Packaging bags and packaged foods

Abstract

To provide a packaging bag and a packaged food capable of appropriately suppressing burst sound and discharging steam generated by microwave heating.SOLUTION: A packaging bag 101 has a vapor port forming resin layer 4 for lamination strength adjustment on a front sheet 1A so that a steam port 11 for discharging steam generated by microwave heating of a food F from an accommodation space 7 is formed in a part of a gusset seal portion 9. The steam port forming resin layer 4 crosses the gusset seal portion 9 from the inner side to the outer edge of the gusset seal portion 9, and is formed so as to satisfy the conditional expressions: b<a, 20≤a≤60, and 10≤b≤40 (a is width (mm) of the steam port forming resin layer 4 at the inner edge of the gusset seal portion 9, b is width (mm) of the steam port forming resin layer 4 at the outer edge of the gusset seal portion 9).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a packaging bag and a packaged food, and more particularly to a packaging bag for heating in a microwave oven made of a heat-sealed laminated film, and a packaged food for heating in a microwave oven produced by sealingly packaging a food in the packaging bag. [Background technology]

[0002] Prepackaged foods for microwave heating, which contain retort foods, frozen foods, etc., are widely used. When these prepackaged foods are heated in a microwave oven, the moisture in the contents evaporates as the food is heated, and the generated steam increases the pressure inside the packaging bag. If the pressure inside the packaging bag increases, the bag may break, causing the contents to splash out and soil the inside of the microwave oven. Therefore, a packaging bag equipped with a steam release mechanism has been proposed to allow the steam generated during microwave heating to escape outside the packaging bag (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2004-115053 A [Patent Document 2] JP 2004-115056 A Summary of the Invention [Problem to be solved by the invention]

[0004] When a steam vent mechanism is used, steam is released before the internal pressure of the packaging bag rises too much (i.e. the inside and outside of the packaging bag communicate and the steam is released), but popping noises can occur during this steaming. In the packaging bags described in Patent Documents 1 and 2, in order to prevent popping noises, the shape of the heat-sealed part that forms the steam vent is designed so that the stress caused by the rise in internal pressure is concentrated at a specific position in the heat-sealed part, facilitating steaming. However, if a large amount of steam is released in a short period of time, the content may be reduced in weight and its quality may change, or the packaged food may vibrate significantly during heating, causing liquid to leak from the steam vent.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and its object is to provide a packaging bag and packaged food that are capable of properly suppressing popping noises and venting steam generated during microwave heating. [Means for solving the problem]

[0006] In order to achieve the above object, a packaging bag according to a first aspect of the present invention is a packaging bag for heating in a microwave oven, which is made by heat sealing a laminated film so that a storage space for storing contents is formed inside the packaging bag, the laminate film has a steam port-forming resin layer for adjusting laminate strength so that a steam port for discharging steam generated by heating the content in a microwave oven from the storage space is formed in a part of the seal part formed by the heat seal, The steam port-forming resin layer is formed so as to traverse the seal portion from inside the inner edge to the outer edge of the seal portion and to satisfy the following conditional expressions (1) to (3). b 20≦a≦60 …(2) 10≦b≦40 …(3) however, a: Width of the steam port forming resin layer at the inner edge of the seal part (mm), b: Width of the steam port forming resin layer at the outer edge of the seal part (mm), It is.

[0007] ​The packaging bag of a second invention is the packaging bag of the first invention, wherein the steam port-forming resin layer is integrally formed so as to have a first rectangular area on the inner edge side of the sealed portion, a second rectangular area on the outer edge side of the sealed portion, and a trapezoidal area between the first rectangular area and the second rectangular area, The first and second rectangular regions are positioned so as to have sides perpendicular to the outer edge of the seal portion, and the trapezoid region is positioned so as to be adjacent to the first and second rectangular regions with sides parallel to each other.

[0008] The packaging bag of a third invention is characterized in that, in the above-mentioned second invention, the steam port-forming resin layer is formed so as to satisfy the following conditional formula (4). c1≦10 …(4) however, c1: length of the side perpendicular to the outer edge of the seal portion in the first rectangular region (mm); It is.

[0009] The packaging bag of a fourth invention is characterized in that, in the second or third invention, the steam port-forming resin layer is formed so as to satisfy the following conditional formula (5). c2≦10 …(5) however, c2: length of the side perpendicular to the outer edge of the seal portion in the second rectangular region (mm); It is.

[0010] The packaging bag of a fifth invention is characterized in that, in any one of the above first to fourth inventions, the laminate film has a laminate structure including a base layer, an adhesive layer, and a sealant layer, and the steam port-forming resin layer increases the laminate strength between the base layer and the sealant layer in a room temperature environment and decreases it in a high temperature environment.

[0011] The packaging bag of the sixth invention is a standing type packaging bag for microwave heating in any one of the first to fifth inventions, The laminated film includes a front sheet, a back sheet facing the front sheet across the storage space, and a bottom sheet forming a two-fold gusset portion between the front sheet and the back sheet, The seal portion formed by the heat seal includes a side seal portion formed between the front sheet and the back sheet, and a gusset seal portion formed between each of the front sheet and the back sheet and the bottom sheet.

[0012] The packaging bag of the seventh invention is characterized in that, in the above-mentioned sixth invention, the length in the packaging bag width direction is 130 to 160 mm, the seal width of the side seal portion is 10 mm or more, the seal width at the widthwise centre of the gusset seal portion is 10 mm or less, and the steam port-forming resin layer is located in the widthwise centre of the gusset seal portion.

[0013] The packaging bag of the eighth invention is the packaging bag of the sixth or seventh invention above, characterized in that in a horizontally placed state with the front sheet located on the upper side and the back sheet located on the lower side, the steam port-forming resin layer is located on the front sheet.

[0014] The packaging bag of a ninth invention is characterized in that, in any one of the sixth to eighth inventions, the gusset seal portion has a shape that requires registration during the heat sealing.

[0015] The packaging bag of the 10th invention, in any one of the 6th to 9th inventions above, is characterized in that the bottom sheet has a hole in the overlapping area of ​​the side seal portion and the gusset seal portion so that the front sheet and the back sheet are heat sealed.

[0016] The packaged food of the 11th invention is a packaged food for heating in a microwave oven, characterized in that it comprises a packaging bag according to any one of the first to tenth inventions above, and a food that is hermetically packaged and contained within the storage space as the contents. Effect of the Invention

[0017] According to the present invention, since the steam port-forming resin layer is formed to satisfy the predetermined conditions, it is possible to appropriately suppress popping noises and vent steam generated during microwave heating. For example, popping noises can be suppressed because steam is smoothly vented from the steam port before the internal pressure of the packaging bag becomes too high. In addition, since steam is vented little by little over time, it is possible to prevent the quality of the contents from changing due to weight loss caused by excessive steam escaping, or liquid leakage from the steam port caused by large vibrations of the packaged food during heating. [Brief description of the drawings]

[0018] [Figure 1] 1 is an external view showing one embodiment of a packaging bag and packaged food for microwave heating; [Diagram 2] 2 is a cross-sectional view taken along line L1-L1' in FIG. 1(A) and showing a portion D therein. [Diagram 3] FIG. 4 is a plan view illustrating features of the shape of the steam port-forming resin layer. [Figure 4] FIG. 2 is a plan view showing a packaging bag having a rounded convex steam port-forming resin layer. [Diagram 5] FIG. 2 is a cross-sectional view of a main portion of the packaged food of FIG. 1(B) during heating in a microwave oven. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, packaging bags, packaged foods, etc. according to embodiments of the present invention will be described with reference to the drawings. Note that the same or corresponding parts in each embodiment and specific example will be given the same reference numerals, and duplicated explanations will be omitted as appropriate.

[0020] Fig. 1 shows a schematic diagram of the overall structure of a packaging bag 101 and a packaged food 201 according to an embodiment, and Fig. 2 shows a schematic diagram of a cross-sectional structure of the packaging bag 101. In Fig. 1, (A) is a plan view showing a standing-type packaging bag 101 in a folded state, and (B) is a front view showing a packaged food 201 in which food F is sealed in the packaging bag 101. In Fig. 2, (A) is a cross-sectional view taken along line L1-L1' in Fig. 1(A), and (B) is a cross-sectional view showing part D in Fig. 2(A).

[0021] The packaging bag 101 is composed of three sheets, a front sheet 1A, a back sheet 1B, and a bottom sheet 1C, all of which are made of laminated film. The laminated film is heat sealed (thermal bonding) to form a standing pouch inside the packaging bag, so that a storage space 7 for storing food F as the contents is formed inside the packaging bag. Therefore, it can be manufactured using a general standing pouch bag making machine, and the heat sealing is performed under sealing temperature conditions within a range that does not impair the properties and functions of the product when making the bag using a continuous bag making machine that produces actual products.

[0022] The front sheet 1A and the back sheet 1B are arranged to face each other with a storage space 7 interposed therebetween, and the left and right edges of the sheets are heat-sealed in a superimposed state. The bottom sheet 1C, which forms a gusset part folded in half between the front sheet 1A and the back sheet 1B, is heat-sealed at the edges of the lower ends of the front sheet 1A and the back sheet 1B. However, the upper ends of the front sheet 1A and the back sheet 1B are left unsealed. In other words, in the packaging bag 101, the storage space 7 is formed by the side seal part 8 formed by heat sealing the front sheet 1A and the back sheet 1B, and the gusset seal part 9 formed by heat sealing each of the front sheet 1A and the back sheet 1B and the bottom sheet 1C, and an opening 10h is formed above the storage space 7.

[0023] In addition, a linear cut 8a is formed on the left and right periphery of the lower part of the side seal part 8 (above the gusset seal part 9) as a starting point when opening. The shape of this cut 8a is not limited to a linear shape, but may be a V-shape, a U-shape, or the like. The position of the cut 8a is set so that the tear direction from the cut 8a coincides with the linear easy tear direction of the laminated film. In other words, with respect to the MD direction (machine direction: flow direction of the film) and the TD direction (transverse direction: width direction of the film) in FIG. 1(A), the MD direction of the sheets 1A and 1B is set so as to coincide with the tear direction from the cut 8a.

[0024] As shown in FIG. 2(B), the laminated film (front sheet 1A, back sheet 1B, and bottom sheet 1C) constituting the packaging bag 101 is composed of a base layer 2 as an outer layer, a sealant layer 6 as an inner layer, and a printed ink layer 3, an adhesive layer 5, etc. provided therebetween. In other words, the laminated film has a laminated structure including the base layer 2, the printed ink layer 3, the adhesive layer 5, and the sealant layer 6 from the outside of the packaging bag to the inside of the packaging bag. Furthermore, in the front sheet 1A, a steam port-forming resin layer 4 for adjusting the lamination strength is formed inside the printed ink layer 3 so as to straddle the gusset seal portion 9 (FIG. 1), and a steam port 11 for discharging (steaming) steam generated by heating the contents (food F) in the microwave from the storage space 7 is formed in a part of the gusset seal portion 9. In other words, the steam port-forming resin layer 4 corresponds to the area where the steam port 11 is to be formed.

[0025] The base layer 2 is required to have the strength to withstand the loads of printing work, refrigerated / frozen storage, microwave heating, etc., and therefore it is preferable to use a synthetic resin film having excellent mechanical, physical, and chemical properties. From this viewpoint, specific examples of the base layer 2 include polyamide-based films such as biaxially oriented nylon (ONY) film (including those having oxygen barrier properties as necessary), transparent vapor-deposited polyethylene terephthalate (PET) film, etc.

[0026] The sealant layer (thermoadhesive resin layer) 6 is provided to bond two laminated films together to form a storage space 7 and seal the food F. The bonding is performed by bringing the sealant layers 6 into contact with each other and heating them. Therefore, when the bag is made, the sealant layer 6 is located at the innermost side of the packaging bag 101 (FIG. 2(B)). The sealant layer 6 can be appropriately selected according to the physical properties required for the packaging bag 101. However, in the region where the steam port-forming resin layer 4 is located, it is necessary to use a layer that will break due to steam passage, as described below.

[0027] From the above viewpoint, specific examples of the sealant layer 6 include polyethylene films such as linear low density polyethylene (LLDPE) film and low density polyethylene (LDPE) film. For example, the thickness of the LLDPE film is preferably 30 to 60 μm, and if it is thicker than this, breakage due to vapor transmission is unlikely to occur. Furthermore, as physical properties of the sealant layer 6, the breaking strength in the MD direction is preferably 0.5 to 2.5 N / 15 mm, and the tensile elongation is preferably 600% or less.

[0028] The printing ink layer 3 is formed of color ink, specific examples of which include a picture layer, a white ink layer, etc. The adhesive layer 5 is formed of, for example, a dry lamination adhesive that is generally used in the dry lamination method. Specific examples of adhesives include polyvinyl acetate adhesives, polyacrylic ester adhesives, cyanoacrylate adhesives, ethylene copolymer adhesives, cellulose adhesives, polyester adhesives, polyamide adhesives, amino resin adhesives, epoxy adhesives, polyurethane adhesives, etc.

[0029] The steam port-forming resin layer 4 is a heat-softening resin layer that has a certain strength (i.e., a certain laminate strength of the steam port-forming resin layer 4 itself) at room temperature (about 30°C) or lower, but has the property of decreasing its strength at high environmental temperatures. The environmental temperature at which the predetermined strength is maintained is usually the environmental temperature in the packaging process in which the contents are packaged, the environmental temperature in the process in which the packaging bag in which the contents are packaged is refrigerated or frozen, the environmental temperature in the distribution stage in which the contents are transported or stored in a refrigerated or frozen state, and the like, and at such environmental temperatures, the predetermined strength is maintained in the steam port-forming resin layer 4. The high environmental temperature at which the predetermined strength is decreased is the temperature that occurs when the packaging bag 101 in which the contents are hermetically packaged is heated and cooked in a microwave oven, and at such high environmental temperatures, the strength of the steam port-forming resin layer 4 is decreased. Therefore, by forming the steam port-forming resin layer 4, the laminate strength between the base layer 2 and the sealant layer 6 in the formation region is high at room temperature and low at high temperature.

[0030] As the material for the steam port-forming resin layer 4 having the above-mentioned properties, it is preferable to use a heat-softening resin (such as a release varnish) having a melting point of 60 to 90°C. Specific examples include nitrocellulose-polyamide resin, polyamide-nitrocellulose-polyethylene wax resin, and ethylene-vinyl acetate copolymer resin. By using a heat-softening resin with a melting point of 60 to 90°C, it is possible to easily cause delamination for steaming, which will be described later, in the steam port-forming resin layer 4 when cooking with heat in a microwave oven. For this reason, the coating amount of the material used for the steam port-forming resin layer 4 can be extremely small. Since no separate member such as an easily peelable tape is required, the structure is simple and easy to manufacture, and costs can be reduced.

[0031] The steam port-forming resin layer 4 is formed so as to straddle the gusset seal portion 9 as described above. That is, the steam port-forming resin layer 4 is formed so as to cross the gusset seal portion 9 from inside the inner edge of the gusset seal portion 9 to the outer edge of the gusset seal portion 9 in a part of the gusset seal portion 9 between the printing ink layer 3 and the adhesive layer 5 of the front sheet 1A. In a similar formation region, the steam port-forming resin layer 4 may be provided on the back sheet 1B or the bottom sheet 1C. However, in order to provide one steam port 11 in the gusset seal portion 9, the steam port-forming resin layer 4 is formed on only one of the front sheet 1A, the back sheet 1B, and the bottom sheet 1C. The steam port-forming resin layer 4 may be disposed not only in the gusset seal portion 9 but also in the side seal portion 8 or the top seal portion 10 as necessary.

[0032] When cooking is performed in a microwave oven, the internal pressure increases due to steam (water vapor, etc.) generated from the contents (food F), and the packaging bag 101 becomes strongly inflated. Due to the strength reduction of the steam port-forming resin layer 4 caused by the high temperature environment described above, the adjacent sealant layer 6 must maintain the internal pressure by its own strength, and as a result of receiving a large load of the internal pressure, it stretches and breaks. This is because cracks are likely to occur at the boundary between the area where the steam port-forming resin layer 4 is provided and the area where it is not provided, and in the vicinity thereof. In many cases, in the area where the steam port-forming resin layer 4 is provided, a crack occurs in the sealant layer 6 (on the side adjacent to the steam port-forming resin layer 4) at the boundary between the area where the sealant layers 6 are bonded and the area where they are not bonded (i.e., the inner edge of the gusset seal portion 9), causing a break. From the broken point, interlayer peeling progresses due to the internal pressure. In other words, peeling between the layers made of the steam port-forming resin layer 4 progresses from the inner edge of the gusset seal portion 9 or from the inner side to the outer edge of the gusset seal portion 9. Then, when the delamination reaches the outer edge of the gusset seal portion 9, the steam in the storage space 7 is released to the outside through the steam vent 11, and the internal pressure of the packaging bag 101 decreases.

[0033] The features of the shape of the steam port-forming resin layer 4 will be described with reference to Fig. 3. As shown in Fig. 3(A), when the steam port-forming resin layer 4 has a rectangular shape, the width a of the steam port-forming resin layer 4 at the inner edge of the gusset seal portion 9 and the width b of the steam port-forming resin layer 4 at the outer edge of the gusset seal portion 9 are the same size (a = b). In addition, since the steam port-forming resin layer 4 is formed so as to traverse the gusset seal portion 9 from inside the inner edge of the gusset seal portion 9 to the outer edge, the length c0 of the side of the steam port-forming resin layer 4 perpendicular to the outer edge of the gusset seal portion 9 is greater than the seal width y2 at the widthwise center of the gusset seal portion 9.

[0034] In the steam port-forming resin layer 4 shown in Fig. 3(A), if the widths a and b are small, the above-mentioned cracks are unlikely to occur in the sealant layer 6, making it difficult for steam to pass through (poor steaming). Conversely, if the widths a and b are large, cracks are likely to occur in the sealant layer 6, making steaming smooth, but the steam in the storage space 7 is released all at once, causing a loud popping noise. Furthermore, if the width b is large, the steam port 11 is also large, so there is a possibility that more steam will escape than necessary, causing a loss in volume (high concentration, drying, etc.), which may result in a change in the quality (taste, etc.) of the contents, or liquid leakage from the steam port 11. Even in the case of poor steaming, if the internal pressure of the packaging bag 101 becomes extremely high and the bag breaks, a loud popping noise will be generated similar to that described above.

[0035] Since the internal pressure of the packaging bag 101 depends on the contents (water content, etc.), which are the source of steam generation, by setting the widths a and b of the steam port-forming resin layer 4 to different sizes, it is possible to control both the ease of steam passage and the loudness of the popping sound. For example, as shown in FIG. 3(B), by making the shape of the steam port-forming resin layer 4 a trapezoid and setting the steam port-forming resin layer 4 to satisfy the condition a>b, it is possible to achieve both appropriate steam passage and suppression of popping sound. In other words, by making the width a larger, it is possible to make it easier for cracks to occur in the sealant layer 6, and to smooth steam passage. Furthermore, by making the width b smaller, the progress of peeling between the layers of the steam port-forming resin layer 4 is suppressed, and therefore the steam is not discharged all at once, and popping sound is suppressed. Moreover, the peeling between the layers of the steam port-forming resin layer 4 can be made to progress gradually, so that an extreme rise in the internal pressure is suppressed.

[0036] As shown in Fig. 3(B), when the steam port-forming resin layer 4 has a trapezoidal shape and the gusset seal portion 9 has a shape that requires alignment during heat sealing (such as a bowl shape or a boat shape), if fluctuations (for example, processing misalignment in the direction of the seal width y2) occur during the gusset seal processing or outer periphery cutting processing during bag production, the widths a and b will change. To prevent this, in the steam port-forming resin layer 4 shown in Fig. 3(C), a first rectangular area 41 located on the inner edge side of the gusset seal portion 9 and a second rectangular area 42 located on the outer edge side of the gusset seal portion 9 are formed integrally so as to be adjacent to each other, and the first and second rectangular areas 41 and 42 are positioned so as to have sides (sizes c1 and c2) perpendicular to the outer edge of the gusset seal portion 9. Even if processing misalignment occurs in the direction of the seal width y2, the first rectangular area 41 has sides with a length c1 greater than the amount of processing misalignment, so there is no change in width a, and the second rectangular area 42 has sides with a length c2 greater than the amount of processing misalignment, so there is no change in width b (stabilization of widths a and b). In other words, it is possible to accommodate processing misalignment during bag making in the relevant areas.

[0037] As shown in Fig. 3(C), when the steam port-forming resin layer 4 is composed of a combination of a first rectangular region 41 and a second rectangular region 42, the degree of delamination changes significantly at the boundary between the two rectangular regions 41, 42, and at that time, the internal pressure may rise extremely. To prevent this, the steam port-forming resin layer 4 shown in Fig. 3(D) is integrally formed to have the first rectangular region 41 on the inner edge side of the gusset seal portion 9, the second rectangular region 42 on the outer edge side of the gusset seal portion 9, and a trapezoidal region 43 between the first rectangular region 41 and the second rectangular region 42. The first and second rectangular regions 41, 42 are positioned to have sides (sizes c1, c2) perpendicular to the outer edge of the gusset seal portion 9, and the trapezoidal region 43 is positioned to be adjacent to the first and second rectangular regions 41, 42 with sides (sizes a, b) parallel to each other. Therefore, since the delamination in the trapezoidal region 43 can be caused to progress gradually, an extreme increase in the internal pressure between the first and second rectangular regions 41, 42 can be suppressed.

[0038] Fig. 4 shows a packaging bag 101 having a rounded convex steam port-forming resin layer 4. The steam port-forming resin layer 4 shown in Fig. 4 has a convex shape consisting of a combination of a first rectangular region 41 and a second rectangular region 42, similar to the steam port-forming resin layer 4 shown in Fig. 3(C). However, the boundary between the two rectangular regions 41, 42 is rounded so as to form a curve, which prevents a large change in the degree of progress of delamination at the boundary between the two rectangular regions 41, 42. Therefore, an extreme increase in internal pressure between the first and second rectangular regions 41, 42 can be suppressed.

[0039] 3(B)-(D) and 4, by satisfying the following conditional formula (A1) as described above, it is possible to achieve both appropriate steam passage and suppression of popping noise. This effect can be further increased by satisfying the following conditional formulas (A2) and (A3). b 20≦a≦60 …(A2) 10≦b≦40 …(A3) however, ​a: width (mm) of the steam port forming resin layer 4 at the inner edge of the gusset seal portion 9, b: width (mm) of the steam port-forming resin layer 4 at the outer edge of the gusset seal portion 9, It is.

[0040] If the value falls below the lower limit of conditional formula (A2), poor steam permeation is likely to occur, and if the value exceeds the upper limit of conditional formula (A2), an increase in popping noise is likely to occur. Also, if the value falls below the lower limit of conditional formula (A3), poor steam permeation is likely to occur, and if the value exceeds the upper limit of conditional formula (A3), quality changes in the contents are likely to occur.

[0041] The first and second rectangular regions 41, 42 have sides perpendicular to the outer edge of the gusset seal portion 9, and with regard to their sizes c1, c2, it is desirable to satisfy the following conditional expressions (A4) and (A5). In other words, it is desirable for the steam port-forming resin layer 4 shown in Figures 3(C), (D) and 4 to satisfy at least one of the following conditional expressions (A4) and (A5), which makes it possible to effectively deal with processing misalignment at the relevant locations during bag production. c1≦10 …(A4) c2≦10 …(A5) however, c1: length (mm) of the side perpendicular to the outer edge of the gusset seal portion 9 in the first rectangular region 41, c2: length (mm) of the side perpendicular to the outer edge of the gusset seal portion 9 in the second rectangular region 42, It is.

[0042] In the overlapping region 12 of the side seal portion 8 and the gusset seal portion 9 (FIG. 1), punch holes 9a are provided in the bottom sheet 1C so that the front sheet 1A and the back sheet 1B are heat sealed together. This makes it possible to prevent internal pressure from concentrating at the intersection of the side seal portion 8 and the gusset seal portion 9 when the packaging bag 101 expands due to heating in a microwave. This makes it possible to set the position where internal pressure is concentrated at the position of the steam port-forming resin layer 4.

[0043] In this packaging bag 101, as shown in Fig. 1(A), it is assumed that the length X in the width direction of the packaging bag is 130 to 160 mm, the seal width d of the side seal portion 8 is 10 mm or more, the seal width y2 at the width direction center of the gusset seal portion 9 is 10 mm or less, and the steam port-forming resin layer 4 has the above-mentioned predetermined coating shape and is located at the width direction center of the gusset seal portion 9. By arranging the steam port-forming resin layer 4 at the width direction center of the gusset seal portion 9 in this way, the internal pressure is concentrated at the position of the steam port-forming resin layer 4, so that it becomes possible to smoothly exhaust steam in the storage space 7 from the steam port 11. Furthermore, the seal width y2 at the width direction center of the gusset seal portion 9 is preferably 10 mm or less, but from the balance between the time required for steaming and the seal strength during transportation, storage, etc., it is more preferably 4 to 10 mm, and from the relationship with the sizes c1 and c2 of the first and second rectangular regions 41 and 42, it is more preferably 2 to 7 mm.

[0044] The steam port-forming resin layer 4 is preferably formed by gravure printing, and it is preferable to form the steam port-forming resin layer 4 in-line simultaneously with the printed ink layer 3. Since the steam port-forming resin layer 4 is formed on the front sheet 1A or back sheet 1B, which are the body material, it is possible to form it simultaneously with the printed ink layer 3 in the printing process, and it is also easy to align the bottom sheet 1C with the front sheet 1A and back sheet 1B.

[0045] The indicia (letters, pictures, etc.) formed by the printing ink layer 3 is preferably printed in an orientation in which the gusset seal portion 9 is located on the upper side. If the indicia is printed in this orientation, the indicia will be upside down when the packaging bag 101 is placed in a standing state with the gusset portion formed by the bottom sheet 1C facing down. Therefore, when the packaged food 202 is placed in a microwave oven in a standing state, the incorrect positioning can be noticed and the positioning of the packaged food 201 can be corrected to the correct horizontal position (with the front sheet 1A located on the upper side and the back sheet 1B located on the lower side).

[0046] The thickness of the steam port-forming resin layer 4 is preferably 1 μm or more and 5 μm or less. If the thickness is less than 1 μm, peeling between the layers of the steam port-forming resin layer 4 is unlikely to occur during heating in a microwave oven, and if the thickness exceeds 5 μm, there is a risk of affecting the appearance and manufacturing process. Usually, the laminated film 1 before bag making is supplied in a rolled state, and is made into a bag shape by a packaging machine. In the rolled laminated film 1, the part where the steam port-forming resin layer 4 is formed rises, and as a result, this part stretches, which may cause bag making defects and lead to a decrease in yield, or the finished appearance after bag making may be unattractive.

[0047] The laminate strength of the region where the steam port-forming resin layer 4 is provided (lamination strength between the base layer 2 and the sealant layer 6) is preferably 0.3 to 2 N / 15 mm width at environmental temperatures below room temperature, and preferably 0.3 N / 15 mm width or less at high environmental temperatures (environmental temperatures of 90°C or more).The laminate strength of the region where the steam port-forming resin layer 4 is not provided is preferably 1.5 N / 15 mm width or more at environmental temperatures below room temperature, and preferably 0.5 N / 15 mm width or more at high environmental temperatures (environmental temperatures of 90°C or more).

[0048] When an LLDPE film (30 μm thick) is used as the sealant layer 6, the heat seal strength of the region where the steam port-forming resin layer 4 is provided is preferably 7 N / 15 mm width or more at an environmental temperature below room temperature, and preferably 4 N / 15 mm width or less at a high environmental temperature (environmental temperature of 90° C. or more). The heat seal strength of the region where the steam port-forming resin layer 4 is not provided is preferably 7.0 N / 15 mm width or more at an environmental temperature below room temperature, and preferably 3 N / 15 mm width or more at a high environmental temperature (environmental temperature of 90° C. or more). It is preferable to design the heat seal strength of the region where the steam port-forming resin layer 4 is not provided to be 1 N / 15 mm width or more greater at a high environmental temperature (environmental temperature of 90° C. or more).

[0049] When producing a packaged food 201, food F (expected contents: frozen or chilled products, fried chicken, etc.) is filled through the opening 10h into the storage space 7 of the packaging bag 101 with the side seal portion 8 and the gusset seal portion 9 formed. Then, as shown in FIG. 1(B), the top seal portion 10 is formed by heat sealing the front sheet 1A and the back sheet 1B, and a process such as retort heating is performed as necessary to obtain a packaged food 201 for microwave heating, hermetically packaged with the food F contained in the storage space 7. Note that the use of the packaging bag 101 is not limited to retort use. Depending on the specific sterilization process, distribution form, etc., uses include boiling sterilization at a lower temperature (100°C or less) than retort use, hot pack use in which the inner surface of the packaging bag is sterilized only by heating the contents, and freezing use in which the food is distributed without heat treatment, etc.

[0050] Figure 5 shows a cross-sectional structure of a main part of packaged food 201 during microwave heating. When food F is to be eaten, packaged food 201 is placed horizontally in a microwave oven with front sheet 1A on the upper side and back sheet 1B on the lower side, and heated. In packaging bag 101, an internal pressure opening type steam release mechanism is formed by steam port-forming resin layer 4 located on front sheet 1A, and steam V (Figure 5) within storage space 7 can be released to the outside of the packaging bag during microwave heating, so that packaged food 201 is in a sealed packaged state before microwave heating.

[0051] When food F generates steam V due to microwave heating, the internal pressure of the packaging bag 101 increases. The sealant layer 6 stretches and breaks due to cooperation with the steam port-forming resin layer 4 (reduction in laminate strength), and delamination progresses from the broken point. When the delamination reaches the outer edge of the gusset seal portion 9, the high-temperature, high-pressure steam V in the storage space 7 is exhausted from the steam port 11 to the outside of the packaging bag 101 (arrow mv in Figure 5), reducing the pressure in the storage space 7. When heating in the microwave oven is finished, the top of the packaging bag 101 breaks at the cut 8a (Figure 1) to open the packaged food 201, and the food F in the storage space 7 can be transferred to a dish.

[0052] As described above, the steam port-forming resin layer 4 is formed so as to satisfy the conditional expressions (A1) to (A3) and the like, and therefore it is possible to appropriately suppress popping noises and exhaust the steam V generated during microwave heating. For example, the steam V is smoothly exhausted from the steam port 11 before the internal pressure of the packaging bag 101 becomes too high, so popping noises can be suppressed. In addition, because the steam V is exhausted little by little over time, it is possible to prevent the quality of the food F from changing due to weight loss caused by more steam V than necessary escaping, and to prevent the packaged food 201 from vibrating significantly during heating, causing liquid leakage from the steam port 11.

[0053] The steam port-forming resin layer 4 that satisfies the above-mentioned conditional expressions (A1) to (A3) is not limited to the standing type packaging bag 101, but can also be applied to other types of packaging bags (wing type, pillow type, etc.). For example, if the steam port-forming resin layer 4 is provided so that the steam port 11 is formed in the wing seal part of a wing pouch or the center seal part of a pillow pouch, the same effect can be obtained as when the steam port-forming resin layer 4 is provided in the gusset seal part 9. Furthermore, as described above, the position of the steam port-forming resin layer 4 is not limited to the gusset seal part 9, so the same effect can be obtained even if the position is changed appropriately.

[0054] Therefore, the packaging bag 101 according to this embodiment can be generalized to a configuration in which a laminate film has a steam port-forming resin layer for adjusting lamination strength so that a steam port is formed in part of the sealed part formed by heat sealing, and the steam port-forming resin layer traverses the sealed part from inside the inner edge to the outer edge, and is formed so as to satisfy the following conditional expressions (1) to (3). b 20≦a≦60 …(2) 10≦b≦40 …(3) however, a: Width of the steam port forming resin layer at the inner edge of the seal part (mm), b: Width of the steam port forming resin layer at the outer edge of the seal part (mm), It is.

[0055] ​With regard to the width a, it is desirable to satisfy the following conditional expression (2a): 30≦a≦40 …(2a) This conditional formula (2a) prescribes a preferable conditional range based on the above-mentioned viewpoint, among the conditional ranges prescribed by the above-mentioned conditional formula (2). Therefore, by preferably satisfying the conditional formula (2a), the above-mentioned effect can be further increased.

[0056] It is desirable for the width b to satisfy the following conditional expression (3a): 15≦b≦20 …(3a) This conditional formula (3a) prescribes a preferable conditional range based on the above-mentioned viewpoint, among the conditional ranges prescribed by the above-mentioned conditional formula (3). Therefore, by preferably satisfying the conditional formula (3a), the above-mentioned effect can be further increased.

[0057] The above conditional expressions (A4) and (A5) can also be generalized to the following conditional expressions (4) and (5). In other words, when the steam port-forming resin layer 4 has first and second rectangular regions 41, 42 as shown in Figures 3(C) and (D) and 4, it is desirable for the first rectangular region to satisfy the following conditional expression (4), and it is desirable for the second rectangular region to satisfy the following conditional expression (5). By satisfying at least one of them, it is possible to accommodate processing misalignment at the relevant location during bag production. c1≦10 …(4) c2≦10 …(5) however, c1: length of the side perpendicular to the outer edge of the seal portion in the first rectangular region (mm); c2: length of the side perpendicular to the outer edge of the seal portion in the second rectangular region (mm); It is. EXAMPLES

[0058] The packaging bag and the like embodying the present invention will now be described in more detail.

[0059] The laminated film used (front sheet 1A, back sheet 1B, bottom sheet 1C) has a general laminated structure as follows: Type 1: The structure of the base material layer 2 / printed ink layer 3 / steam port-forming resin layer 4 / adhesive layer 5 / sealant layer 6 is ON25 / pattern layer, softened resin layer / DL / LLDPE30-60. Type 2: Base layer 2 / adhesive layer 5 / intermediate layer / printed ink layer 3, steam port-forming resin layer 4 / adhesive layer 5 / sealant layer 6 includes VMPET / DL / ON / pattern layer, softened resin layer / DL / LLDPE30-60.

[0060] however, ON25: Biaxially oriented nylon film, thickness 25μm, LLDPE30~60: Linear low density polyethylene film, thickness 30~60μm, VMPET: transparent vapor-deposited polyethylene terephthalate (PET) film, DL: General dry lamination adhesive, It is.

[0061] The steam port-forming resin layer 4 had a predetermined coating shape (sample No. 1-5: combination of rectangle and trapezoid (Fig. 3(D)), sample No. 6: trapezoid (Fig. 3(B)), sample No. 7-8: rectangle (Fig. 3(A))) and was formed in the widthwise center of the gusset seal part 9 by gravure printing using nitrocellulose-polyamide resin so as to have a thickness of 1 to 5 μm and the size (mm) shown in Table 1. At this time, the steam port-forming resin layer 4 was arranged in a part of the gusset seal part 9 of the front sheet 1A (the center position in the widthwise direction of the pouch) so as to cross the gusset seal part 9 from inside the inner edge of the gusset seal part 9 to the outer edge of the gusset seal part 9.

[0062] A packaging bag 101 was produced by forming a standing pouch using sheets 1A, 1B, and 1C of Type 1. The pouch dimensions (FIG. 1(A)) were X=140 mm (width), Y=180 mm (height), y1=30 mm (gusset width), d=10 mm (seal width of side seal portion 8), and y2=10 mm (seal width at the center of the width direction of gusset seal portion 9).

[0063] Next, a microwave heating test was conducted. After forming the gusset seal portion 9 and the side seal portion 8 (FIG. 1(A)), a predetermined amount of food F was filled into the packaging bag 101 through the opening 10h, and the opening 10h was heat sealed (forming the top seal portion 10) to create a hermetically sealed state (FIG. 1(B)). The packaged food 201 was placed horizontally in the microwave oven so that the back sheet 1B was positioned on the bottom (FIG. 5), and the microwave heating was performed to check for normal steaming from the steam vent 11, etc.

[0064] The test results for the plosive sound suppression effect and weight loss suppression effect are shown in Table 1. The plosive sound suppression effect was rated as follows: ◎: no plosive sound, ○: almost no plosive sound, △: small plosive sound, ×: large plosive sound, and the weight loss suppression effect was rated as follows: ◎: no weight loss, ○: almost no weight loss, △: small weight loss, ×: large weight loss.

[0065] In sample No. 5, width a exceeded the upper limit of conditional formula (2), and a loud popping sound occurred. In sample No. 6, width b fell below the lower limit of conditional formula (3), and the steam port 11 narrowed, causing poor steaming due to clogging. As a result, a loud popping sound occurred. In addition, the steam port 11 expanded significantly during steaming, causing a large amount of weight loss due to steam escaping. In sample No. 7, delamination did not progress, causing poor steaming. As a result, a loud popping sound and a large amount of weight loss occurred. In sample No. 8, steaming was smooth, but a loud popping sound occurred and a large amount of weight loss occurred.

[0066] [Table 1] [Explanation of symbols]

[0067] 1A Front sheet (laminated film) 1B Back sheet (laminated film) 1C Bottom sheet (laminated film, gusset section) 2 Base material layer 3 Printing ink layer 4 Steam port forming resin layer 5 Adhesive layer 6 Sealant Layer 7. Containment Space 8 Side seal part 8a Cut 9 Gusset seal 9a Punch hole 10 Top seal part 10h opening 11 Steam vent 12 Overlap Area 41 First rectangular area 42 Second rectangular area 43 Trapezoidal Area 101 Packaging bags 201 Packaged foods F Food (contents) V Steam

Claims

1. A packaging bag for microwave heating, which is made by heat sealing a laminated film so that a storage space for storing contents is formed inside the packaging bag, the laminate film has a steam port-forming resin layer for adjusting laminate strength so that a steam port for discharging steam generated by heating the content in a microwave oven from the storage space is formed in a part of the seal part formed by the heat seal, the steam port-forming resin layer is formed so as to cross the seal portion from inside an inner edge of the seal portion to an outer edge thereof and to satisfy the following conditional expressions (1) to (3), b < a ... (1) 20≦a≦60 … (2) 10≦b≦20 … (3) however, a: width (mm) of the steam port-forming resin layer at the inner edge of the seal portion, b: width (mm) of the steam port-forming resin layer at the outer edge of the seal portion, and the steam port forming resin layer is integrally formed so as to have a first rectangular region on an inner edge side of the seal portion, a second rectangular region on an outer edge side of the seal portion, and a trapezoidal region between the first rectangular region and the second rectangular region, A packaging bag characterized in that the first and second rectangular regions are positioned so as to have sides perpendicular to the outer edge of the seal portion, and the trapezoidal region is positioned so as to be adjacent to the first and second rectangular regions with sides that are parallel to each other.

2. The packaging bag according to claim 1, characterized in that the steam port-forming resin layer is formed so as to satisfy the following conditional formula (4): c1≦10 … (4) however, c1: length (mm) of a side perpendicular to the outer edge of the seal portion in the first rectangular region; It is.

3. The packaging bag according to claim 1 or 2, characterized in that the steam port-forming resin layer is formed so as to satisfy the following conditional formula (5): c2≦10 … (5) however, c2: length of the side perpendicular to the outer edge of the seal portion in the second rectangular region (mm); It is.

4. The packaging bag according to any one of claims 1 to 3, characterized in that the laminate film has a laminate structure including a base material layer, an adhesive layer, and a sealant layer, and the steam port-forming resin layer increases laminate strength between the base material layer and the sealant layer in a room temperature environment and decreases it in a high temperature environment.

5. A standing type packaging bag for microwave heating, The laminated film includes a front sheet, a back sheet facing the front sheet across the storage space, and a bottom sheet forming a gusset portion folded in half between the front sheet and the back sheet, The packaging bag according to any one of claims 1 to 4, characterized in that the seal portion formed by the heat seal includes a side seal portion formed by the front sheet and the back sheet, and a gusset seal portion formed by each of the front sheet and the back sheet and the bottom sheet.

6. The packaging bag according to claim 5, characterized in that the length in the packaging bag width direction is 130 to 160 mm, the seal width of the side seal portion is 10 mm or more, the seal width at the widthwise center of the gusset seal portion is 10 mm or less, and the steam port-forming resin layer is located at the widthwise center of the gusset seal portion.

7. 7. The packaging bag according to claim 5, wherein, in a horizontally placed state in which the front sheet is located on the upper side and the back sheet is located on the lower side, the steam port-forming resin layer is located on the front sheet.

8. 8. The packaging bag according to claim 5, wherein the gusset seal portion has a shape that requires registration during the heat sealing.

9. The packaging bag according to any one of claims 5 to 8, characterized in that the bottom sheet has a hole so that the front sheet and the back sheet are heat sealed in the overlapping area of ​​the side seal portion and the gusset seal portion.

10. A packaged food for heating in a microwave oven, comprising the packaging bag according to any one of claims 1 to 9, and a food that is hermetically packaged and contained within the storage space as the contents.

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