between the front seal bar 10a and the peripheral wall film 20b in the lower region 23a4, and Figure 8C is a diagram showing the welding state in the upper region 23a3 and lower region 23a4 of the base 23a1 of the front engagement member 23a. 9A is a cross-sectional plan view of the vicinity of the opening/closing member 23 showing the state in which heated steam is discharged from the packaging bag 1, and FIG. 9B is a cross-sectional side view showing the state in which heated steam is discharged from the packaging bag 1. FIG. 10 is a perspective view of a packaging bag 1 according to another embodiment of the present invention, in which an opening/closing portion 24 is provided on the upper side of an opening/closing member 23 . FIG. 10 is a diagram showing another embodiment of the present invention in which a fixed portion S5 is provided between a strong seal area S1 and a weak seal area S2.

The following describes embodiments of the present invention. The various features shown in the embodiments below can be combined with each other. Furthermore, each feature can be an independent invention.

1. First Embodiment 1-1. Structure of Packaging Bag 1 As shown in FIGS. 1 to 3C, packaging bag 1 in this embodiment of the present invention is a free-standing packaging bag for use in a microwave oven, in which a flexible film is formed into a bag shape. Packaging bag 1 has a bottom portion 2 and a peripheral portion 21 extending from bottom portion 2. Peripheral portion 21 has a front portion 3 and a back portion 4 facing each other, and an opening 22 that opens upward. Front portion 3 and back portion 4 are welded to each other at their left and right ends (hereinafter also referred to as side ends). Bottom portion 2 is welded (heat sealed) to front portion 3 and back portion 4. In this way, the bottom portion 2, front portion 3, and back portion 4 are welded to each other, forming the film into a bag shape.

In this disclosure, the top, bottom, left, and right of Figure 2 will be described as the top, bottom, left, and right of the packaging bag 1. Specifically, the bottom surface 2 side will be the lower side, and the front surface 3 (and back surface 4) side will be the upper side. Furthermore, the left and right sides when the front surface 3 is placed in front will be the left and right sides of the packaging bag 1. Furthermore, the front surface 3 side will be the front side, and the back surface 4 side will be the rear side.

As shown in Figures 1 to 3C, an opening/closing member 23 is provided on the peripheral surface 21 of the packaging bag 1.

As shown in Figures 3B and 3C, the opening/closing member 23 is configured to be able to open and close the opening 22. The opening/closing member 23 includes a front-side engaging member 23a and a rear-side engaging member 23b that can engage with each other. The front-side engaging member 23a is fixed to the inner surface of the front portion 3. The rear-side engaging member 23b is fixed to the inner surface of the rear portion 4. The welded state between the front-side engaging member 23a and the front portion 3, and the fixed state (welded state) between the rear-side engaging member 23b and the rear portion 4 will be described later.

As shown in Figure 3C, the front-side engaging member 23a has a base 23a1 and a hook portion 23a2 protruding from the base 23a1. The rear-side engaging member 23b has a base 23b1 and a hook portion 23b2 protruding from the base 23b1.

Base 23a1 is fixed to front surface 3 via upper region 23a3 and lower region 23a4. Base 23b1 is fixed to back surface 4 via upper region 23b3 and lower region 23b4. Hook portions 23a2 and 23b2 can be engaged and disengaged with each other. As shown in Figure 3B, opening 22 is closed when hook portions 23a2 and 23b2 are engaged, and opening 22 is opened when hook portions 23a2 and 23b2 are disengaged from each other as shown in Figure 3C.

The upper regions 23a3, 23b3 and the lower regions 23a4, 23b4 are respectively positioned above and below the engagement position between the front-side engaging member 23a and the rear-side engaging member 23b (the engagement position of the hook portions 23a2, 23b2).

As shown in Figure 4, in the upper region 23a3, the base 23a1 is heat-sealed to the front surface 3 in strong seal regions S1 (corresponding to the upper end regions) on both sides of the packaging bag 1, excluding the center in the left-right direction. The base 23a1 is weakly welded to the front surface 3 in a weak seal region S2 (corresponding to the upper center region) in the center. The weak seal region S2 is configured so that the weld strength per unit width is smaller than that of the strong seal region S1, so that it can be peeled off by the steam pressure generated when the contents of the packaging bag 1 are heated.

On the other hand, in the lower region 23a4, the base portion 23a1 is heat-sealed to the front surface portion 3 in strong seal regions S3 (corresponding to the lower end regions) at both left and right ends of the packaging bag 1. Furthermore, the base portion 23a1 is not welded to the front surface portion 3 in the unsealed region S4 (corresponding to the lower central region) sandwiched between the strong seal regions S3.

In Figure 4, the left-right length of the strong seal area S3 roughly corresponds to the weld width of the left-right ends of the front and back sections 3 and 4 (the left-right length of the side edge welds 12, described below). Therefore, an unsealed area S4 is provided across the entire left-right area of the inside of the packaging bag 1. However, the configurations of the strong seal area S3 and the unsealed area S4 are not limited to those shown in Figure 4. The unsealed area S4 is intended to apply a concentrated force in the peeling direction to the weak seal area S2 when the packaging bag 1 is heated, so the left-right length of the unsealed area S4 only needs to be greater than the left-right length of the weak seal area S2.

The unsealed area S4 is positioned so as to overlap the weak seal area S2 in the vertical direction, and is configured to be wider than the weak seal area S2 in the horizontal direction. Considering the need to efficiently apply a peeling force to the weak seal area S2 when the packaging bag 1 expands due to the pressure of the heated steam, it is preferable that the horizontal length of the unsealed area S4 be at least 1.5 times the horizontal length of the weak seal area S2. The horizontal length of the unsealed area S4 can be, for example, 1.5 to 5 times the horizontal length of the weak seal area S2. Specifically, the horizontal length of the unsealed area S4 can be, for example, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, or 5 times the horizontal length of the weak seal area S2, or it can be any ratio within a range between any two of the numerical values exemplified here.

The unwelded portion in the unsealed region S4 is preferably provided so as to extend from the lower end of the base 23a1 to the upper end of the hook 23a2. In other words, in the unsealed region S4, the base 23a1 is preferably welded to the front surface 3 only in the portion above the hook 23a2. By configuring it in this way, when the packaging bag 1 expands, a force that attempts to peel the base 23a1 of the front-side engaging member 23a from the front surface 3 is more easily applied to the weak seal region S2.

By providing such a large unsealed portion in the lower region 23a4, when the packaging bag 1 expands, the force required to break the seal is more likely to be concentrated on the weak seal region S2 in the upper region 23a3. As a result, separation between the base portion 23a1 and the front surface portion 3 is promoted in the weak seal region S2, allowing the steam pressure inside the packaging bag 1 to be reliably and efficiently released to the outside.

On the other hand, as described above, the base portion 23b1 is fixed to the back portion 4 via the upper region 23b3 and the lower region 23b4. Although not shown in the figures, the base portion 23b1 is heat-sealed to the back portion 4 over the entire left-right area of the packaging bag 1 in the upper region 23b3 and the lower region 23b4. The heat-sealing between the base portion 23b1 and the back portion 4 is similar to the heat-sealing in the strong seal region S1 described above.

In this embodiment, the rear-side engaging member 23b corresponds to the first engaging member of the present invention, and the front-side engaging member 23a corresponds to the second engaging member of the present invention. Furthermore, the rear portion 4 corresponds to the first surface, and the front portion 3 corresponds to the second surface. However, this is not limited to this, and the present invention can be suitably implemented even if the front-side configuration and the rear-side configuration are interchanged.

Figure 2 is a diagram showing the packaging bag 1 in a plan view. "Plan view" means that the packaging bag 1 is flattened without any contents inside and viewed from a direction perpendicular to the front surface 3 of the packaging bag 1. As shown in Figure 2, the packaging bag 1 is formed so as to be symmetrical with respect to the center line in the left-right direction.

The vertical length H1 of the packaging bag 1 can be, for example, 12 to 25 cm. Specific examples of H1 include 12, 12.5, 13, 13.5, 14, 14.5, 15, 15.5, 16, 16.5, 17, 17.5, 18, 18.5, 19, 19.5, 20, 20.5, 21, 21.5, 22, 22.5, 23, 23.5, 24, 24.5, and 25 cm, and may be within a range between any two of the values exemplified here.

The side edges of the packaging bag 1 are provided with side edge welds 12 that weld the front portion 3 and the back portion 4 together. This secures the front portion 3 and the back portion 4 in the front-to-rear direction. Furthermore, the bottom edge of the packaging bag 1 is provided with bottom edge welds 13 that weld the bottom portion 2 to the front portion 3, and the bottom portion 2 to the back portion 4.

The lower end welded portion 13 is the area below the center line E, and welds the bottom portion 2 to the front portion 3, and the bottom portion 2 to the back portion 4 at the side and bottom ends of the packaging bag 1 (areas surrounded by dashed lines in Figure 2).

The manufacturing procedure for the packaging bag 1 will be briefly explained below with reference to Figures 5A to 6B.

First, as shown in Figure 5A, one peripheral wall film 20b is folded.

Next, as shown in Figures 5A and 5B, the bottom film 20a, folded into a V shape, is inserted into the open side of the folded peripheral wall film 20b. Next, as shown in Figures 5B to 6A, the bottom film 20a and peripheral wall film 20b are welded together, and the end opposite the welded portion is cut away to form the bottom portion 2, front portion 3, and back portion 4.

Next, as shown in Figure 6B, an opening/closing member 23 is inserted between the front portion 3 and the back portion 4 near the cutout (near the upper ends of the front portion 3 and the back portion 4), and the opening/closing member 23 is fixed to the inner surface of each of the front portion 3 and the back portion 4. Here, the opening/closing member 23 is inserted after the bottom film 20a and the peripheral wall film 20b are welded, but the opening/closing member 23 may also be inserted before the bottom film 20a. Furthermore, the processes of welding the bottom film 20a and the opening/closing member 23 to the peripheral wall film 20b may be performed separately, or may be performed simultaneously.

Then, the front portion 3 and the back portion 4 are welded together to form the side edge welds 12. When the side edge welds 12 are formed, the opening/closing member 23 is also crushed and welded, forming the strong seal area S3.

Here, the bottom film 20a and the peripheral wall film 20b are preferably laminated films having a base layer and a sealant layer, and it is even more preferable that an adhesive layer and a printed layer are provided between the base layer and the sealant layer.

The base layer is arranged so that it is exposed on the outer surface of the packaging bag 1, and the sealant layer is arranged so that it is exposed on the inner surface of the packaging bag 1. The sealant layers are welded (heat sealed) together to form a welded portion.

The substrate layer is made of a material that is strong and highly impact resistant. Examples of materials that can be used for the substrate layer include polyamide, polyolefin, polyethylene, and polyester.

The adhesive layer is a layer that adheres the base layer and sealant layer together so that they are laminated together.

The sealant layer can be formed from a resin with excellent weldability. The sealant layer can be formed from polyolefin resins such as polyethylene, polypropylene, ethylene-vinyl acetate copolymer, and ethylene-propylene block copolymer. More specifically, unstretched polypropylene and linear low-density polyethylene can be used. The film that makes up the sealant layer is preferably one that can be cut linearly in the machine direction.

As an example, in this embodiment, the structure is as follows: base layer: oriented nylon (25 μm) / printing layer / adhesive layer (dry laminate) / sealant layer: LLDPE (60 μm).

Next, using Figures 7A to 8C, we will explain in more detail how the opening/closing member 23 shown in Figure 6B is fixed to the front portion 3 and rear portion 4.

As shown in Figure 7A, the front-side engaging member 23a is heat-sealed by the front-side seal bar 10a connected to the front-side heater. Meanwhile, the rear-side engaging member 23b is heat-sealed by the rear-side seal bar 10b connected to the rear-side heater.

As shown in Figure 7B, the front seal bar 10a has multiple regions (10a1, 10a2, 10a3, 10a4) of different heights. The multiple regions (10a1, 10a2, 10a3, 10a4) are designed to have different pressing forces during heat sealing and different heat seal strengths (welding strength per unit width). For ease of explanation, in Figure 7B, the area of the peripheral wall film 20b (corresponding to the front portion 3) that corresponds to the size of a single packaging bag 1 is hatched.

As shown in Figure 7A, during the heat welding process, a heat-resistant sheet 11 made of fluororesin or the like is placed between the front engaging member 23a and the rear engaging member 23b, and the peripheral wall film 20b (corresponding to the front portion 3), the front engaging member 23a, the rear engaging member 23b, and the peripheral wall film 20b (corresponding to the rear portion 4) are sandwiched and welded using the front sealing bar 10a and the rear sealing bar 10b.

As shown in FIG. 8A, the area for heat-sealing the upper region 23a3 of the front seal bar 10a includes a weak seal area 10a3 and a strong seal area 10a4. The weak seal area 10a3 is located in a position corresponding to the center of the packaging bag 1 in the left-right direction. The weak seal area 10a3 is configured to be approximately 0.5 mm lower in height than the strong seal area 10a4. The difference in height between the weak seal area 10a3 and the strong seal area 10a4 is, for example, 0.3 to 0.7 mm. Specific examples of this difference in height are 0.3, 0.4, 0.5, 0.6, and 0.7 mm, and may be within a range between any two of the values shown here.

As shown in FIG. 8B, the area for heat-sealing the lower region 23a4 of the front seal bar 10a includes a strong seal region 10a1 and an unsealed region 10a2. The unsealed region 10a2 is positioned in a position that corresponds to the entire left-right area of the inside of the packaging bag 1. The unsealed region 10a2 is configured to be approximately 1.0 mm lower in height than the strong seal region 10a1. The difference in height between the unsealed region 10a2 and the strong seal region 10a1 is, for example, 0.8 or more. The value of this difference in height is, for example, 0.8 to 1.3 mm, and more specifically, for example, 0.8, 0.9, 1.0, 1.1, 1.2, or 1.3 mm, and may be within a range between any two of the values exemplified here.

By using the front seal bar 10a configured as shown in Figures 8A and 8B, a weak seal area S2 with steam venting function can be formed in the center of the upper area 23a3, as shown in Figure 8C. Furthermore, the strong seal areas S3 at both ends of the lower area 23a4 can be firmly heat-sealed, while the unsealed areas S4 sandwiched between the strong seal areas S3 can remain unsealed.

As a result, as shown in Figures 9A and 9B, steam generated when the contents of packaging bag 1 are heated in a microwave oven escapes to the outside through the gap between front engaging member 23a and front portion 3, preventing excessive pressure buildup inside packaging bag 1. Because packaging bag 1 is configured in such a way that the force required to break the seal is easily concentrated in weak seal area S2 of upper region 23a3, there is no need to provide a separate steam release seal portion, etc.

The welding strength per unit width in the weak seal region S2 of the upper region 23a3 shown in Figure 8C is preferably set so that the peel strength according to JIS K6854 is approximately 10 N/15 mm width or less. The peel strength is, for example, 3 to 10 N/15 mm width, specifically 3, 4, 5, 6, 7, 8, 9, or 10 N/15 mm width, and may be within a range between any two of the values exemplified here. If the horizontal length of the weak seal region S2 is increased, it is preferable to set the peel strength to a value close to 10 N/15 mm width, and if the horizontal length of the weak seal region S2 is decreased, it is also preferable to set the peel strength to a value close to 3 N/15 mm width. The horizontal length of the weak seal region S2 is preferably 1 to 7 cm, more specifically 1, 2, 3, 4, 5, 6, or 7 cm, and may also be within a range between any two of the values exemplified here, for example, 4 cm.

On the other hand, it is preferable that the welding strength per unit width in the strong seal areas S1 and S3 of the upper region 23a3 shown in Figure 8C be, for example, a peel strength according to JIS K6854 of approximately 20 N/15 mm width. The peel strength is, for example, 15 to 30 N/15 mm width, specifically, for example, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30 N/15 mm width, and may be within a range between any two of the values exemplified here.

If steam can be reliably and effectively released from the weak seal area S2 in the upper area 23a3, there is no need to provide a separate steam release seal section or gable section in the packaging bag 1. Therefore, even if microwave oven packaging bags are manufactured using a bag making machine that does not have the function of providing gabled flaps (gable sections) on packaging bags, problems with using the microwave oven packaging bags can be prevented.

2. Other embodiments

In the packaging bag 1 described in the first embodiment, as shown in FIG. 10, a tearing section 24 may be provided above the opening/closing member 23. The tearing section 24 is a portion for opening the packaging bag 1. In this embodiment, the tearing section 24 includes a tear initiation section 24a, which serves as the starting point for tearing the peripheral surface section 21, and a printed perforation line 24b indicating the area where the opening should be cut. The packaging bag 1 may be opened by tearing the peripheral surface section 21 starting from the tear initiation section 24a, or by cutting the peripheral surface section 21 along the perforation line 24b using a cutting tool such as scissors. The tear initiation section 24a is a portion that facilitates tearing the peripheral surface section 21 and is formed, for example, by a notch or cut. One of the tear initiation section 24a and the perforation line 24b may be omitted. The tearing section 24 may also have another configuration that enables the packaging bag 1 to be opened. For example, instead of the cut lines 24b, half-cut lines extending in the circumferential direction of the peripheral surface portion 21 may be provided, or a strip of film may be arranged so as to extend in the circumferential direction of the peripheral surface portion 21. The strip of film is welded to the peripheral surface portion 21, and by grasping and pulling the end of the strip of film, it is possible to tear the peripheral surface portion 21 along the strip of film.

If the upper side of the tear-opening portion 24 is heat-sealed, the packaging bag 1 will not leak even if it is distributed with liquid seasonings or the like inside. When using the packaging bag 1, the user tears the tear-opening portion 24 and then opens the opening/closing member 23, allowing them to place ingredients such as meat or vegetables into the packaging bag 1 and mix them with the liquid seasoning or the like. The opening/closing member 23 can then be closed and the ingredients inside the packaging bag 1 can be heated by heating in a microwave oven.

Also, as shown in FIG. 11, a fixed portion S5 having a stronger weld strength per unit width than the strong seal region S1 may be provided between the strong seal region S1 and the weak seal region S2. The fixed portion S5 preferably has a weld strength per unit width of at least 30 N/15 mm width, as measured by JIS K6854. The fixed portion S5 is preferably provided so that it abuts one end of the weak seal region S2. The side where the fixed portion S5 is provided makes the seal less likely to break, while the opposite side makes the seal more likely to break. Therefore, by positioning the fixed portion S5, it is possible to control the direction in which the upper region 23a3 peels when the weak seal region S2 breaks. The fixed portion S5 can be formed, for example, by adjusting the shape of the front seal bar 10a so that the pressure applied during heat sealing is locally increased. However, the fixed portion S5 may also be formed using other methods, such as locally increasing the temperature during heat sealing.

Although the embodiments have been described above, the technical ideas of the present disclosure can also be adopted in the following aspects.
A weakly sealed region (corresponding to the lower central region) may be provided instead of the unsealed region S4 described above. If the seal in this weakly sealed region is easily broken when the packaging bag 1 expands, it will have the same effect as the unsealed region S4 described above, and will not pose a problem in practical use of the packaging bag 1. The welding strength per unit width in this weakly sealed region is preferably smaller than that of the weakly sealed region S2 (upper central region) described above, and more preferably is set to a level that is considered to be substantially unwelded (for example, a peel strength according to JIS K6854 of less than 3 N/15 mm width).
The peripheral surface portion 21 may have a pair of side surfaces between the front surface portion 3 and the rear surface portion 4. In this case, the front surface portion 3 and the rear surface portion 4 are welded to the pair of side surfaces, respectively, to form the peripheral surface portion 21 having a substantially rectangular shape.
In the above embodiment, the bottom surface portion 2 is made of a film folded into a V-shape, but this is not limited to this form and may be made of a film folded into a W-shape, for example.
The method for manufacturing the packaging bag 1 is not limited to the method described in the above embodiment.

1: Packaging bag, 2: Bottom surface, 3: Front surface, 4: Back surface, 10a: Front seal bar, 10a1: Strong seal area, 10a2: Unsealed area, 10a3: Weak seal area, 10a4: Strong seal area, 10b: Back seal bar, 11: Heat-resistant sheet, 12: Side edge welded portion, 13: Bottom edge welded portion, 20a: Bottom film, 20b: Peripheral wall film, 21: Peripheral surface, 22: Opening, 23: Opening/closing member, 23a: Front side fastener Joint member, 23a1: base, 23a2: hook portion, 23a3: upper region, 23a4: lower region, 23b: rear engaging member, 23b1: base, 23b2: hook portion, 23b3: upper region, 23b4: lower region, 24: opening portion, 24a: tear initiation portion, 24b: perforation line, B: region, E: center line, S1: strong seal region, S2: weak seal region, S3: strong seal region, S4: unsealed region, S5: adhesive area

Claims (5)

A packaging bag for a microwave oven, in which a flexible film is formed into a bag shape,
The packaging bag has a peripheral surface portion,
the peripheral surface portion includes a first surface and a second surface facing each other, an opening portion that opens upward, and an opening/closing member configured to be able to open and close the opening portion,
the opening/closing member has a pair of engaging members consisting of a first engaging member and a second engaging member,
the first engaging member is heat-welded to the first surface;
In the region where the second engaging member faces the second surface, the upper and lower sides of the engaging position with the first engaging member are defined as an upper region and a lower region, respectively.
the upper region has a portion where the welding strength per unit width between the second engaging member and the second surface is relatively small,
In a region that overlaps vertically with the location in the lower region, the second engaging member and the second surface are not heat-welded or are heat-welded so that the welding strength per unit width is smaller than that at the location. The packaging bag according to claim 1,
The upper region includes an upper central region in the center of the packaging bag in the left-right direction, and upper end regions located on both sides of the upper central region,
the second engaging member is heat-welded to the second surface in both the upper central region and the upper end regions;
The upper central region has a smaller welding strength per unit width than the upper end regions,
The lower region includes a lower central region in the center of the packaging bag in the left-right direction, and lower end regions located on both sides of the lower central region,
the second engaging member is heat-welded to the second surface at both lower end regions, and is not heat-welded to the second surface at the lower central region, or is heat-welded to the second surface at the lower central region so that the welding strength per unit width is smaller than that at the upper central region;
The packaging bag is configured so that the lower central region overlaps with the upper central region in the vertical direction of the packaging bag and is wider than the upper central region in the left-right direction of the packaging bag. The packaging bag according to claim 2,
A packaging bag, wherein the length of the lower central region in the left-right direction of the packaging bag is 1.5 times or more the length of the upper central region. The packaging bag according to claim 2 or claim 3,
A packaging bag, wherein the second engaging member is not heat-sealed to the second surface in the lower central region. The packaging bag according to claim 4,
A packaging bag, wherein the lower central region is configured to cover the entire left-right area of the inside of the packaging bag.